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 $



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