September 8, 2008

General Chemistry (Part 3): Thermochemistry

For all students of XI grade, read the following questions carefully, choose one question, give your answer here but once the question has been answered, right or wrong, you can not answer it. Just write a final answer, you don't need to write stepwise. For the last five answers, you may change your answer twice, if the first answer is false.


1) What is thermochemistry exactly?

2) Why do we learn thermochemistry?

3) Give 2 examples of thermochemistry applications in daily life.

4) State a thermochemical equation if ammonium chromate (solid) formation releases 1806.7 kJ/mole of energy.

5) 130 grams acetylene (C2H2) can raise 20 liters of water from 200C to 1000C. Calculate enthalpy change of water and state its thermochemical equation if known density of water = 1 gr/ml and heat capacity of water = 1 J/gr.0C.

6) Known the enthalpy change of ethylene and ethane formations in the manner are 51,8 kJ and 64,4 kJ, what heat will be released by ethylene produces ethane?

7) By using bond energy data in your text book, calculate how much heat will be included to react ethylene and chlorine form ethyl chloride and chloric acid? Please write the bond energy of each substance.

8) Known the following thermochemical equations:
XO2 + CO -® XO + CO2 DH = - 20 kJ
X3O4 + CO -® 3 XO + CO2 DH = + 6 kJ
3 X2O3 + CO -® 2 X3O4 + CO2 DH = - 12 kJ
Calculate the enthalpy change for the following equation:
2 XO2 + CO -® X2O3 + CO2

9) Explain latent heat and sensible heat.

10) What is 1 Btu (British Thermal Unit)? Calculate the number of joules in 1 Btu of heat.

11) What does Hess' Law state and give one example to explain your answer (you may use an example from daily life or even everywhere).


12) The natural gas in methane reacts with oxygen to give carbon dioxide and water. Calculate the heat given off when 0.010 mole of methane reacts with excess oxygen in a bomb calorimeter if the temperature of 1.00 kilogram of water in the bath surrounding the bomb increases by 1.918 0C.

13) How do we measure the enthalpy of a reaction? Explain your answer sharply.

14) What are differences between an exothermic reaction and an endothermic reaction?

15) If a reaction can not go spontaneously what you will do? Explain your answer by giving an example of each way.

16) Predict which of the following substances should have an enthalpy of formation equal to zero:
(a) Hg (l)
(b) Br2 (g)
(c) H (g)
Give your reason.

17) What value of heat will be included in the following blank enthalpy change?



















18) How much heat is given off when 1 mole of nitrogen reacts with 2 moles of oxygen to give 2 moles of nitrogen oxide gas, if for the given balanced reaction is 33.2 kJ/mole of nitrogen oxide?

19) Explain why there is only one value for the standard enthalpy of reaction for a chemical reaction whereas there can be many different values for the enthalpy of reaction.

20) Use the standard enthalpies of formation in your text book to determine whether heat is given off or absorbed when limestone (calcium carbonate) is converted to lime (calcium oxide) and carbon dioxide. Write the heat value included.

21) Use bond dissociation enthalpies to estimate the enthalpy of reaction for the combustion of carbon sulfide in the phase gas to produce carbon dioxide and sulfur dioxide.

22) Calculate the standard enthalpy change for magnesium in the solid phase reacts with fluorine in the gas phase to create magnesium fluoride in the solid phase, assuming that 1.00 gram of magnesium gives off 46.22 kJ of heat when it reacts with excess fluorine.

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114 Comments:

Anonymous Anonymous said...

NAME : M.SIDQI HADYAN
CLASS : XI IPA 6


Latent heat is the total of energy in form of heat released or absorbed by substance during change of phase, like gas, liquid, and solid.

Sensible heat is the energy in the potential energy in the thermal energy form or heat. In the atmospheres, large-scale transport of heat from the tropics to the poles is affected by sensible heat in the form of warm air moving toward the poles.

September 09, 2008  
Anonymous Anonymous said...

Name : Natasia
Class : XI PSIA 6

8)
2XO2 + CO -> X2O3 + CO2
the enthalpy change (∆H) = - 40 kJ

September 10, 2008  
Anonymous Anonymous said...

Name : Aini Nur Syafa'ah
Class: XI PSIA 6

(10)
British Thermal Unit is a unit of energy used in the power, steam generation, heating and air conditioning industries. In North America, the term "BTU" is used to describe the heat value (energy content) of fuels and also to describe the power of heating and cooling systems.

It is unit of heat defined generally as the quantity of heat required to raise the temperature of one pound of water one degree Fahrenheit.

1 BTU = 1055.05585 joules
= 1055.06 joules

September 10, 2008  
Anonymous Anonymous said...

(8)
Name : Widya Tria Kirana
Absen : 22

2XO2 + 2CO -> 2XO + 2CO2 ∆H = -20 ( 2 )∆H = -40 kJ
2XO + 2/3CO2 -> 2/3M3O4 + 2/3 CO ∆H = 2/3 (-6) ∆H = -4 kJ
2/3M3O4 + 1/3CO2 -> M2O3 + 2/3 CO ∆H = 12 : 3 ∆H = 4kJ
_________________________________ +

2XO2 + 2CO -> X2O3 + CO2 ∆H = -40 kJ

so, the ∆H is -40 kJ

September 10, 2008  
Anonymous Anonymous said...

(9)

Name : Widya Tria Kirana
Absen : 22

Sensible heat
When an object is heated, its temperature rises as heat is added. The increase in heat is called sensible heat. Similarly, when heat is removed from an object and its temperature falls, the heat removed is also called sensible heat. Heat that causes a change in temperature in an object is called sensible heat.

Latent heat
All pure substances in nature are able to change their state. Solids can become liquids (ice to water) and liquids can become gases (water to vapor) but changes such as these require the addition or removal of heat. The heat that causes these changes is called latent heat. or we can say that latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase (i.e. solid, liquid, or gas), – also called a phase transition

Latent heat however, does not affect the temperature of a substance - for example, water remains at 100°C while boiling. The heat added to keep the water boiling is latent heat. Heat that causes a change of state with no change in temperature is called latent heat.

Appreciating this difference is fundamental to understanding why refrigerant is used in cooling systems. It also explains why the terms 'total capacity' (sensible & latent heat) and 'sensible capacity' are used to define a unit's cooling capacity. During the cooling cycling, condensation forms within the unit due to the removal of latent heat from the air. Sensible capacity is the capacity required to lower the temperature and latent capacity is the capacity to remove the moisture from the air.

September 10, 2008  
Anonymous Anonymous said...

(14)
Name : Widya Tria Kirana
Class : XI PSIA 6

exothermic reaction use if bond forming releases more energy than was required in the bond breaking, then overall energy is released to the surroundings. it also absorbs energy and has energy as a product
An exothermic reaction has a negative ∆H, examples: combustion, neutralisation, dissolving NaOH pellets.

endothermic reaction use if bond forming releases less energy than was required in the bond breaking, then overall energy will have been absorbed from the surroundings. It also releases energy and has energy as a reactant
An endothermic reaction has a positive ∆H, examples mixing ammonium thiocyanate and barium hydroxide crystals.

September 11, 2008  
Anonymous Anonymous said...

Fachri Ali Ramadhan
XI PSIA 6

14/what's the difference between endothermic reaction and exotermic reaction?

