Question

In a common classroom demonstration, a balloon is filled with air and submerged in liquid nitrogen. The balloon contracts as the gases within the balloon cool. Suppose the balloon initially contains 2.90 L of air at a temperature of 21.5 ∘C and a pressure of 0.996 atm .

Part A

Calculate the expected volume of the balloon upon cooling to -196 ∘C (the boiling point of liquid nitrogen). When the demonstration is carried out, the actual volume of the balloon decreases to 0.61 L.

Part B

Can you explain the difference between the observed volume of the balloon and calculated value?

Answer 1

Hi, since the final pressure is not given. it will affect our final values. If we had final pressure inside the balloon we would have used

since we do not have the both initial and final pressure values, we will have to use only

If you can provide me the final pressure, I would happily do the calculations for you.

Well the temperatures in Kelvin units are

and

and

This is a very simple condition, not accounting for the fact that oxygen has a boiling point of 90 K so oxygen will be in liquid form at the boiling point of nitrogen. This is why the observed volume is smaller than the calculated volume since oxygen has turned into liquid and only nitrogen is left in the balloon. Since there is 21 % oxygen in air so the air volume should be reduced by 21 % or we can say that the volume left is only 79 % of the expected value. This is .

Hope that helps. If you need more information, please do not hesitate to ask.