Stoichiometry

Predicting amounts of reagents needed or amounts of products

made

2 C2H6 + 7 O2 4 CO2 + 6 H2O

How much CO2 will be produced if 4 moles of C2H6 are consumed?

Stoichiometry problems:1) Start with balanced chemical equation

2) Problem will ask how many moles/liters given yield certain amount of something else

2 C2 C22HH66 + 7 O2 4 CO4 CO22 + 6 H2O

How much COCO22 will be produced if 4 moles of CC22HH66 are consumed?

4 X

___________ ___________4 moles C2H6

2 moles C2H6

=X moles CO2

4 moles CO2

X = 8 moles CO2

2 C2 C22HH66 + 7 O2 4 CO2 + 6 H6 H22OO

How much HH22OO will be produced in the combustion of 5 moles of CC22HH66?

5 X

5 moles C2H6____________

2 moles C2H6

= X moles H2O___________

6 moles H2O

X = 15 moles H2O

2 C2 C22HH66 + 7 O7 O22 4 CO2 + 6 H2O

How much oxygenoxygen will react with 5 moles of CC22HH66?

5 X

5 moles C2H6___________

2 moles C2H6

= X moles O2___________

7 moles O2

X = 17.5 moles O2

Coefficients in Balanced Equations

• Give relative number of particles in rxn

• Give relative number of moles in rxn

• Coefficients: mole ratios of each component

• use these relationships in MOLE-MOLE problems to convert from moles of 1 substance to moles of another substance

Volume/Volume Word Problems Involving Gases

Gas-Phase Equations

• 1 mole any gas occupies same volume as any other gas (At STP = 22.4 L/mol)

• In reactions where ALL reactants & products are gases:

coefficients represent ratio of volumes of gases

15 xN2(g) + 3 H2(g) 2 NH3(g)

How much hydrogen gas will react with 15 liters of nitrogen gas?

15 L N2(g)_________

1 L N2(g)= X L H2(g)_________

3 L H2(g)

X = 45 L H2(g)