Question 1

Paper 2Hard10 marks

A fixed amount of gas is measured in a cylinder with a movable piston. Figure 1 shows the measured pressure–volume states of the gas at two temperatures. The temperatures are in kelvin. XX is a further state of the same gas, at an unrecorded temperature. No curves have been fitted to the measurements.

00.511.522.533.5020406080100120140160180200V / LP / kPa● 300 K■ 450 K◆ X◆
(a)

Describe the pressure–volume relationship indicated by the 300 K300\ \mathrm{K} measurements.

[1]
(b)

For the measurements at V=2.00 LV=2.00\ \mathrm{L} calculate PV/TPV/T at each temperature. Give an appropriate unit.

[2]
(c)

A fixed amount of gas changes from state 1 (P1,V1,T1)(P_1,V_1,T_1) to state 2 (P2,V2,T2)(P_2,V_2,T_2) Using the empirical pressure–temperature law at constant volume and Boyle’s law at constant temperature, derive a relation between these two states. Temperatures are in kelvin.

[2]
(d)

A controller is expected to switch when the gas reaches 750 K750\ \mathrm{K} Use state XX and both calibration results from part (b) to estimate the temperature at XX and decide whether the controller’s reported temperature is consistent with the measurements. Show your working.

[5]

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