| Date | May 2012 | Marks available | 2 | Reference code | 12M.2.HL.TZ1.10 |
| Level | Higher level | Paper | Paper 2 | Time zone | Time zone 1 |
| Command term | Calculate, Determine, Explain, and State | Question number | 10 | Adapted from | N/A |
Question
Part 2 Thermodynamics
A fixed mass of an ideal gas undergoes the three thermodynamic processes, AB, BC and CA, represented in the P–V graph below.
State which of the processes is isothermal, isochoric (isovolumetric) or isobaric.
Process AB:
Process BC:
Process CA:
The temperature of the gas at A is 300K. Calculate the temperature of the gas at B.
The increase in internal energy of the gas during process AB is 4100J. Determine the heat transferred to the gas from the surroundings during the process AB.
The gas is compressed at constant temperature. Explain what changes, if any, occur to the entropy of
(i) the gas.
(ii) the surroundings.
(iii) the universe.
Markscheme
process AB: isobaric;
process BC: isochoric / isovolumetric;
process CA: isothermal;
use of \(\frac{{{V_2}}}{{{V_1}}} = \frac{{{T_2}}}{{{T_1}}}\);
to give 750 K;
W=(PΔV=9×105×[5-2]×10-3=)2700;
Q=ΔU+W=4100+2700=6800J;
(i) same number of molecules occupy smaller volume, so disorder and hence entropy decrease;
(ii) heat flows from gas to surroundings, so temperature of surroundings increases, so entropy increases;
(iii) from second law, entropy of universe increases during any process;
Award [0] for simple statement of entropy increases/decreases.
