Chemical Thermodynamics Question 99

Question: Consider the reaction : $ N_2+3H_2\to 2NH_3 $ carried out at constant temperature and pressure. If $ \Delta H $ and $ \Delta U $ are the enthalpy and internal energy changes for the reaction, which of the following expression is true [AIEEE 2005]

Options:

A) $ \Delta H=0 $

B) $ \Delta H=\Delta U $

C) $ \Delta H<\Delta U $

D) $ \Delta H>\Delta U $

Show Answer

Answer:

Correct Answer: C

Solution:

At constant P or T $ \Delta H=\Delta U+\Delta nRT $

Þ $ \Delta n=n_{p}-n_{R}=2-4=-2 $

$ \therefore $ $ \Delta H<\Delta U $ .



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