# Class 11 Chemistry States of Matter: NCERT Solutions for Question 18

This page focuses on the detailed States of Matter question answers for Class 11 Chemistry States of Matter, addressing the question: '2.9 g of a gas at 95 °C occupied the same volume as 0.184 g of dihydrogen at 17 °C, at the same pressure. What is the molar mass of the gas?'. The solution provides a thorough breakdown of the question, highlighting key concepts and approaches to arrive at the correct answer. This easy-to-understand explanation will help students develop better problem-solving skills, reinforcing their understanding of the chapter and aiding in exam preparation.
Question 18

## 2.9 g of a gas at 95 °C occupied the same volume as 0.184 g of dihydrogen at 17 °C, at the same pressure. What is the molar mass of the gas?

From the gas equation,

PV = (w/M) RT

Substituting the given data in the gas equation, we get

PV = (2.9 / M) x R x 368

&

PV = (0.184 / 2) x R x 290

From these two equation, we can write

(2.9 / M) x R x 368 = (0.184 / 2) x R x 290

By, striking throug R from both side, we get

(2.9 / M) x 368 = (0.184 / 2) x 290

Or

(2.9 / M)   =  (0.092 X 290) / 368

Or

M  = 2.9 x 368 / 0.092 x 290

= 40 g/mol

Hence, the molar mass of the gas is 40 g mol–1.