Question

Temp.& pressure same,rate of diffusion of H2 gas is 3√3 times that of CnH2n-2.Find n?​

Answer 1

Explanation:

Answer ⇒ n = 1.

It is given confusing in question about mol. formula. As what I thinks, It should be,

Explanation ⇒ By the Graham's Law of diffusion, the rate of diffusion of any gas is inversely proportional to the square root of Molar mass of that gas.

Let Molar mass of Hydrocarbon be M and that of Hydrogen be m.

Let rate of diffusion of Hydrocarbon be R and that of Hydrogen be r.

Then,   R/r = √(m/M)

It is given, rate of diffusion of Hydrogen = 3 × rate of diffusion of Hydrocarbon.

∴ r = 3R

Putting this in Graham's equation, we get,

R/3R = √(m/M)

∴ 1/9 = m/M

∴ M = 9m

∴ M = 9 × 2 [Molar mass of Hydrogen = m = 2 g/mole.]

∴ M = 18 g/mole.

Now, Molar mass of hydrocarbon = 12n + (2n + 2)1

= 12n + 2n + 2

= 14n + 2

∴ 14n + 2 = 18

∴ n = 16/14

∴ n = 8/7

∴ n ≈ 1

∴