Which of the following molecules has the largest root mean square velocity at 25°C

Options

(a) NH₃
(b) SO₂
(c) H₂S
(d) CO₂

Correct Answer:

NH₃

Explanation:

Temperature= 25⁰C, R.M.S velocity (ν r.m.s) = √(3RT / M ) ∝ √(1/M) .
(where M is molecular weight). We also known that molecular weights of SO₂, CO₂, NH₃, H₂S are 64 , 44 , 17 , 34 respectively .Therefore NH₃ molecule has the largest root mean square velocity, because of the least molecular weight.