# STOICHIOMETRY

## What is Stoichiomtry?

I know this is a funny word to pronounce, so let me help you out with that first, [STOY-KEE-AHM-EH-TREE]. Trust me, the concept is simple once you know what it is. Stoichiometry is the part of chemistry that studies the amount of substances that are involved in the reactions. Stoichiometry is all about the numbers. All the reactions in a balanced equation are dependent on how much stuff you have. This helps with how much you started with or need. This involves: mole to mole conversions, mass to mass conversions, molar mass, the limiting or excess reactants, and theoretical and percent yields.

## How to solve Stoichiomtry problems:

For Mass to Mass problems:

1. Write a balanced equation for the reaction.

2. Write the given mass on a factor-label form.

3. Convert mass of reactant to moles of reactant.

4. Convert moles of reactant to moles of product.

5. Convert moles of product to grams of product.

6. Pick up the calculator and do the math to get the answer.

For mole to mole problems:

1. Write a balanced equation.(requires a mole ratio)

2. Use the coefficients from the equation and multiply it by appropriate mole ratio

3. Pick up the calculator and do the math to get the answer.

EX. (mass to mass) Lead(II) Nitrate and Sodium Bromide

1. Pb(NO₃)₂ +2NaBr → PbBr₂ + 2Na(NO₃)₂

2. 331.2 g.- Pb(NO₃)₂ 369 g.- PbBr₂ 102.9 g.- NaBr 85 g.- Na(NO₃)₂

3. Use dimensional analysis to get the answer and easier.

4. 6.2 grams

## Research of my chemical equation: aluminum and silver sulfide: 2Al + 3Ag2S >> 6Ag + Al2S3

When silver tarnishes, it combines with sulfur and forms silver sulfide. Silver sulfide is the color of black. To clean tarnished silver is to reverse the chemical equation and have silver sulfide react with aluminum metal. Aluminum is an oxidizing agent and the silver in silver sulfide is reduced back to silver metal.