Two containers A and B are joined by a tube of negligible volume, as illustrated in Fig. 2.1.

Question 1

(a) State what is meant by a mole. [2]

(b) Two containers A and B are joined by a tube of negligible volume, as illustrated in

Fig. 2.1.

Fig. 2.1

The containers are filled with an ideal gas at a pressure of 2.3 × 10⁵ Pa.

The gas in container A has volume 3.1 × 10³ cm³ and is at a temperature of 17 °C.

The gas in container B has volume 4.6 × 10³ cm³ and is at a temperature of 30 °C.

Calculate the total amount of gas, in mol, in the containers. [4]

Reference: Past Exam Paper – June 2011 Paper 42 & 43 Q2

Solution:

(a) A mole is an amount of a substance containing the same number of particles (atoms / molecules) as in 0.012kg of carbon-12.

(b)

pV = nRT

(n = pV / RT)

{total amount of gas, in mol, n = n_A + n_B}

 

Total amount = (2.3×10⁵ × 3.1×10^-3) / (8.31×290) + (2.3×10⁵ × 4.6×10^-3) / (8.31×303)

Total amount = 0.296 + 0.420 = 0.716 mol