Question

A flask contains 12 g of a gas of relative molecular mass 120 at a pressure of 100 atm was evacuated by means of a pump until the pressure was 0.01 atm, Which of the following is the best estimate of the number of molecules left in the flask (N₀ = 6 x 10²³ mol^-1) .

(A) 6 x 10¹⁹ 

(B) 6 x 10¹⁸ 

(C) 6 x 10¹⁷ 

(D) 6 x 10¹³

Answer 1

Correct option (B) 6 x 10¹⁸ 

Explanation : 

[Volume of the flask and temperature remain constant]

Number of molecules left in the flask = n₂ x N₀ = 6 x 10¹⁸