Solved: CHEMISTRY Question for NEET

NEET CHEMISTRYEasy

For the reaction, $2\text{Cl(g)} \rightarrow \text{Cl}_2\text{(g)}$ , the correct option is:

$\Delta_r H > 0$ and $\Delta_r S > 0$

$\Delta_r H > 0$ and $\Delta_r S < 0$

$\Delta_r H < 0$ and $\Delta_r S < 0$

$\Delta_r H < 0$ and $\Delta_r S > 0$

Let us analyze the given reaction: $2\text{Cl(g)} \rightarrow \text{Cl}_2\text{(g)}$

Enthalpy change ( $\Delta_r H$ ): The reaction involves the formation of a $\text{Cl-Cl}$ bond from two isolated gaseous chlorine atoms. Bond formation is an exothermic process because energy is released when a stable bond is formed. Therefore, the enthalpy change is negative ( $\Delta_r H < 0$ ).
Entropy change ( $\Delta_r S$ ): In this reaction, two moles of gaseous atoms combine to form one mole of a gaseous molecule. Since the number of gaseous particles decreases ( $\Delta n_g = 1 - 2 = -1$ ), the randomness or disorder of the system decreases. Therefore, the entropy change is also negative ( $\Delta_r S < 0$ ).

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