JEE Main On 8 April 2017 Question 27
Question: For a reaction, $ A(g)\to A(\ell );\Delta H=-3RT. $ The correct statement for the reaction is: [JEE Online 08-04-2017]
Options:
A) $ \Delta H=\Delta U=0 $
B) $ |\Delta H|<|\Delta U| $
C) $ |\Delta H|>|\Delta U| $
D) $ \Delta H=\Delta U\ne 0 $
Show Answer
Answer:
Correct Answer: C
Solution:
$\Delta n_g=0-1=-1$ Now as we know that,
$ \Delta H=\Delta U+\Delta n_gRT$
$ \Delta U=\Delta H-\Delta n_gRT$
$\Delta U=-3RT-(-1)RT=-2RT$
$|\Delta H|=|-3RT|=3RT$
$|\Delta U|=|-2RT|=2RT$
Hence $|\Delta H| \gt |\Delta U|$
