A plot of the density versus the pressure for air at 27°C has the limiting slope = 1.2 × 10^-5 kg m^-3 Pa^-1. The composition of air (contains only and ) in volume ratio of and is (R = 8.0 J/K-mol)

Question

A plot of the density versus the pressure for air at 27°C has the limiting slope = 1.2 × 10^-5 kg m^-3 Pa^-1. The composition of air (contains only $N_2$ and $O_2$) in volume ratio of $N_2$ and $O_2$ is (R = 8.0 J/K-mol)

Prashant Kotian · Accepted Answer

Correct answer: A. density d = pm_avg/rt → slope d/p = m_avg / rt = 1.2 × 10^-5. m_avg = 1.2 × 10^-5 × 8.0 × 300 = 0.0288 kg/mol = 28.8 g/mol. let mole fraction of n2 be x. m_avg = 28x + 32(1 - x) = 32 - 4x = 28.8 → 4x = 3.2 → x = 0.80. mole ratio n2 : o2 = 80 : 20, which is also the volume ratio.

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