Question

Given a sample of one mole of the indicated gas at the following conditions

Which of the following has the highest molecular speed?

• A. $He$ at ${100}^{\circ }C$ and 1 atm
• B. $He$ at ${25}^{\circ }C$ and 1 atm
• C. $Ar$ at ${25}^{\circ }C$ and 1 atm
• D. $Ar$ at ${25}^{\circ }C$ and 2 atm
• E. $Ar$ at $0^{\circ }C$ and 1 atm

Answer 1

The correct option is A $He$ at ${100}^{\circ }C$ and 1 atm

We know, $V\alpha \sqrt{\frac{T}{M}}$

i.e, more is the temperature and less is the molar mass higher is the molecular speed therefore $He$ at ${100}^{0}C$ (molar mass $=4$) has higher molecular speed.