Reaction Stoichiometry

Weight relations in chemical reactions:1.If I react this much, how much product do I get?2.If I need this much product, how much do I need to react

1. If you have 200 tires, how many cars can you make?

1. 200 2. 100 3. 800 4. 50

2. If you have 200 tires, how many motorcycles can you make?

1. 200 2. 100 3. 800 4. 50

3. Consider:

Pb(NO3)2(aq) + 2 NaCl(aq) --> PbCl2(s) + 2 NaNO3(aq) If you have 5 moles of Pb(NO3)2, how many moles of PbCl2 can you make? 1. 5 2. 10 3. 2.5 4. Consider:

Pb(NO3)2(aq) + 2 NaCl(aq) --> PbCl2(s) + 2 NaNO3(aq) If you have 5 moles of NaCl, how many moles of PbCl2 can you make? 1. 5 2. 10 3. 2.5

How to Balance Equations

• One element at a time• Trial and error

Al + Br2 Al2Br6

CH3CH2OH + O2 CO2 + H2O

CH3OH + O2 CO2 + H2O

General Stoichiometry RouteGrams reactant

Molesreactant

Moles product

Gramsproduct

2 CH3OH + 3 O2 2 CO2 + 4 H2OIf we react 100 grams of CH3OH, how many grams of H2O are formed?

amounts table

2 H2O2 O2 + 2 H2OIf we react 12 grams of 30% H2O2, how many grams of O2 are formed?

Limiting Reactants

1. If you have 200 tires and 75 steering wheels, how many cars can you make?

1. 2002. 753. 504. 100

Example 2.

A cake recipe calls for 3 eggs, 2 cups of flour, and 3 teaspoons of sugar. If you have:

• 9 eggs• 8 cups of flour• 12 teaspoons of sugar

how many cakes can you make? Enter the number of cakes.

Example 3.

Which reaction is correct?

2 CO(g) + O2(g) 2 CO2(g)

A hard OWL Question:

actual experimental yield% Yield = 100%

theoretical calculated yield

Alum Lab Calculations:Let’s say you start with 0.985 g Al and make 14.8 g KAl(SO4)212 H2O product.

What is the percent yield?

Molar masses: Al = 26.98; KAl(SO4)212 H2O = 474.37 g/mol

Chemical Analysis

Chemical Analysis: Determining Formulas