Question

For which of the following reaction $\Delta H\ne \Delta U$:

• A. $H_2\left(g\right)+C{l}_2\left(g\right)\to 2HCI\left(g\right)$
• B. $N_2\left(g\right)+3H_2\left(g\right)\to 2N{H}_3\left(g\right)$
• C. $N{H}_{4}HS\left(s\right)\to N{H}_3\left(g\right)-H_{2}S\left(g\right)$
• D. $CaC{O}_3\left(s\right)\to CaO\left(s\right)+C{O}_2\left(g\right)$

Answer 1

The correct option is A $H_2\left(g\right)+C{l}_2\left(g\right)\to 2HCI\left(g\right)$

$△H=△U$ if $△n=0$

$△H\ne △U$ if $△n\ne 0$

(a) $△n=2-2=0$

(b) $△n=2-4=-2$

(c) $△n=2-0=2$

(d) $△n=1-0=1$