Question

Two identical flask X and Y contain 64g of methane and 100g of an unknown gas A2 respectively at 2atm and 300 K. What is the vapour density of the gas A2??? Pls reply fast......

Answer 1

As given flask are identical therefore the number of moles would be equal in both flasks.

From ideal gas equation PV=nRT

Let volume of both gases = V liter

Given that,

P= 2 atm , T= 300 K

$n= \frac{mass}{molar mass}$

for metane gas number of moles $n= \frac{64}{16} = 4$

let molar mass of unknown gas is M then,

number of moles for unknown gas $n = \frac{100}{M}$

On substituting all these values in ideal gas equation

We get,

$2*1= (4+\frac{100}{M})*0.0821*300$

$(4+\frac{100}{M}) = \frac{2}{24.63} =  0.081$

$\frac{100}{M} = 0.081-4 = -3.92$

Ignoring -ve sign

$M = \frac{100}{3.92} = 25.51$

As we know that vapor density = $\frac{Molar mass}{2}$

Therefore,

$V.D = \frac{25.51}{2} = 12.76$