Question

A neutral gas that is made of nitrogen and hydrogen only contains 7 g of nitrogen is in a mixture of with total mass 17 g, what is the mass fraction of the gas?

(a) 0.5

(b) 0.25

(c) 0.45

(d) 0.8

This question was addressed to me in examination.

The above asked question is from Mole Fraction and Mass(Weight) Fraction topic in division Moles, Density & Concentration of Basic Chemical Engineering

Answer 1

Correct answer is (a) 0.5

The best explanation: The neutral gas that is made of nitrogen and hydrogen is NH3, => moles of nitrogen = moles of NH3 = 7/14 = 0.5, => mass of hydrogen = 1.5*1 = 1.5 g => total mass of NH3 = 7 + 1.5 = 8.5 g, => mass fraction = 8.5/17 = 0.5.