Problem 9.124 Ozone (O3) can be prepared in the laboratory by passing an electri

Question

Problem 9.124 Ozone (O3) can be prepared in the laboratory by passing an electrical discharge through oxygen gas: 3O2(g)2O3(g). Assume that an evacuated steel vessel with a volume of 10.0 L is filled with 32.55 atm of O2 at 25 C and an electric discharge is passed through the vessel, causing some of the oxygen to be converted into ozone. As a result, the pressure inside the vessel drops to 28.65 atm at 25.0 C. Part A What is the final mass percent of ozone in the vessel? mass percent of O3 = mass % SubmitMy AnswersGive Up

Explanation / Answer

V = 10 L

P = 32.55 atm of O2 T = 298K

PV = nRT

n = PV/(RT) = 32.55*10/(0.082*298) = 13.3205 mol

3O2 = 2O3

P final = 28.65 atm

initially

P-O2 = 32.55

P-O3 = 0

the reaction extent

P-O2 = 32.55 - 3x

P-O3 = 0 +2x

Ptotal = PO2 + PO3 = 32.55 - 3x + 0 +2x = 28.65

32.55 -x = 28.65

x = 32.55 -28.65 = 3.9

now

P-O2 = 32.55 - 3*3.9 = 20.85 atm

P-O3 = 0 +2*3.9 = 7.8 atm

find % of O3 in vessel -->

mol of O2 = 13.3205 * 20.85 /28.65 = 9.6939 mol of O2

mol of O3 = 13.3205 * 7.8 /28.65 = 3.6265 mol of O3

mass of O2 = 9.6939 *32 = 310.2048 g

mass ofO3 = 3.6265 *48 = 174.072 g

% O3 = mass of O3 / total mass * 100% = 174.072/(310.2048 +174.072 ) *100 = 35.94473 % is O3

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