Endothermic reaaction : An endothermic reaction need energy or absorp an energy from environment to a system when the reaction happen.This reaction may absorp heat and the themperature of the system will increase.so,the entalphi change(∆H) will be possitive (+)
For example: when we boil water in a teapot , it will receive heat energy from the invironment.and it's themperature will increase.

Exothermic reaction : An exothermic reaction release energy from system to an environment when the reaction happen.This reaction may miss heat energy because it remove it's own energy to the environment.so,the entalphy change(∆H) will be negative (-)

For example : When we put A glass of hot water in a room themperature.it's heat will remove to the environment.and it will lost energy.so,it's themperature will decrease.

September 11, 2008  
Anonymous Anonymous said...

Name :Fachri Ali Ramadhan
Class :XI PSIA

No.3/
Example Of thermochemistry in daily life :

-when we heat water in a teapot the system will absorp heat and the themperature of the system will increase.it's example of endothermic reaction.

-when we put a glass of hot water in a room themperature,the heat will move to the environment and the themperature of a system will decrease.it's example of exothermic reaction.

-when we stand near scout fire we will feel hot.it's because the system release the heat to the environment.it's example of exothermic reaction.


i'm sorry..my answer at number 14 has answered by wtk....i don't see it before..

September 11, 2008  
Anonymous Anonymous said...

Name:Galih Putro Dwi setyo
Class: XI PSIA 6

1. thermochemistry is study of heat evolved or absorbed in chemical reactions. thermochemistry laws rest on two statements.
a. Lavoisier and laplace law
the heat exchange accompanying a transformation is equal and opposite to the heat exchange accompanying the reverse transformation.

b.hess law
the heat exchange accompanying a transformation is the same whether the process occurs in one or several steps.

September 11, 2008  
Anonymous Anonymous said...

NAME : DINDA DWITA PUSPASARI
CLASS : XI PSIA 6

½ N2 (g) + O2 (g) → NO2 (g) ∆H = -33.2 kJ/mole
N2 (g) + 2O2 (g) → 2NO2 (g) ∆H = -66.4 kJ

September 11, 2008  
Anonymous Anonymous said...

NAME : DINDA DWITA PUSPASARI
CLASS : XI PSIA 6

16)
Br2 (g) will have the entalphy of formation equal to zero, because it is in the free state. every element that is in the free state will have the entalphy formation equal to zero.

September 11, 2008  
Anonymous Anonymous said...

Name :Prayoga Seto A
Class : XI PSIA 6

4) The thermochemical equation for the formatting ammonium chromate:

N2(g)+ H2(g)+ Cr(s)+ O2(g)--> (NH4)2(CrO4) ∆Hf=-1806.7 kJ

September 13, 2008  
Anonymous Anonymous said...

Name :Annisa R. H
Class:XI IPA 6
13.
1. By using calorimetry.
We measure the changing of the temperature in calorimeter.We can determine the amount of absorbing/releasing heat by the solution and calorimeter by using the formula:
q= m. c. (Tf-Ti)
q= C. (Tf-Ti)
Beacause there's no heat that released to the enviroment, so we can conclude:
q reaction= -(q solution+q calorimeter).

2. By using Hess Law.
Hess Law have the relationship with the reactions which can reacted directly by using 2 ways or more. In this case, we can react the reactan in many ways, for example,we have one mole of reactan, we can react a half mole first, after that, we react all of reactan,or we can react the reactan directly one mole.In this case, the result will have the same value.

3. By using Entalphy formation.
For this way, we can use the data of entalphy formation from the knowing reaction that given.We can calculate it by using the formula:
∆H= ∆Hf product-∆Hf reactan.

4. By using Bonding energy
In this case, we can find the changhing of entalphy by consider the bonding energy in a table. After that, we find the entalphy changing by using the formula:
∆H=∆H(in broken bonding)-∆H (in formed bonding)

September 14, 2008  
Anonymous Anonymous said...

Name: Annisa R. H
Class: XI PSIA 6
note:
Tf= T final
Ti= T initial
Tf-Ti= ∆T

September 14, 2008  
Blogger wyd said...

the limited time to answer is next week (before holidays). plz be hurry. ad plz check all answers before you post yours. thx

September 14, 2008  
Anonymous Anonymous said...

Name : Hana Fathia Izazi
Class : XI PSIA 6

15.)

We can use catalyst to make the reaction become faster. We can also burn when the reaction is in process. For the example, when we want to change liquid water become steam or gasses.

September 15, 2008  
Anonymous Anonymous said...

name : m.ganda . r
class: XI PSIA 6



we can give catalist in order to faster the reaction. catalist is the compound or element that can make the reaction go faster, but that catalist won't lost.the example is like :
2H2O2(aq) => 2H2O(l) + O2(g). without catalist, this reaction will react slowly. to make it faster, we can give FeCl3(aq) in the reactan.

besides catalist, we can make the reaction faster or slower by heating and give pressure. the example is:
Heat :Na2S2O3 + 2HCl => 2NaCl + S + SO2 + H2O. in this reaction, the reaction will go faster two times if we raised the heat 10 degree.
Pressure: usually industries make the chemical reaction in high pressure. like making ammonia in 400 atm

September 15, 2008  
Anonymous Anonymous said...

Tarazika


10.

British thermal unit is a unit of heat equal to the amount of heat required to raise one pound of water one degree Fahrenheit at one atmosphere pressure.

1 BTU=1/0.000948 joule

September 15, 2008  
Anonymous Anonymous said...

Name : Rieszka Wellyan
Class : XI PSIA 6

(4)

½ N2 +2H2 +2Cr +4O2 --> (NH4)2CrO4
∆H=-1806.7

September 15, 2008  
Anonymous Anonymous said...

NAME : ANISA KARAMINA W
CLASS : XI.PSIA 6

17)
∆H=?
-147,1 KJ+(-107.3)KJ+(-121.7)KJ+(-411.15)KJ=-787.25
so,∆H=-787.25 KJ

September 15, 2008  
Anonymous Anonymous said...

name: m. ganda. r
class: XI PSIA 6

11.

hess law state that in thermochemistry, the way to find the entalphy changes is doesn't matter, as long the product is true. for example, it doesn't matter if you want to find the answer by looking in internet, or in the book, as long the answer is same.

September 17, 2008  
Blogger arief do with abrakadabra blogger said...

Name : Arief Hidayat
Class: XI IA 6

[number 2; Why do we learn thermochemistry?]

we learn thermochemistry for many reason.
For example, when we see the difference about the changes of Enthalpy of Incomplete Combustion between kerosene (minyak tanah)and the changes Combustion Enthalpy of LPG with the data of energy bonding . Then we know that the cost of kerosene was Rp 2000/l with density 0.8 kg/l and one 12 kg tube of LPG cost Rp 52000. we see the ratio of each mol of each substance for Rp 2000, times the change of enthalpy in one mole ...so we know in every Rp 2000 the heat of combustion that kerosene and LPG produced..we also know that LPG produce more heat than kerosene, so the government was right to instruct us to use LPG, and we can get more profit.Obviously, thermochemistry is useful in our economical life.

September 17, 2008  
Anonymous Anonymous said...

Name : EMELDA
CLASS ; XI.PSIA 6

5)
THE ENTAHLPY CHANGE = 322080 kJ

September 20, 2008  
Anonymous Anonymous said...

sorry ma'am for units for question number 5 is J so,
the enthalpy change = 322080 J

September 20, 2008  
Blogger HaDeKa MaRu said...

