Question

For a gas isotherm of d/p (y-axis) v/s pressure (P) (x-axis) passes through the points (4, 2.5) and (10, 5.5). The molar mass of gas is – (T = 300 K, density d in g/L and P in atm)

• A. 12.3 g/mol
• B. 24.6 g/mol
• C. 6.1 g/mol
• D. Cannot predict as gas may be real

Answer 1

Answer: (A)

12.3 g/mol

Answer 2

Let d/p = A (P) + B

solving, A = B = 0.5 ̃ $\left( \frac{d}{p} \right)_{P \rightarrow 0}$ = B = 0.5

As gas is real, M = $\left( \frac{d}{p} \right)_{P \rightarrow 0}$ RT

= 0.5 × 0.082 × 300

= 12.3 g/mol