Use Coupon: CART20 and get 20% off on all online Study Material

Total Price: Rs.

There are no items in this cart.
Continue Shopping
Rakshit Ramesh Grade: 11

Please help me solve this problem:

a vessel of volume 100ml contains 10 % oxygen and 90% of an unknown gas.

The gases diffuse in 86 sec through a small hole of the vessel. If pure oxygen under the same conditions diffuses in 75 sec,. find the molecular weight of the gas .

Thank you,

7 years ago

Answers : (1)

AJIT AskiitiansExpert-IITD
68 Points

Dear Rakshit ,

Graham's law of diffusiuon says -- the rate of diffusion of a gas is inversely proportional to the square root of it’s density or molecular weights. If r1 and r2 are the rates of diffusion of two gases, whose densities under the given conditions are d1 and d2 respectively, then we have


where M2and M1 are the molecular weights of the gases.

NOW , here molecular weight of oxygen  =  32

Let the molecular weight of gas be M , average molecular weight of gas mixture  =  (10*32 + 90 *M) /100 = 3.2 + .9 * M

Applying above law ,

          roxygen / rmixture  =   (Mmixture /Moxygen)1/2

         86/75 =( 3.2+ .9 *M / 32)1/2

solving we get = 43.19 gm




Please feel free to post as many doubts on our discussion forum as you can. We are all IITians and here to help you in your IIT JEE preparation.

Now you can win exciting gifts by answering the questions on Discussion Forum. So help discuss any query on askiitians forum and become an Elite Expert League askiitian.


7 years ago
Think You Can Provide A Better Answer ?
Answer & Earn Cool Goodies
  • Complete JEE Main/Advanced Course and Test Series
  • OFFERED PRICE: Rs. 15,900
  • View Details

Ask Experts

Have any Question? Ask Experts

Post Question

Answer ‘n’ Earn
Attractive Gift
To Win!!! Click Here for details