Question

In a gaseous mixture an alkane (CH2x+2) and an alkene (CH) are taken in 2:1 mole ratios, the average
molecular weight of mixture is observed to be 20. If the same alkane and alkene are taken in
1:2 mole ratios, the average molecular weight of mixture is observed to be 24. Then the value of x' and y
respectively are :
(A) 2.1
(B) 1,2
(C) 2,3
(D) 3,2​

Answer 1

Answer:

the correct option for that question is 2:1 that is option B

If the alkane, CxH2x+2 and alkene, CyH2y is in the ratio of 2:1, then

Mmix=2.(14x+2)+1.(14y)3=20

28x+14y=56 ...( 1 )

If the alkane, CxH2x+2 and alkene, CyH2y is in the ratio of 1:2, then

Mmix=1.(14x+2)+2.(14y)3=24

14x+28y=70 ...( 2 )

Solving equation (1) and (2), we get

x=1,y=2