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For the reaction, $2Cl(g)\rightarrow Cl_2(g)$, the correct option is:
A
$\Delta_rH>0$ and $\Delta_rS<0$
B
$\Delta_rH0$
C
$\Delta_rH<0$ and $\Delta_rS<0$
D
$\Delta_rH>0$ and $\Delta_rS>0$
Detailed Solution
$Cl_2(g) \rightarrow 2Cl(g)$ is endothermic (energy is needed to break the bond), so the reverse reaction $2Cl(g) \rightarrow Cl_2(g)$ is exothermic: $\Delta_rH < 0$.
Two gaseous atoms combine to form one gaseous molecule, so randomness decreases: $\Delta_rS < 0$.