Question

The average molecular speed is greatest in which of the following gas samples ?

• A. 1.0 mol of O₂ at 560 K
• B. 0.50 mol of Ne at 500 K
• C. 0.20 mol of CO₂ at 440 K
• D. 2.0 mol of He at 140 K

Answer 1

Answer: (D)

2.0 mol of He at 140 K

Answer 2

Average molecular speed =$\sqrt{\frac{8RT}{\pi M}}$is dependent on T and M

Thus, greater the value of $\sqrt{\frac{T}{M}}$, greater the molecular speed.

Thus, Gas$\sqrt{\frac{T}{M}}$

O₂$\sqrt{\frac{560}{32}}$ 4.18

Ne$\sqrt{\frac{500}{20}}$ 5.0

O₂$\sqrt{\frac{440}{44}}$ 3.16

He$\sqrt{\frac{140}{4}}$ 5.91