### Let's Try to Learn Stoichiometry

As I've been teaching in a senior high school with plus curriculum for about 11 years, I'm experienced enough to know what kinda chemistry problems for Indonesian students. I hope they may find some solutions for their chemistry problems here. This post will explain the stoichiometry concept only because it's commonly the hardest part of chemistry for Indonesian students but it will relate with many parts of chemistry and it's the basic of chemistry calculations.

What's the basic of Stoichiometry?

The basic concept is mathematics. Once you understand math well you can learn stoichiometry easier for sure.

To make this field being narrower, here are the equations you need to get closer with.

General equations

Molar mass of an atom is equal to the molecular weight of the given atom.

Molar mass of a molecule is equal to the molecular weight of the given molecule.

- mass = the number of moles x molar mass

- the number of molecules = the number of moles X Avogadro number

- the number of moles = Molarity x Volume

For specific conditions

- At standard temperature and pressure

V = n . Vm

V = n x 22.4 liter/moles

- At specific temperature and pressure

where P = pressure (atm)

n = the number of moles

R = the ideal gas constant (0.082 liter.atm/mol.K)

V1 . n2 = V2 . n1

where V1 and V2 = volume of gases

n1 and n2 = the number of moles of gases

What are steps to solve a stoichiometry problem?

Here are the steps and do them in the manner:

- Read and understand the problem and list the known stuffs. Don't mention the earlier word of a given number but the later one of the given number.

What is the number of mass of 2.24 liters of ammonia....

So the known stuff is 'volume of ammonia or V' not 'the mass of ammonia or m'

- Determine if the problem needed a chemical equation or not. Write a balanced chemical equation if it needed it.

Go to the next point if it didn't.

heated.

In this case, you need to write a chemical equation and then balance it. Just use a balanced

equation to solve any chemistry problems.

- List the equation(s) which you need to solve by using the known stuffs. Circle the known numbers and leave the unknown ones. Solve equations as many as possible.

- Add the new known number(s) into the equation(s) which you must solve.
- Convert the equation into the asked stuff in the problem and run it.
- You just solve a chemistry problem!

Labels: Chemistry, Stoichiometry

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