Question

4. A and B are two identical vessels. A contains
15 g ethane at 1 atm and 298 K. The vessel B
contains 75 g of a gas X, at same tamperature and
pressure. The vapour density of X, is -
(1) 75
(2) 150
(3) 37.5
(4) 45​

Answer 1

Answer:

Option =(A) 75

Explanation:

As we learnt in  

Avogadro’s Law -

Volume - mole relationship

- wherein

\frac{V_{1}}{n_{1}}= \frac{V_{2}}{n_{2}}

 

\frac{15}{30}= \frac{75}{M_{B}}

M_{B}= 150                

\left (V.D. \right )_{B}= \frac{150}{2}= 75

Option 1)

75

Correct

Option 2)

150

Incorrect

Option 3)

37.5

Incorrect

Option 4)

45

Incorrect

Answer 2

Answer:

(1) 75

Explanation :

Pv = net here p, v, t are constant therefore n is constant now the ratio of given mass and molecular mass also will be constant

therefore

15/30 = 75 / molecular mass of gas which gives the unknown molecular mass as 150 .

now we know vapour density is

molecular mass / 2

therefore 150/ 2 = 75

Therefore answer is 75 .