QuestionGaseous state / molecular speed
Which one of the following gas samples will have the highest average molecular speed? (Atomic weight of O = 16, Ne = 20, C = 12 and He = 4)
- (a) 1.0 mole of O₂ at 560 K
- (b) 0.50 mole of Ne at 500 K
- (c) 0.20 mole of CO₂ at 440 K
- (d) 2.0 mole of He at 140 K
Answer: (d) 2.0 mole of He at 140 K
Mean speed ∝ √(T/M); amount of gas does not matter. O₂ √(560/32) = 4.18; Ne √(500/20) = 5.00; CO₂ √(440/44) = 3.16; He √(140/4) = 5.92 → highest → (d).