Question

1 L of a gas at STP weight 1.964 g. What is vapour
density of the gas?
(1) 11
(2) 22
(3) 44
(4) 88
​

Answer 1

Answer:

(2) 22 is vapour density of the gas

Explanation:

22.4L of gas at STP contain 1 mole of the gas.

1L of gas at STP contain 1/22.4 moles of the gas.

no. of moles=given gram mass/gram molecular mass

1/22.4=1.964/gram molecular mass

gram molecular mass=1.964/(1/22.4)

gram molecular mass=1.964*22.4

therefore

gram molecular mass=43.9936g

vapour density=molecular mass/2

therefore

vapour density of the gas =molecular mass of the gas/2

=43.9936/2

=21.9968g

=22(approx.)