When 1 g of an ideal gas A is introduced into an evacuated vessel at 400 K, the pressure was found to be 1 atm. Three grams of another ideal gas B is then added to A and the pressure is now found to b

Question

When 1 g of an ideal gas A is introduced into an evacuated vessel at 400 K, the pressure was found to be 1 atm. Three grams of another ideal gas B is then added to A and the pressure is now found to be 4/3 atm. What is the ratio between the average speeds of A and B at the same temperature?

TestHub · Accepted Answer

B contributes p B = 4/3 - 1 = 1/3 atm. At fixed V, T: n A : n B = 1 : 1/3 = 3:1. With n A = 1/M A , n B = 3/M B : (1/M A )/(3/M B ) = 3 ⇒ M B = 9M A . Average speed ratio u av,A : u av,B = √(M B /M A ) = 3:1. Confirms Ans (a) 3:1.

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