Question

Two grams of gas A are introduced in a evacuated flask at 25°C. The pressure of the gas is 1 atm. Now 3g of another gas B is introduced in the same flask, the total pressure becomes 1.5 atm. Calculate

(a) the ratio of molecular mass M_A and M_B

(b) volume of the vessel, if A is O₂. 

Answer 1

For gas A : Its mass = 2g;

P_A =  1atm , T = 298 K 

 For gas B : Its mass = 3g,

P_B = 0.5 atm. T = 298 K

According to Dalton’s law of partial pressure

P = P_A + P_B

1.5 = 1 + P_B 

p_B = 0.5 atm

Now,  PV = wRT/m

For gas A :   p_A = 1atm, m =  M_A , w = 2g