Question

0.5 dm3 flask contains gas A (density=3 g dm-3)
and another flask of 1 dm3 contains gas B
(density = 1.5g dm-3) at same temperature. If mo-
lar mass of A is one half of molar mass of B, then
ratio of pressures exerted by the gases A and B is
(1) 2:1
(2) 1:1
13 4:1
(4) 3:1
2​

Answer 1

Dear Student,

◆ Answer - (3)

Pa : Pb = 4 : 1

● Explanation -

No of moles of gas A is -

na = Wa / Ma

na = Va × da / Ma

na = 0.5 × 3 / Ma

na = 3/2Ma

No of moles of gas B is -

nb = Wb / Mb

nb = Vb × db / 2Ma

nb = 1 × 1.5 / 2Ma

nb = 3/4Ma

Applying gas laws,

PaVa/na = PbVb/nb

Pa × 0.5 / (3/2Ma) = Pb × 1 / (3/4Ma)

Pa × Ma/3 = Pb × 4Ma/3

Pa/Pb = 4

Therefore, ratio of pressures is Pa:Pb = 4:1.

Thanks dear...

Answer 2

Answer:

4:1

Explanation:

number of moles of gas A

na=wa/ma

na=va*da/ma

na=0.5*3/ma

na=1.5/ma

na=3/2ma

number of moles of gas B

mb=wb/mb

nb=vb*db/2mb

nb=3/4mb

PaVa/na=PbVb/nb

pa0.5/3/2ma = pb1.5/3/4

pa:pb=4:1