Question

Consider the reaction : $N_2+3H_2\to 2N{H}_3$ carried out at constant temperature and pressure. If $△H$ and $△U$ are the enthalpy and internal energy changes for the reaction, which of the following expressions is true?

• A. ∆H > =∆U
• B. ∆H < ∆U
• C. ∆H = ∆U
• D. ∆H = 0

Answer 1

The correct option is B

∆H < ∆U

$△H=△U+△nRTfor{N}_2+3H_2\to 2N{H}_3$

$△n_g=2-4=-2$

$\therefore △H=△U-2RTor△U=△H+2RT$

$\therefore △U>△H$

(or)

$△H<△U$