Question

Define
1) entropy
2) enthalpy and write the sign of $\Delta H$ and $\Delta S$ for the reaction:
$2Cl\left(g\right)\to C{l}_2\left(g\right)$

Answer 1

Solution:-

Entropy $\to$ It is a thermodynamic function that describes the randomness and disorder of molecules based on the number of different arrangements available to them in a given system or reaction.

Enthalpy $\to$ The change in enthalpy under such conditions is the heat absorbed or released by the system through a chemical reaction or by external heat transfer.

For the reaction-

$2{Cl}_{\left(g\right)}⟶{{Cl}_2}_{\left(g\right)}$

The given reaction represents the formation of chlorine molecule from chlorine atoms.

Here, the bond formation is taking place. Therefore, energy is being released. Thus, $\Delta H$ is negative.

Also, two moles of atoms have more randomness than one mole of a molecule. Since spontaneity is decreased, $\Delta S$ is negative for the given reaction.