Name : Hendra Dwi Kusuma
Class: XI PSIA 6

18)

*)∆H for 1 mole of NO2 = -33.2 kJ/mole

*)∆H for the reaction of:

N2 + 2O2 -> 2NO2 ∆H = 2 x (-33.2 kJ/mole) = -66.4 kJ/mole

So, the heat given off for the reaction is -66.4 kJ/mole

September 21, 2008  
Blogger HaDeKa MaRu said...

sorry ma'am for my mistake, the unity is -66.4 Kj

September 21, 2008  
Anonymous Anonymous said...

Name: Tia Fitria
Class : XI PSIA 6
Answer:

6)
Reaction I: 2C(s)+ H2(g)-> C2H2(g) ΔH= 51,8
Reaction II:2C(s)+ 3H2(g)-> C2H6(g) ΔH= 64,4


C2H2(g)->2C(s)+ H2(g) ΔH= -51,8kJ
2C(s)+ 3H2(g)->C2H6(g) ΔH= 64,4 kJ
_________________________________+
C2H2(g) + 2H2(g)->C2H6(g)ΔH= 12,6 kJ

September 29, 2008  
Anonymous Anonymous said...

Alfrianda Hanafiah



22)
known : 1 gram of Mg gives off 46,22 KJ.
ask : ∆H= ?
answer : Mg + F2->MgF2


Mol Mg = massa / Ar
= 1 / 24

∆H = Q / n
= -46,22 kJ / 1/24
= -46,22 kJ x 24
= - 1109, 28 KJ

September 29, 2008  
Anonymous Anonymous said...

NAME: TRI SUSANTI (21)
CLASS: XI. PSIA 6

19.

for standard enthalpy of reaction, all reactants and product are measured in standard condition where the pressure temperature and also the number of mole are all standard. so, the different values of enthalpy reaction could happen because they are not measured in same condition. that's why the reaction only have one value for standard enthalpy reaction.

September 29, 2008  
Blogger Tarazika said...

21.

CS2+302-->CO2+2SO2

use bond energy..

(2.477+3.498,3)-(2.805+2.(2.469)=
(954+1494,9)-(1610+1876)=
2448,9-3486=-1037,1 kj/mol

September 30, 2008  
Anonymous Anonymous said...

class: 2-G
no :01

20. CaCO3(s) → CaO(s) + CO2(g)

DHO = [DHOf CaO + DHOf CO2] - [DHOfCaCO3]
= [-635.09 + (-393,509)] -[-1209.92]
= (-1208.599) + 1206.92
= - 1,679

March 08, 2009  
Anonymous Anonymous said...

Name : M. Bahrul Ulum
Class: 2B
Absen: 14

8)

2XO2 + 2CO -® 2XO + 2CO2 DH = - 40 kJ
2 XO + 2/3CO2 -® 2/3X3O4 + 2/3CO DH = - 4 kJ
2/3X3O4 + 1/3CO2-® X2O3 + 1/3CO DH = 4 kJ
_________________________________ +

2 XO2 + CO -® X2O3 + CO2 DH = -40 kJ

March 09, 2009  
Anonymous Anonymous said...

Name : A.Syafiq Yudiansyah

Class: 2.G

Absen: 3

9 )
Latent heat

in thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a chemical substance during a change of state ( solid, liquid, or gas), or a phase transition.

sensible heat

The amount of heat that, when absorbed by a substance, causes a rise in temperature.

March 09, 2009  
Anonymous Anonymous said...

sorry ma'am, I forgot to write my identity

Name : A,syafiq Yudiansyah

Class :2.G

number :3

March 09, 2009  
Anonymous Anonymous said...

A British Thermal Unit (BTU) is the amount of heat energy needed to raise the temperature of one pound of water by one degree F. This is the standard measurement used to state the amount of energy that a fuel has as well as the amount of output of any heat generating device.

1 BTU = 1054,350 J

March 09, 2009  
Anonymous Anonymous said...

Name : SEftiani
Class : 2.G
No : 24

8.

2XO2 + 2CO -® 2XO + 2CO2 DH = - 40 kJ
2 XO + 2/3CO2 -® 2/3X3O4 + 2/3CO DH = - 4 kJ
2/3X3O4 + 1/3CO2-® X2O3 + 1/3CO DH = 4 kJ
_________________________________ +

2 XO2 + CO -® X2O3 + CO2 DH = -40 kJ

March 09, 2009  
Anonymous Anonymous said...

Name : Ramadita Utami Falezia
Class : 2-G
No : 20


12) The natural gas in methane reacts with oxygen to give carbon dioxide and water. Calculate the heat given off when 0.010 mole of methane reacts with excess oxygen in a bomb calorimeter if the temperature of 1.00 kilogram of water in the bath surrounding the bomb increases by 1.918 0C.

March 09, 2009  
Anonymous Anonymous said...

Name : Ramadita Utami falezia
Class : 2-G
No : 20

10) What is 1 Btu (British thermal unit)? Calculate the number of joules in 1 Btu of heat.

The British thermal unit (BTU or Btu) is a unit of energy used in the power, steam generation, heating and air conditioning industries. In scientific contents the BTU has largely been replaced by the SI unit of energy, the joule (J ).

1 BTU = 1 054 – 1 060 J

March 09, 2009  
Anonymous Anonymous said...

Name : Dzikrina Miftahul Husna
Class: 2-G
No : 10

6).
2C (s) + H2 (g) --> C2H2 (g) DH = +51.8 kJ
2C (s) + 3H2 (g) --> C2H6 (g) DH = +64.4 kJ

C2H2 (g) + 2H2 (g) --> C2H6 (g) DH = ...?

C2H2 (g) --> 2C (s) + H2 (g) DH = -51.8 kJ
2C (s) + 3 H2 (g) --> C2H6 (g) DH = +64,4 kJ
_____________________________________________+
C2H2 (g) + 2H2 (g) --> C2H6 (g) DH = +12,6 kJ

March 09, 2009  
Anonymous Anonymous said...

Name : Dzikrina Miftahul Husna
Class : 2.G
No : 10

4).

N2(g)+4H2(g)+Cr(s)+202(g)-->(NH4)2(Cr04)(s)

DH = -1806,7 kJ/mole

March 09, 2009  
Anonymous Anonymous said...

Name : Muhammad Ramdhani
Class : 2.G
No. Absent : 17

4). Thermochemical Equation of Ammonium Chromate

Cr(s) + N2 (g) + 4H20 (g) -> (NH4)2 CrO4 (s)
∆H = -1806.7 kJ/mole

March 09, 2009  
Anonymous Anonymous said...

Name: Yesita Rizky F.P.
Class: X.G
No.: 25
A BTU is defined as the amount of heat required to raise the temperature of one pound of liquid water by one degree from 60° to 61°Fahrenheit at a constant pressure of one atmosphere.

1 BTU = 1055.56 J

March 09, 2009  
Anonymous Anonymous said...

Name: Yesita Rizky F.P.
Class: X.G
No.: 25


Thermochemistry is the study of the energy evolved or absorbed in chemical reactions and any physical transformations, such as melting and boiling. Thermochemistry, generally, is concerned with the energy exchange accompanying transformations, such as mixing, phase transitions, chemical reactions, and including calculations of such quantities as the heat capacity, heat of combustion, heat of formation, enthalpy, and free energy.

