Date | November 2019 | Marks available | 3 | Reference code | 19N.3.SL.TZ0.6 |
Level | Standard level | Paper | Paper 3 | Time zone | 0 - no time zone |
Command term | Determine | Question number | 6 | Adapted from | N/A |
Question
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,
Show that the pressure at B is about 130 kPa.
Calculate the ratio VAVC.
determine the thermal energy removed from the system.
explain why the entropy of the gas decreases.
state and explain whether the second law of thermodynamics is violated.
Markscheme
PB=250×1031.553 «from PB(1.5 VA)53=250×103×VA53» ✔
= 127 kPa ✔
«127×103×1.5 VA=250×103 VC»
1.31 ✔
ALTERNATIVE 1
work done ∆ ✔
change in internal energy
OR
✔
thermal energy removed
OR
✔
ALTERNATIVE 2
✔
thermal energy removed ✔
✔
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.
not violated ✔
the entropy of the surroundings must have increased
OR
the overall entropy of the system and the surroundings is the same or increased ✔