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InterviewSolution
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7. Considering air as a 4 1 mixture of nitrogen andoxygen, the mass ofar in a hall with dimensions 5m Ă5m Ă 5m at STP is approximately(A) 160 g(C) 160 kg(B) 16g(D) 1.60 kg |
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Answer» PV = nRT n = m/M (mass/molarmass) PV = mRT/M PM/RT = m/V = D The effective molar mass of air is 0.8x28 + 0.2x32 = 22.4 + 6.4 = 28.8g/mole. so D = 1atm x 28.8g/mole / (0.0821Latm/moleK x 301K) = 1.17g/L Another way to think about it is: At STP the density of air is 28.8g/22.4L = 1.29g/L Gases expand when heated so the density will decrease if T increases from 273 to 301 so applying a temperature correction factor: 1.29g/L x 273/301 = 1.17g/L |
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