Question

7 gm of a gas at 25 c occupies the same volume as of 0.184 gm of hydrogen at 17 c and at the same pressure.What is the molecular mass of th gas

Answer 1

HERE IS YOUR ANSWER

Given, moles = mass/mol.wt

Mass of gas = 3.7 g, mass of hydrogen = 0.184g

T1­ = 298K, T2 = 17oC = 273 + 17 = 290K

Moles of H2 = n1 = Mass/M. wt. = 0.184/2 = 0.092

Moles of gas = n2 = Mass/M. wt. = 3.7/M

For hydrogen P1V1 = n1RT1 …………..(i)

For gas P2V2 = n2RT2 …………….(ii)

(∵ Pressure and volume of gas |are same)

∴ From equation (i) and equation (ii)

P1V1/P1V1 = n1RT1/n2RT2 or 1 = 0.092 *298/n2 *290

or n2 = 0.092 *298/290 or 3.7/M = 0.092 *298/290

or 3.7/M = 0.0945

∴ M = 3.7/0.0945 = 39.15
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