Question

At 300 K, a sample of 3.0 g of gas A occupies the same volume as 0.2 g of hydrogen at 200 K at the same pressure. The molar mass of gas A is _____ g mol^–1. (nearest integer)
Assume that the behaviour of gases as ideal.
(Given: The molar mass of hydrogen (H₂) gas is 2.0 g mol^–1).

Answer 1

Correct Answer: 45

\(V_1\), Volume of \(0.2\ g\) \(H_2\) at \(200\ K\)
\(=\frac { 0.2 \times R \times 200}{2 \times P}\)
\(V_2\), Volume of \(3.0\ g\) of gas A at \(300\ K\)
\(= \frac {0.3 \times R \times 300}{M \times P}\)
Given that, \(V_1 = V_2\) 
\(⇒ \frac {0.2 \times R \times 200 }{ 2 \times P} = \frac {0.3 \times R \times 300}{M \times P}\)
\(M = 45\) g mol^-1

So, the answer is \(45\).