March 09, 2009  
Anonymous Anonymous said...

Name: Yesita R.F.P.
Class: X.G
No. : 25

Ma'am I sorry, I forgot to write the number of my answer. It is the answer of question no.1

March 09, 2009  
Anonymous Anonymous said...

Name : Fefy Yunitasari
Class : 2-B
Absent: 09


Number 22.

Molar mass of Mg = 24 gr/mol
∆H = -46,22 kJ/g x 24 gr/mol = -1109.28 kJ/mol

so, ∆H = -1109.28 kJ/mol

March 09, 2009  
Anonymous Anonymous said...

Name :M.Rizki Ilhami
Class :2.B

(numb 17)
-351.2+DH+121.7+107.3+498.3-(-411.12)=0
so..
-DH=787.22kJ
DH=-787.22kJ
so the enthalpy change is -787.22 kJ

March 09, 2009  
Anonymous Anonymous said...

Name:Muthia Ruchaya
Class: 2.G

no.08
2 XO2 + CO --> X2O3 + CO2 DH=-40KJ

March 10, 2009  
Anonymous Anonymous said...

name :agnes triani
class:2.G
student number : 02

number 12
CH4 + 2O2 ---> CO2 + 2H2O
Q H2O = mcDT
= 1,918 J

Q 1 mol = 0,959 J
Q CH4 = 95,9 J

March 10, 2009  
Anonymous Anonymous said...

Name : Nyimas Irina Silvani
Class: 2.G

no.06
C2H5 + 2 H2 --> C2H6 DH = +12KJ

March 10, 2009  
Anonymous Anonymous said...

name = ayu aliyah
class = 2.G
student number = 06

number 6
C2H5 + 1/2H2O ---> C2H6 +1/402 DH =-12,6 kJ
Q = 12,6 kJ

March 10, 2009  
Anonymous Anonymous said...

Name : Annisa Cendrawasih
Class: 2.G

no.07
DH = 1839.6

C-H=435
C-Cl=346
H-Cl=432
Cl-Cl=243.4

March 10, 2009  
Anonymous Anonymous said...

NAME =ayu ratnasari
class = 2.G
student number = 07

number 22
DH = 1 :1/24 x -46,22
= - 1109,28 kJ

March 10, 2009  
Anonymous Anonymous said...

Name : M. Ilham Bagus
Class : 2.G

(No. 18)

N2 + 202 -> 2NO2 enthalpy change = ...
1/2N2 + O2 -> NO2 enthalpy change = -33,2 kJ


for 1 mole N2 enthalpy change = 2 X -33,2 kJ
= -66,4 kJ

March 10, 2009  
Anonymous Anonymous said...

Name : Fahrul Rozi
Class: 2.G

Answer Number 1
thermochemistry is the study of the energy evolved or absorbed in chemical reactions and any physical transformations, such as melting and boiling. Thermochemistry, generally, is concerned with the energy exchange accompanying transformations, such as mixing, phase transitions, chemical reactions, and including calculations of such quantities as the heat capacity, heat of combustion, heat of formation, enthalpy, and free energy.

March 10, 2009  
Anonymous Anonymous said...

Name : Fahrul Rozi
Class: 2.G

Answer Number 9
Sensible heat is potential energy in the form of thermal energy or heat. The thermal body must have a temperature higher than its surroundings (see also latent heat). The thermal energy can be transported via conduction, convection, radiation or by a combination thereof. The quantity or magnitude of sensible heat is the product of the body's mass, its specific heat capacity and its temperature above a reference temperature. In many cases the reference temperature is inferred from common knowledge, i.e. "room temperature".
latent heat is the amount of energy in the form of heat released or absorbed by a chemical substance during a change of state (i.e. solid, liquid, or gas), or a phase transition.

March 10, 2009  
Anonymous Anonymous said...

Name : Fahrul Rozi
Class: 2.G

Answer Number 10
The British thermal unit (BTU or Btu) is a unit of energy used in the power, steam generation, heating and air conditioning industries. In scientific contexts the BTU has largely been replaced by the SI unit of energy, the joule (J), though it may be used as a measure of agricultural energy production (BTU/kg). It is still used 'unofficially' in metric English-speaking countries (such as Canada, the United Kingdom, and sometimes in New Zealand), and remains the standard unit of classification
One BTU is approximately 1054 – 1060 J

March 10, 2009  
Anonymous Anonymous said...

Name : Ista Fatimah
Class : 2.G
Student's number : 13

Answer Number 14
Exothermic reaction is a reaction that release heat and heat flow from system to surrounding, the enthalpy change must be negative

Endothermic reaction that absorbed heat and heat flow from surrounding to system the enthalpy change must be positive

March 10, 2009  
Anonymous Anonymous said...

Name : Ista Fatimah
Class : 2.G
Student's number : 13

Answer number 5.

q = C.∆T
= 1J/gr °C
= 800J = 0,8kJ

nCH = 130gr / 26gr/mol
= 5 mol

∆H = 1/5mol x 0,8kJ
=0,16kJ

March 10, 2009  
Anonymous Anonymous said...

Name : Ista Fatimah
Class : 2.G
Student's number : 13

Answer number 5.

q = C.∆t
= 1J/gr °C
= 800J = 0,8kJ

nCH = 130gr / 26gr/mol
= 5 mol

∆H = 1/5mol x 0,8kJ
=0,16kJ

March 10, 2009  
Anonymous Anonymous said...

Name : Ista Fatimah
Class : 2.G
Student's number : 13

Answer number 5.

q = C.∆T
= 1J/gr °C
= 800J = 0,8kJ

nC2H2 = 130gr / 26gr/mol
= 5 mol

∆H = 1/5mol x 0,8kJ
=0,16kJ

March 10, 2009  
Anonymous Anonymous said...

1/2 N2 + O2 --> NO2 entalphy change is 33,2 kJ
N2 + O2 --> 2NO2 enthalphy change = 2 x 33,2 kJ
= 66,4 kJ


Name: Rizka Syahputri

March 10, 2009  
Anonymous Anonymous said...

I'm so sorry Ma'am I'm forget the Answer number.
answer number is 18

by Rizka

March 10, 2009  
Anonymous Anonymous said...

class : 2-G
no : 01 (Adies Mariska)

i'm sorry ma'am, i think the answer before is wrong, so this is the correct one.

known.∆Hof CaCO3: -1206.92 kJ/mole
∆Hof CaO : -635.09 kJ/mole
∆Hof CO2 : -393.59 kJ/mole

CaCO3(s) → CaO(s) + CO2(g)

DHO = [DHOf CaO + DHOf CO2] - [DHOfCaCO3]
= [-635.09 + (-393,509)] -[-1206.92]
= (-1028.599) + 1206.92
= +178.321

so, it absorbed heat energy

March 11, 2009  
Anonymous Anonymous said...

Name : Arini Dwi Yulian
Class : 2-G
Absent Number : 5

8)

2XO2 + 2CO → 2XO + 2CO2 ∆H= - 40 kJ
2 XO + 2/3CO2 → 2/3X3O4 + 2/3CO ∆H = - 4 kJ
2/3X3O4 + 1/3CO2→ X2O3 + 1/3CO ∆H = 4 kJ
_________________________________ +

2 XO2 + CO → X2O3 + CO2 ∆H= - 40 kJ


so, ∆H= - 40 kJ

March 11, 2009  
Anonymous Anonymous said...

