Question 19N.3.SL.TZ0.b(ii)
| Date | November 2019 | Marks available | [Maximum mark: 2] | Reference code | 19N.3.SL.TZ0.b(ii) |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | b(ii) | Adapted from | N/A |
An ideal gas consisting of 0.300 mol undergoes a process ABCD. AB is an adiabatic expansion from the initial volume VA to the volume 1.5 VA. BC is an isothermal compression. The pressures at C and D are the same as at A.
The following data are available.
Pressure at A = 250 kPa
Volume at C = 3.50 × 10–3 m3
Volume at D = 2.00 × 10–3 m3
The gas at C is further compressed to D at a constant pressure. During this compression the temperature decreases by 150 K.
For the compression CD,
explain why the entropy of the gas decreases.
[2]
ALTERNATIVE 1
«from b(i)» is negative ✔
AND is negative ✔
ALTERNATIVE 2
T and/or V decreases ✔
less disorder/more order «so S decreases» ✔
ALTERNATIVE 3
T decreases ✔
✔
NOTE: Answer given, look for a valid reason that S decreases.
