Chemical Thermodynamics Question 371
Question: The molar heat capacity $ ( C_{p} ) $ of $ CD_2O $ is 10 cals at 1000 K. The change in entropy associated with cooling of 32 g of $ CD_2O $ vapour from 1000 K to 100 K at constant pressure will be: (D = deuterium, atomic mass = 2 u)
Options:
A) $ 23.03calde{{g}^{-1}} $
B) $ -23.03calde{{g}^{-1}} $
C) $ 2.303calde{{g}^{-1}} $
D) $ -2.303calde{{g}^{-1}} $
Show Answer
Answer:
Correct Answer: B
Solution:
- Given, $ C_{P}=10 $ cals at 1000 K $ T_1=1000K.,T_2=100K $
$ m=32,g $
$ \Delta S=- $ at constant pressure $ \Delta S=C_{p} $ In $ \frac{T_2}{T_1} $
$ =2.303\times C_{p}log\frac{T_2}{T_1} $
$ =2.303\times 10log\frac{100}{1000} $
$ =-23.03calde{{g}^{-1}} $