Name : Ista Fatimah
Class : 2.G
Student number : 13

Answer number 8

2XO2 + 2CO -® 2XO + 2CO2 DH = - 40 kJ
2 XO + 2/3CO2 -® 2/3X3O4 + 2/3CO DH = - 4 kJ
2/3X3O4 + 1/3CO2-® X2O3 + 1/3CO DH = 4 kJ
_________________________________ +

2 XO2 + CO -® X2O3 + CO2 DH = -40 kJ

March 11, 2009  
Anonymous Anonymous said...

name : Dini Yasa Istiqomah
class : 2.G
absent no. : 09

No. 5.

C2H2+5/2 02 -> 2CO2 + H2O DH= 0.16 KJ

Q = c. DT
= 1 J/C. 800 C
= 800 J = 0.8 KJ

n C2H2 = m/Mm
= 130 gr/ 29 gr/mol
= 5 mol

DH = Q/n
= 0.8 KJ/5 mol
= 0,16 KJ

March 11, 2009  
Anonymous Anonymous said...

(18)

KNOWN =

n O2 = 1
n N2 = 2
H = 33.2 kJ/mole


1N2 + 2O2 2NO2
H = 33.2 kJ /mole

QUESTION
H when the reaction was balance?

1N2 + 2O2 2NO2
H1 = 33.2 kJ /mole

= 1/2 N2 + 1O2 NO2


H2 = H1 x mole

H2= 33.2 kJ/mole x 2 mole
H2= 66.4 kJ/mole

March 15, 2009  
Anonymous Anonymous said...

im sorry, im forget to write my name

numb 18

name = desy rachmawati
class= 2.g

March 15, 2009  
Anonymous Anonymous said...

name = desy rachmawati

class= 2.g

numb 17
KNOWN=

NaCl(S) H1= - 411.15kJ (*) H1= + 411.15 KJ
Na(S) + 1/2 Cl2(g) H2= +121.7 KJ
Na(g) + Cl(g) H3= +107.3KJ
Na(g) + Cl(g) H4= +493.3 KJ
Na+(g) + Cl-(g) H5= - 351.2 KJ

(*)because we changed the point is like the other point

ANSWER=

H1 + H2 + H3 + H4 + H5

+ 411.5 kJ + 121,7 kJ + 107.3 kJ + 493.3 kJ – 351.2 kJ

=782.6 kJ

March 15, 2009  
Anonymous Anonymous said...

Name : Randi Syaputra
Class : 2.G
Absent no : 21

Number : 21
= [(2.477)+(3.498,3)]-[(2.805)+(4.465)]
= 2448,9-3486
= 1037,1

March 17, 2009  
Anonymous Anonymous said...

Name : Riezky Pratama Edi Putra
Class : 2.G
Absent no : 22

Number : 22

Question : Enthalpy change for Mg in solid reacts with F2 to create MgF2

1 gr of Mg = 1/24 mole, gives off 46,22 kJ
For 1 mole Mg = 46,22 * 24 = 1109,28 kJ

The answer is 1109,28 kJ

March 17, 2009  
Anonymous Anonymous said...

Name : M. Ridho Rifhansyah
Class : 2.G
Absent : 15
*number 21*

=[(2x477) + (3x498,3] - [(2x1077) + (4x469)]

= 2488,9 kJ/mole - 3486 kJ/mole

= -1037,1 kJ/mol

March 17, 2009  
Blogger fiamfiam said...

nama : fitri amaliah
kelas : xi psia 4
no. absen : 014
guru pembimbing : ibu reni siska

4. 1/2 N2 + 2 H2 + Cr + 2 O2 -> NH4CrO4

∆H = 1806,7 kj/mol

September 01, 2010  
Anonymous Anonymous said...

Nama : maya alvia rahmi
kelas : XI IA 4
no. absen : 022
guru pembimbing : bu reni siska

3. example of thermochemistry applications in daily life:
Many things in the real world are a result of the transfer of heat. From the simple things such as putting ice into your glass of water to the common such as burning fuel for a car, thermochemistry pervades our lives. When one exercises, the body naturally cools down due to sweating. That is because our bodies supply the heat necessary to evaporate the water. Perhaps after exercising, one uses a hot or cold pack. The manufacturing of these little godsends to athletes relies on the endothermic properties of some compounds such as ammonium nitrate to create the cold sensation. Conversely, calcium chloride or magnesium sulfate are compounds that dissolve in water exothermically, releasing that warm, soothing sensation after the blistering cold.

Power plants, from the ranging from the tried and true steam turbines to the dangerous yet high-yield nuclear power plants, all require some method of cooling its machinery. For this task, engineers and chemists once more look towards the fundamentals of thermochemistry for the answer. By utilizing water’s high specific heat capacity, power plants continuously pump water and into their machinery to keep them from overheating. Conveniently, the resulting steam can be collected and reused. This efficient method of cooling machinery has spread to all forms of manufacturing.

September 01, 2010  
Blogger hana tarizkha coganuli said...

nama : Hana Tarizkha Coganuli
kelas : XI PSIA 4
No.absen : 015
guru pembimbing : ibu reni siska

3. contoh penerapan termokimia dalam kehidupan sehari-hari:
A. Ketika kita menyalakan api unggun panasnya akan terasa sampai ke tubuh kita, walaupun kita tidak bersentuhan dengan api unggun. Reaksi ini disebut dengan reaksi eksoterm. Hal ini disebabkan, karena sistem melepas kalor ke lingkungan.

B. Mencairnya es dalam suatu wadah. Reaksi ini disebut dengan reaksi endoterm. hal ini disebabkan karena sistem menyerap kalor dari lingkungan.

September 01, 2010  
Blogger hana tarizkha coganuli said...

Nama : Hana Tarizkha Coganuli
Kelas : XI PSIA 4
No. absen : 015
Guru pembimbing : ibu Reni Siska

3. Contoh penerapan termokimia dalam kehidupan sehari-hari:
A. Ketika kita menyalakan api unggun panasnya akan terasa sampai ke tubuh kita, walaupun kita tidak bersentuhan dengan api unggun. Reaksi ini disebut reaksi eksoterm. Hal ini disebabkan karena sistem melepas kalor ke lingkungan.

B. Mencairnya es dalam wadah. Reaksi ini disebut dengan reaksi endoterm. Hal ini disebabkan karena sistem menyerap kalor dari lingkungan.

September 01, 2010  
Blogger hana tarizkha coganuli said...

nama :

September 01, 2010  
Blogger maya alvia rahmi said...

Nama : maya alvia rahmi
kelas : XI psia 4
no.absen : 022
guru pembimbing : ibu reni siska

3. thermochemistry applications in daily life:

1) Dissolution enthalpies of sugar has a sign (+) (endothermic) so that:
- Dissolving the glass place feels a bit cold (use sugar that much to watch this)
- Hot water dissolves the sugar much faster

compare this with the dissolution of salt that is not endothermic

2) Water has a heat capacity does not go far so fast is not fast heat and cold, this led to, for example:
- The phenomenon of land breeze and sea breeze
- The use of ice in an ice bucket effectively keep the temperature stays low for a prolonged period
- Etc.

