Chapter 19

Gas Stoichiometry

If an excess of chlorine gas reacts with a solution containing 20.0g of potassium bromide how many

cm3 of bromine gas can be produced at STP?

2KBr + Cl2 → Br2 + 2KCl

20.0g KBr

119g KBr

mol KBr

2 mol KBr

1 mol Br2

1 mol Br2

22.4 dm3

1 dm3

1000 cm3

= 1880 cm3

In the reaction between aluminum and oxygen, how many grams of aluminum are needed to react with

5.00 dm3 of oxygen at STP?

4Al + 3O2 → 2Al2O3

5.00 dm3 O2

22.4 dm3

mol O2

3 mol O2

4 mol Al

mol Al

27.0 g= 8.04 g

How many cm3 of chlorine gas are required to react with hydrogen gas to produce 50.0 cm3 of hydrogen chloride gas at STP?

H2 + Cl2 → 2HCl

• This is a volume – volume calculation.• We can use a shortcut for these type of calculations.

50.0cm3 HCl

2 cm3 HCl

1 cm3 Cl2

= 25.0 cm3

Homework

• Worksheet: Gas Stoichiometry

• Lab Summary: “Molecular Mass of a Gas”