Let the first vapour density be D And the other vapour density be d. Then, D/d = 9/8 --------- (1) we know that vapour density = molecular mass/2 So, Let first molecular mass be M and other moleculr mass be m Then, M/m = 9/8
Therefore, rms I / rms II = [(3RTm)^1/2] / [(3RTM)^1/2] = [(m/M)^1/2] = [(8/9)^1/2] = 2*2^1/2 : 3 This is the required answer.
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