When 2 g of gas A is introduced into an evacuated flask kept of 25° C, the pressure was found to be 1 atmosphere. If 3 g of another gas B is then added to the same flask, the pressure becomes 1.5 atm. Assuming ideal behavior, the ratio of molecular weights (M A: M B ) is

Question

When 2 g of gas A is introduced into an evacuated flask kept of 25° C, the pressure was found to be 1 atmosphere. If 3 g of another gas B is then added to the same flask, the pressure becomes 1.5 atm. Assuming ideal behavior, the ratio of molecular weights (M A: M B ) is (A) 1: 3 (B) 3: 1 (C) 2: 3 (D) 3: 2

Tardigrade Admin · Accepted Answer

Moles propto Pressure i. (2/M w A ) propto 1 atm Pressure of B=1.5-1=0.5 atm ii. (3/M w B ) propto 0.5 atm (3/M w B ) × (M w A /2)=(0.5/1) (M w A /M w B )=0.5 × (2/3)=(1/3) ∴ M w A: M w B =1: 3

$1 : 3$

$3 : 1$

$2 : 3$

$3 : 2$

Q. When 2g of gas A is introduced into an evacuated flask kept of 25∘C, the pressure was found to be 1 atmosphere. If 3g of another gas B is then added to the same flask, the pressure becomes 1.5atm. Assuming ideal behavior, the ratio of molecular weights (MA​:MB​) is

1:3

3:1

2:3

3:2

Moles ∝ Pressure i. MwA​2​∝1atm Pressure of B=1.5−1=0.5atm ii. MwB​3​∝0.5atm MwB​3​×2MwA​​=10.5​ MwB​MwA​​=0.5×32​=31​ ∴MwA​:MwB​=1:3

$1 : 3$

$3 : 1$

$2 : 3$

$3 : 2$