3) exothermic reacting compounds widely used as a fuel, eg LPG, gasoline, gas oil, etc.

September 01, 2010  
Blogger andhinata said...

nama : Andhina Riskyta Putri
kelas : XI PSIA 4
no. absen : 05
guru pembimbing : Reni Siska

answer no. 9 :
LATENT HEAT is the amount of energy released or absorbed by a chemical substance during a change of state that occurs without changing its temperature, meaning a phase transition , like the melting of ice or the boiling of water.

The specific latent heat is the amount of energy required to convert 1 kg (or 1 lb) of a substance from solid to liquid (or vice-versa) without a change in the temperature of the surroundings – all absorbed energy goes into the phase change – is known as the specific latent heat of fusion.

The formula is :
Q = mL

where:

Q = is the amount of energy released or absorbed during the change of phase of the substance (in kJ or in BTU),
m = is the mass of the substance (in kg or in lb), and
L = is the specific latent heat for a particular substance (kJ-kgm−1 or in BTU-lbm−1); substituted as Lf to represent as the specific latent heat of fusion, Lv as specific latent heat of vaporization.

In other words, specific latent heat is found when energy is divided by mass, or as represented as L = Q / m


SENSIBLE HEAT is the amount of energy released or absorbed by a chemical substance during a change of temperature.

The formula is :
Q sensible = m.c.ΔT

where
m = is the mass of the body,
c = is the specific heat capacity of that body at the appropriate temperature and pressure range, and
ΔT = is the change in temperature of the body.

September 01, 2010  
Blogger andhinata said...

nama : Andhina Riskyta Putri
kelas : XI PSIA 4
no. absen : 05
guru pembimbing : Reni Siska

answer no. 9 :
LATENT HEAT is the amount of energy released or absorbed by a chemical substance during a change of state that occurs without changing its temperature, meaning a phase transition , like the melting of ice or the boiling of water.

The specific latent heat is the amount of energy required to convert 1 kg (or 1 lb) of a substance from solid to liquid (or vice-versa) without a change in the temperature of the surroundings – all absorbed energy goes into the phase change – is known as the specific latent heat of fusion.

The formula is :
Q = mL

where:

Q = is the amount of energy released or absorbed during the change of phase of the substance (in kJ or in BTU),
m = is the mass of the substance (in kg or in lb), and
L = is the specific latent heat for a particular substance (kJ-kgm−1 or in BTU-lbm−1); substituted as Lf to represent as the specific latent heat of fusion, Lv as specific latent heat of vaporization.

In other words, specific latent heat is found when energy is divided by mass, or as represented as L = Q / m


SENSIBLE HEAT is the amount of energy released or absorbed by a chemical substance during a change of temperature.

The formula is :
Q sensible = m.c.ΔT

where
m = is the mass of the body,
c = is the specific heat capacity of that body at the appropriate temperature and pressure range, and
ΔT = is the change in temperature of the body.

September 01, 2010  
Anonymous Anonymous said...

name : Tarisha Raddin Wulan Putri
class : XI PSIA 4
absent number : 031
teacher : Mrs. Reni Siska
two examples of thermochemistry are:
- boiling a kettle to make a cup of tea
- the phenomenon of surface winds and sea breezes

September 01, 2010  
Blogger Almira Larmen said...

Name : Almira Dina Mariski
Class : XI.PSIA4
Absent : 02

14. exothermic reaction is a reaction that emits energy or generate energy when the reaction occurs. usually, this reaction produces heat.
Examples:
- Burning kerosene oil stove

endothermic reaction is a reaction that requires energy or absorb energy from the environment when a reaction occurs. This reaction usually produces cold temperatures.
Examples:
- Assimilation
- Photosynthesis

September 01, 2010  
Blogger tiya amalia enira said...

said ..
nama : Tiya Amalia Enira
Kelas : XI.PSIA 4
No. Absen : 032
guru pembimbing : ibu reni siska

1. Thermochemistry is the study of the energy evolved or absorbed in chemical reactions and any physical transformations, such as melting and boiling. Thermochemistry, generally, is concerned with the energy exchange accompanying transformations, such as mixing, phase transitions, chemical reactions, and including calculations of such quantities as the heat capacity, heat of combustion, heat of formation, enthalpy, and free energy.

September 01, 2010  
Blogger tiya amalia enira said...

said ..

nama : Tiya amalia enira
kelas : XI.PSIA 4
no. absen : 032
guru pembimbing : ibu reni siska

2. 2 examples of thermochemistry applications in daily life :

a. All of the combustion reaction
b. Process of photosynthesis

September 01, 2010  
Anonymous Anonymous said...

name : citra indah sari
class : XI PSIA 4
absent : 09

no. 14
What are differences between an exothermic reaction and an endothermic reaction?

exothermic reaction is a chemical reaction that release heat energy to the surrounding. Exothermic reaction has a negative ∆H.
Example : All combustion reactions

endothermic reaction is a chemical reaction that absorbs heat from surrounding to system. Endothermic reaction has a positive ∆H.
Example : melting ice

September 01, 2010  
Blogger Septami Putri said...

nama : Septami Putri Hajati
kelas : XI PSIA 4
guru :ibu Reni Siska

nomor 14
Endothermic reaction :
is a reaction that absorp energy. It means that when the reaction happen, the reaction will be absorp an energy from environment to the system. Because of that, the entalphi change (∆H) positive (+). Endothermic reaction : ∆H = Hp – HR > 0 (positive)
Examples : - Photosynthesis (In this process, plants use the energy from the sun to convert carbon dioxide and water into glucose and oxygen)

Exothermic reaction :
is a reaction that release energy. It means that when the reaction happen, the reaction will be release energy from system to the enviromennt and it makes the heat lost. Because the heat is lost, the entalphi change (∆H) will be negative (-).
Exothermic reaction : ∆H = HP – HR < 0 (negative)
Examples : - when we put a glass of hot water into a bowl of cold water (the heat from a glass of hot water (system) will lost and remove to a bowl of cold water (environment).

September 01, 2010  
Blogger shella nurrakhmaniar said...

nama: shella nurrakhmaniar
kelas: xi psia 4
no absen: 029
guru pembimbing: reni siska hartati, s.pd

2. Many things in the real world are a result of the transfer of heat. From the simple things such as putting ice into your glass of water to the common such as burning fuel for a car, thermochemistry pervades our lives. When one exercises, the body naturally cools down due to sweating. That is because our bodies supply the heat necessary to evaporate the water. Perhaps after exercising, one uses a hot or cold pack. The manufacturing of these little godsends to athletes relies on the endothermic properties of some compounds such as ammonium nitrate to create the cold sensation. Conversely, calcium chloride or magnesium sulfate are compounds that dissolve in water exothermically, releasing that warm, soothing sensation after the blistering cold.

Power plants, from the ranging from the tried and true steam turbines to the dangerous yet high-yield nuclear power plants, all require some method of cooling its machinery. For this task, engineers and chemists once more look towards the fundamentals of thermochemistry for the answer. By utilizing water’s high specific heat capacity, power plants continuously pump water and into their machinery to keep them from overheating. Conveniently, the resulting steam can be collected and reused. This efficient method of cooling machinery has spread to all forms of manufacturing.

September 02, 2010  
Anonymous Anonymous said...

