Chemical Thermodynamics Question 342
Question: What is the value of change in internal energy at 1 atm in the process-
$ H_2O( 1,323K )\xrightarrow{{}}H_2O( g,423K ) $
Given: $ {C_{v,m}}(H_2O,I)=75.0J{{K}^{-1}}mo{{l}^{-1}} $ ; $ {C_{p.m}}(H_2O,g)=33.314J{{K}^{-1}}mo{{l}^{-1}} $
$ \Delta H_{vap},at,373,K=40.7,kJ\text{/}mol $
Options:
A) $ 42.91kJ/mol $
B) $ 43086kJ/mol $
C) $ 42.6kJ/mol $
D) $ 49.6kJ/mol $
Show Answer
Answer:
Correct Answer: C
Solution:
$ {C_{v,m}}(H_2O,g)=33.314-8.314 $
$ =25J/Kmol $
$ \Delta U_2=\Delta H_2-\Delta n_{g}RT=37.6 $
$ \Delta U_{total}=\Delta u_1+\Delta u_2+\Delta u_3 $
$ ={C_{v,m}}(l)\Delta T+\Delta V_{vap}+{C_{v,m}}(g)\Delta T $
$ =\frac{75\times 50}{1000}+37.6+\frac{25\times 50}{1000} $
$ =42.6kJ/mol $
