Stoichiometry

Element Measure

2 H2 + O2 2 H2O

2 molecules of hydrogen react with every molecule of oxygen to produce 2 molecules of water

2 moles of hydrogen react with every mole of oxygen to produce 2 moles of water

2 H2 + O2 2 H2O

Multiply by 24 H2 + 2 O2 4 H2O

4 moles of hydrogen react with every 2 moles of oxygen to produce 4 moles of water

Divide by 2 H2 + 0.5 O2 H2O

1 mole of hydrogen reacts with every 0.5 moles of oxygen to produce 1 mole of water

Pancake comparison

250 mL of pancake batter + 500 mL milk

6

How much pancake batter do I need if I only want to make 2 pancakes?

2 H2 + O2 2 H2O

How many moles of H2 are required to produce 4 moles of H2O?

How many moles of O2 are required?4 = 2xx = 4/2

x = 2 moles O2

2 H2 + O2 2 H2O

How many moles of O2 are required to produce 0.5 moles of H2O?

0.25 moles of O2

2 H2 + O2 2 H2O

How many moles of O2 are required to produce 7 moles of H2O?

3.5 moles of O2

2 H2 + O2 2 H2O

What mass of O2 and H2 are required to produce 9 moles of H2O?

n = mMM

m

MMn144 g of O2

2 H2 + O2 2 H2O

What mass of O2 and H2 are required to produce 9 moles of H2O?

2 1 2

94.5

18.18 g of H2

2 H2 + O2 2 H2O

What mass of H20 is present when 9 moles are produced?

2 1 2

99 4.5

162.18 g of H2O

2 H2 + O2 2 H2O

4 g of H2 react with what mass of O2 in the above reaction?

2 H2 + O2 2 H2O

4 g of H2 react with what mass of O2 in the above reaction?

2 1 2

31.68 g of O2

C3H8 + 5 O2 3 CO2 + 4 H2O

220 g of C3H8 react in the above reaction. What mass of H2O is produced?

C3H8 + 5 O2 3 CO2 + 4 H2O

220 g of C3H8 react in the above reaction. What mass of H2O is produced?

1 5 3 4

Pb(NO3)2 + 2 NaI PbI2 + 2 NaNO3

50 mL of a 0.5 mol/L solution of NaI reacts to produce how many grams of PbI2?

C = nV

Pb(NO3)2 + 2 NaI PbI2 + 2 NaNO3

50 mL of a 0.5 mol/L solution of NaI reacts to produce how many grams of PbI2?

1 2 1 2

Stoichiometry Steps

1. Write and balance the equation2. Write the ratio of substances in moles on top of the

equation3. Convert the given information into moles

(if necessary)4. Complete a cross-multiplication to determine the

number of moles of the substance in question5. Convert the answer into the required units (e.g.

grams)6. Write out the answer to the question in correct units.