Wardah Amalia_XI PSIA 4
Guru pembimbing: ibu Reni
1.thermochemistry is the study of the heat envolved or absorbed in chemical reactions. It is concerned with the heat exchange accompany transformations, such as mixing, phase transitions, chemical reactions, which includes calculations of such quantities as the heat capacity, heat of combustion, heat of formation,etc.

September 02, 2010  
Blogger karinagatri said...

nama : Karina Gatri Aliva
kelas : XI PSIA $
no.absen : 12
guru pembimbing : ibu Reni Siska

no.14

Endothermic reaction / Endotermal

Endothermic reaction is a reaction that requires energy or absorb energy from the environment when a reaction occurs. This reaction generally produces cold temperatures.

Examples of endothermic:
- Assimilation
- Photosynthesis

In endothermic reactions, energy absorbing system. Therefore, the enthalpy of the system will increase. This means that the product enthalpy (Hp) is larger than the reactant enthalpy (Hr). Consequently, changes in enthalpy, an enthalpy difference between enthalpy of products with reagents (Hp-Hr) marked positive. So that changes in enthalpy for the endothermic reaction can be stated:

ΔH = Hp-Hr> 0 (13)


Exothermic reaction / Eksotermal

Exothermic reaction is a reaction that emits energy or generate energy when the reaction occurs. Generally, this reaction produces heat.

Examples of endothermic:
- Burning kerosene oil stove
- The flame of a campfire while camping
In contrast, the exothermic reaction, liberate energy system, so the enthalpy of the system will decrease, meaning that the product is smaller than the enthalpy of reaction enthalpy. Therefore, changes entalpinya marked negative. So that p can be expressed as follows:

Hp-Hr = ΔH <0 (14)

September 02, 2010  
Blogger siti nurul badriyah said...

name: Siti Nurul Badriyah
class: xi psia 4
absent: 30
teacher: ibu reni

1. thermochemistry is the study of the energy evolved or absorbed in chemical reactions and any physical transformations, such as melting and boiling.

September 03, 2010  
Blogger qopa almaisurie said...

name: qopa almaisurie
class: xi psia 4
absen number: 025
teacher: ibu reni siska

number 14
Exothermic reaction is a reaction that release calor. The calor flow/move from system to environment.
∆H = Hp – HR < 0
Example: all of the combustion process

Exothermic reaction is a reaction that release calor.
The calor flow/move from system to environment.
∆H = Hp – HR < 0
Example: all of the combustion process

Exothermic reaction is a reaction that release calor.
The calor flow/move from system to environment.
∆H = Hp – HR < 0
Example: all of the combustion process

Endothermic reaction is a reaction that absorb calor.The calor flow/move from environment to system.
∆H = Hp – HR > 0
Example: ice making

September 03, 2010  
Blogger putri suci said...

name : putri suci mawariza
class: xi psia 4
number: 024
teacher : ibu reni siska

14. what are differences between an exothermic and endothermic reaction?

answer:
exothermic reaction :
- heat flow : from system to environment
- environment temperature: increased
- ?H = -
- Hp < Hr

endothermic reaction :
- heat flow : from environment to system
- environment temperature : down
- ?H = +
- Hp > Hr

Hp : entalpi produk
Hr : entalpi reaktan

September 04, 2010  
Blogger putri suci said...

name : putri suci mawariza
class: xi psia 4
number: 024
teacher : ibu reni siska

14. what are differences between an exothermic and endothermic reaction?

answer:
exothermic reaction :
- heat flow : from system to environment
- environment temperature: increased
- ?H = -
- Hp < Hr

endothermic reaction :
- heat flow : from environment to system
- environment temperature : down
- ?H = +
- Hp > Hr

Hp : entalpi produk
Hr : entalpi reaktan

September 04, 2010  
Anonymous bagaswara ramadhan said...

nama : bagaswara ramadhan
kelas : XI PSIA 4
no absen : 6
guru pembimbing : ibu reni siska

8.2XO2 + 2CO -> 2XO + 2CO2 ∆H = -20 X 2 ∆H = -40 kJ
2XO + 2/3 CO2 -> 2/3X3O4 + 2/3 CO ∆H = 2/3 X 6 ∆H = -4 kJ
2/3X3O4 + 1/3CO2 -> X2O3 + 2/3 CO ∆H = 12 : 3 ∆H = 4kJ
_________________________________ +

2XO2 + 2CO -> X2O3 + CO2 ∆H = -40 kJ

the answer is -40kj

September 05, 2010  
Blogger aditia pato said...

for question number 1
name: aditia Kurniawan
Class: XI PSIA 4
Absen: 001
teacher: Mrs. Reni Siska
ehm..
thermochemistry is the study of the energy evolved or absorbed in chemical reactions and any physical transformations, such as melting and boiling. Thermochemistry, generally, is concerned with the energy exchange accompanying transformations, such as mixing, phase transitions, chemical reactions, and including calculations of such quantities as the heat capacity, heat of combustion, heat of formation, enthalpy, and free energy.

September 05, 2010  
Anonymous Anonymous said...

Name: Elzan Zulqad Maulana
Class: XI IA 4
Absent: 012
Teacher: Ma'am Reni Siska Hertati

11. Hess's law states that the enthalpy change for a reaction depends on the products and reactants and is independent of the pathway or the number of steps between reactants and products. In other words, if a reaction is carried out in a series of steps, ΔH for the reaction will be equal to the sum of the enthalpy changes for the individual steps.

For example consider the exothermic reaction between sulfur and oxygen to produce sulfur dioxide, followed by the exothermic reaction between sulfur dioxide and more oxygen to produce sulfur trioxide, as the following reaction:
S(s) + O2(g)-->SO2(g) ∆H= -296.83 kJ
SO2(g) + ½O2(g)-->SO3(g) ∆H= -98.9 kJ

If these two steps are concluded as a simple one step of overall reaction, then the heat evolved/absorbed is the sum of the two steps:
S(s) + 1½O2(g)-->SO3(g)∆H= -395.57 kJ

September 05, 2010  
Blogger tiya amalia enira said...

said...

nama : Tiya Amalia Enira
kelas : xi psia 4
no. absen : 032
guru pembimbing : ibu reni siska

3. 2 examples of thermochemistry applications in daily life :
- Process of Photosynthesis
- all of the combustion reaction

September 05, 2010  
Blogger tiya amalia enira said...

said...

nama : Tiya Amalia Enira
kelas : xi psia 4
no. absen : 032
guru pembimbing : ibu reni siska

3. 2 examples of thermochemistry applications in daily life :
- Process of Photosynthesis
- all of the combustion reaction

September 05, 2010  
Anonymous M.Ardhy Zulyo said...

Nama :M.Ardhy Zulyo
kelas:xi psia 4
no.absen: 019
guru pembimbing: ibu reni siska

Endothermic reaction that absorbed heat and heat flow from surrounding to system the enthalpy change must be positive

Exothermic reaction is a reaction that release heat and heat flow from system to surrounding, the enthalpy change must be negative

September 06, 2010  
Anonymous Anonymous said...

nama

September 06, 2010  
Blogger M. Rasyid Ridha said...

