Question

For a reaction, A(g) --> A(l); ΔH=−3RT. The correct statement for the reaction is:
(1) ΔH = ΔU not= O
(2) ΔH = ΔU = O
(3) |H| < |ΔU|
(4) |ΔH| > |ΔU|

Answer 1

Answer: (4) |ΔH| > |ΔU|

Explanation: Enthalpy(H) and internal energy(U) are related as:

$\Delta H=\Delta U+(\Delta n_g){RT}$

$(\Delta n_g)$= no of moles of gaseous products - number of moles of gaseous reactants

$A(g)\rightarrow A(l)$

$(\Delta n_g)$= 0 - 1 = -1

$-3RT=\Delta U+(-1){RT}$

$\Delta U= -3RT+RT=-2RT$

|ΔH| > |ΔU| as 3RT > 2RT

Answer 2

Answer : |H|>|U|

Hope it helps you