reacting masses(40 points)

1. Gas masks used by fire fighters often contain potassium superoxide (KO2). Potassium superoxide reacts with carbon dioxide and water in the exhaled breath to produce oxygen by the following reaction:
4KO2 + 2H2O + 4CO2 → 4KHCO3 + 3O2
Assume that a person exhaled 14.0 g of carbon dioxide over 20 minutes.
a) Calculate the minimum mass of potassium superoxide the mask should contain in order to react with all the carbon dioxide.
b) Suppose the process was only 80% efficient. What would be the mass of potassium superoxide needed?
(Relative atomic masses: C = 2.0, O=16.0, K = 39.1)


(a)
4KO2 + 2H2O + 4CO2 → 4KHCO3 + 3O2
Mole ratio KO2 : CO2 = 4 : 4 = 1 : 1

Mole mass of CO2 = 12 + 16x2 = 44 g /mol
No. of moles of CO2 = 14/44 mol
Minimum no. of moles of KO2 needed = 14/44 mol
Molar mass of KO2 needed = 39.1 + 16x2 = 71.1
Minimum mass of KO2 needed = (14/44) x 71.1 = 22.6 g

(b)
Efficiency = 80%
Mass of KO2­ needed = 22.6/80% = 28.3 g