Question

Temperature in a larger room should be measured by means of a gaseous thermometer. A glass tube with the internal volume of 80 cm³ was for this purpose filled with nitrogen at a temperature of 20°C and a press ure of 101.325 kPa. The tube was then slowly and steadily moved throughout the room. Due to the thermal expansion the gas at the higher temperature escapes from the tube and is captured above the liquid whose vapour pressure is negligible. The total volume of the gas escaped from the tube was 35 cm³ at a temperature of 20°C and a pressure of 101.32 5 kPa. Problems: 

1. How many moles of nitrogen were used to fill the glass tube? 

2. How many moles of nitrogen escaped from the tube at the higher temperature? 

3. Calculate the average temperature in the room under investigation if the thermal expansion of the glass tube is assumed to be negligible. 

4. Does anything change if instead of pure nitrogen, a mixture containing 50 volume % of nitrogen and 50 volume % of hydrogen is used? 

Answer 1

1. Filling of the tube: 

2. Escaped from the tube: 

Remained in the tube: 

n₃(N₂) = n₁ – n₂ = 1.87 × 10^-3 mol 

3. Temperature at which the amount of substance of nitrogen (n₃) takes a volume of V₁ (the mean temperature in the room under investigation): 

 

4. No change can occur in comparison with the preceding experiment.