Applying the right formula to problem solving. It is often necessary to select the appropriate formula to solve a given problem. We have covered the formulae listed on the right. It is a matter of selecting the right formula given the information in the problem. Below are four examples with detailed solutions. Attempt all four then click on the solutions to see if you were correct. On an unknown planet a pure sample of hydrogen gas is placed in 450 litre balloon at a pressure of 80 kPa at a temperature of 23oC and allowed to ascend skywards. At an altitude of 2,330m the volume of the balloon is recorded to be 350 litres and the pressure 30 kPa. What is the temperature at 2,330m? Solution The tyres of a fighter jet have a volume of 45 litres each. Each tyre is pumped up to a pressure of 410 kPa at 22oC with pure nitrogen. Upon landing the tyres heat up to 117oC . The tyre manufacturer recommends that the tyres not be inflated beyond 600 kPa as a blow-out is likely to occur. Assuming the volume of the tyres remains constant is the pilot in danger of having a blow out? Solution What mass of nitrogen is placed in each tyre? Atomic mass N =14. Solution A 7.5 litre sample of oxygen gas at 284oC was heated, At what temperature would the volume be 10.0 litres assuming that the pressure remains constant? Solution A gas sample is stored in a cylinder at 284oC. If the pressure exerted on the gas is doubled and the gas is then heated to 354oC by what factor does the volume of the gas change? Clues