Name : M. Rasyid Ridha
Class : XI PSIA 4 2010/2011
Absent no. : 18
Teacher : Ibu Reni Siska Hertati
No. 1
1. Thermochemistry is the study of the energy evolved or absorbed in chemical reactions and any physical transformations, such as melting and boiling. (www.wikipedia.org)
my blog:www.edo-undercover.blogspot.com

September 06, 2010  
Blogger marisa said...

nama : marisa triyanti
kelas : xi psia 4
no.absen : 20
guru pembimbing : ibu reni siska
no.soal : 9

9. Sensible heat is the heat absorbed or given off by a substance that is not in the process of changing its physical state.

Latent heat is the heat absorbed or given off by a substance while it is changing its physical state.

September 06, 2010  
Blogger marisa said...

nama : marisa triyanti
kelas : xi psia 4
no. absen : 20
guru pembimbing : ibu reni siska

10. A British Thermal Unit (BTU) is the amount of heat energy needed to raise the temperature of one pound of water by one degree F. This is the standard measurement used to state the amount of energy that a fuel has as well as the amount of output of any heat generating device.

September 06, 2010  
Blogger khalil ar said...

nama : khalil al rahman
kelas : xi psia 4
no. absen : 017
guru pembimbing : Ibu reni siska

9.Sensible heat
When an object is heated, its temperature rises as heat is added. The increase in heat is called sensible heat. Similarly, when heat is removed from an object and its temperature falls, the heat removed is also called sensible heat. Heat that causes a change in temperature in an object is called sensible heat.

Latent heat
All pure substances in nature are able to change their state. Solids can become liquids (ice to water) and liquids can become gases (water to vapor) but changes such as these require the addition or removal of heat. The heat that causes these changes is called latent heat. or we can say that latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase (e. solid, liquid, or gas), – also called a phase transition

September 08, 2010  
Blogger hana tarizkha coganuli said...

name : Hana Tarizkha Coganuli
class : XI PSIA 4
absent : 15
teacher : ibu Reni Siska

9. SENSIBLE HEAT is the amount of energy released or the heat absorbed or given off by a substance that is not in the process of changing its physical state. Sensible heat can be sensed or measured with a thermometer, and the addition or removal of sensible heat will always cause a change in the temperature of the substance. Sensible heat is that caused by conduction and convection.

LATENT HEAT is the heat absorbed or given off by a substance while it is changing its physical state. And the heat which flows to or from a material without a change to temperature. Such as the condensation of water vapour. Latent heat is the heat moved by evaporating and condensing

September 14, 2010  
Blogger fadel muhammad said...

name : fadel muhammad
class : XI PSIA 4
teacher : Mrs Reni

no.13
How do we measure the enthalpy of a reaction? Explain your answer sharply.

answer :
to determine the enthalpy of a single reaction, we can combine some reactions as a way to determine the single reaction enthalpy. The final result that we will receive will show the same value.

For example:

Enthalpy of formation of NO2 can we find the following reactions:

N2 (g) + O2 (g) -> 2NO2 (g) deltaH = 68 KJ

September 15, 2010  
Anonymous banissalam said...

name: banissalam
class : XI PSIA 4
teacher : Mrs.Reni Siska Hartati

19)for standard enthalpy of reaction, all reactants and product are measured in standard condition where the pressure temperature and also the number of mole are all standard. so, the different values of enthalpy reaction could happen because they are not measured in same condition. that's why the reaction only have one value for standard enthalpy reaction.

September 19, 2010  
Blogger beelzebub's blog said...

name: bryan chandra
class: XI PSIA 5
Teacher : Mrs. Septaria
3) Give 2 examples of thermochemistry applications in daily life.
•If we burn on the canddle, we feel hot if we put our hand behind the fire(ecxothermic reaction)
•In the refrigerator, if we put our hand in beside the refrigerator, we can feel hot in there(ecxothermic reaction)
•If we make a hot milk, we can feel hot if we touch the glass( ecxothermic reaction)
14) What are differences between an exothermic reaction and an endothermic reaction?
•Exothermic reaction: reaction which release the heat to environment
•Endhothermic reaction: reaction that absorbs heat from environment
15) If a reaction can not go spontaneously what you will do? Explain your answer by giving an example of each way.
We can increase the heat so maybe the reaction can do spontaneously
We do the reaction with gradual reaction(hess law,maybe)
Example: spontan reaction: C + O2 = CO2
Graduail reaction:C + ½O2 = CO
CO + ½ O2 = CO2

September 19, 2010  
Anonymous Anonymous said...

Nama : Ratri Ayu Shintya
Kelas : XI PSIA 4
Guru Pembimbing : Bu Reni .


THE DIFFERENCES BETWEEN EXOTHERMIC AND ENDOTHERMIC

ENDOTHERMIC PROPERTIES EXPLAINED

* Energy is drawn in from the external environment, causing its surroundings to loose heat, or "cool down."

* The endothermic chemical reaction creates a product that has a higher energy level than the original materials, causing the reactant's stored energy to decrease. (In scientific terms, the reactants have "less total enthalpy" than the product.)

* The resulting product of the reaction is less stable because, the higher the energy bond, the less strength its molecules possess.

* Most endothermic reactions are not spontaneous.

example :Melting ice. In order for ice to melt, it needs to draw in the heat (energy) from its surroundings. The ice becomes less stable as it responds to the increased heat. The ice's stored energy decreases. The end product is water, which has a higher energy level than the ice.

EXOTHERMIC PROPERTIES EXPLAINED

* Exothermic chemical reactions cause their surroundings to warm up by giving off heat.

* The reactants contain more stored energy than the product because energy from external sources is not required, but given off. This gives the product more stability due to the lower amount of energy needed. (In this case, the reactants have a "greater total enthalpy" than the product.)

* Exothermic reactions are usually spontaneous.

example :Lighting a match. When the head of the match is struck, it results in the spontaneous release of stored energy (heat) from the reactants into the surroundings. The flame that is produced has a lower level of energy than the match and the striking surface because the reaction is giving off stored energy and not required to draw energy in from its surroundings.

September 19, 2010  
Blogger Amellia Sefti said...

Nama : Amellia Sefti Lestari
Kelas : XI PSIA 4
Guru : Bu Reni
Answer : No. 8

2XO2 + 2CO -® 2XO + 2CO2 DH=-40KJ
2/3 X3O4 + 1/3 CO2 -® X2O3 + 1/3 CO DH=+4KJ
2XO + 2/3 CO2 -®2/3 X3O4 + 2/3 CO DH=-4KJ
_____________________________________________+
2XO2 + CO -®X203 + CO2 DH = -40 KJ

September 19, 2010  
Blogger irham's page said...

Nama: Maulana Jailani Irham
Kelas: XII PSIA 4
Guru: Bu Reni
Answer: no. 14

Endothermic reaaction : An endothermic reaction need energy or absorp an energy from environment to a system when the reaction happen.This reaction may absorp heat and the themperature of the system will increase.so,the entalphi change(∆H) will be possitive (+)
For example: when we boil water in a teapot , it will receive heat energy from the invironment.and it's themperature will increase.

Exothermic reaction : An exothermic reaction release energy from system to an environment when the reaction happen.This reaction may miss heat energy because it remove it's own energy to the environment.so,the entalphy change(∆H) will be negative (-)

For example : When we put A glass of hot water in a room themperature.it's heat will remove to the environment.and it will lost energy.so,it's themperature will decrease.

September 20, 2010  
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March 31, 2013  
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June 07, 2013  
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June 11, 2013  

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