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Thermodynamics

# Consider the reaction $N_2 + 3H_2 \rightarrow 2NH_3$ 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 expressions is true?

$\begin {array} {1 1} (A)\;\Delta H > \Delta U & \quad (B)\;\Delta H < \Delta U \\ (C)\;\Delta H = \Delta U & \quad (D)\;\Delta = 0 \end {array}$

$\Delta H = \Delta U = \Delta n_gRT$
$\Delta n_g$ = mole of (gaseous products – gaseous reactants) = -ve
Thus, $\Delta H < \Delta U$
Ans : (B)