Calculate the temperature of the gas in state B.

(i) Calculate the work done by the gas in expanding from state A to state B.

(ii) Determine the amount of thermal energy transferred during the expansion from state A to state B.

The gas is isothermally compressed from state B back to state A.

(i) Using the P–V diagram axes opposite, draw the variation of pressure with volume for this isothermal compression.

(ii) State and explain whether the magnitude of the thermal energy transferred in this case would be less than, equal to or greater than the thermal energy transferred in (b)(ii).

realization that since pV = constant, the temperature must be the same i.e. 400 K / full calculation using gas law to get 400 K;

(i) work done is area under curve;
and this is \(\left( {\frac{{4.0 + 8.0}}{2} \times 4 \times {{10}^2}} \right) = 2400{\rm{J}}\);
Award [2] for correct bald answer.

(ii) (Q=ΔU+W with) ΔU=0;
so Q=2400J;
Award [0] for correct answer with no or wrong argument.

(i) curve under given straight line starting at B and ending at A;

(ii) it would be less;
since the work done would be less / area under curve is less (and ΔU = 0 );