Q. The molecular weight of air will be (the components of air given as $N_{2} - 78\%,O_{2} - 21\%,Ar - 09\%\$and $CO_{2} - 0.1\%)$
A) 18.64
B) 24.968
C) 28.964
D) 29.864
Explanation
(c)
In air
Molecular weight of $N_{2} = \frac{28 \times 78}{100} = 21.84$
Molecular weight of $O_{2} = \frac{32 \times 21}{100} = 6.72$
Molecular weight of $Ar = \frac{18 \times 0.9}{100} = 0.162$
Molecular weight of ${CO}_{2} = \frac{44 \times 0.1}{100} = 0.044$
So, molecular weight of air = 21.84 + 6.72 + 0.162 +0 .044
= 28.766
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.