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 : option (B) 2, 1

explanation : general formula of alkane is $C_xH_{(2x+2)}$ and general formula of alkene is $C_yH_{2y}$.

case 1 : molar ratio of alkane and alkene is 2 : 1 and molecular weight of mixture is 20.

so, 2/3($C_xH_{(2x+2)}$) + 1/3($C_yH_{2y}$) = 20

or, 2 × (12x + 2x + 2) + (12y + 2y) = 60

or, 28x + 14y + 4 = 60

or, 2x + y = 4......(1)

case 2 : molar ratio = 1 : 2 and molecular weight = 24

so, 1/3(12x + 2x + 2) + 2/3(12y + 2y) = 24

or, 14x + 2 + 28y = 72

or, 14x + 28y = 70

or, x + 2y = 5 .....(2)

from equations (1) and (2),

x = 1 and y = 2

so, option (B) is correct choice.

Answer 2

Answer:

2 78

Explanation:

upper one answer is wrong he has use wrong method mine method is right but handwritting are little bit bad so I'm sorry for that but answer is correct