Q 1 :

Ice at –5°C is heated to become vapor with temperature of 110°C at atmosphere pressure. The entropy change associated with this process can be obtained from    [2025]

• ${\int }_{268K}^{273K}{C}_{p,m} dT+\frac{\Delta H_{m,\text{fusion}}}{T_f}+\frac{\Delta H_{m,\text{vaporisation}}}{T_b}+{\int }_{273K}^{373K}{C}_{p,m} dT+{\int }_{373K}^{383K}{C}_{p,m} dT$

   

• ${\int }_{268K}^{383K}{C}_p dT+\frac{\Delta H_{\text{melting}}}{273}+\frac{\Delta H_{\text{boiling}}}{373}$

   

• ${\int }_{268K}^{273K}\frac{C_{p,m}}{T} dT+\frac{\Delta H_{m,\text{fusion}}}{T_f}+\frac{\Delta H_{m,\text{vaporisation}}}{T_b}+{\int }_{273K}^{373K}\frac{C_{p,m}dT}{T} +{\int }_{373K}^{383K}\frac{C_{p,m}dT}{T}$

   

• ${\int }_{268K}^{383K}{C}_p dT+\frac{q_{\text{rev}}}{T}$

   

Q 2 :

One mole of an ideal gas at 350 K is in a 2.0 L vessel of thermally conducting walls, which are in contact with the surroundings. It undergoes isothermal reversible expansion from 2.0 L to 3.0 L against a constant pressure of 4 atm. The change in entropy of the surroundings $\left(\mathrm{\Delta S}\right)$ is ______ ${\mathrm{JK}}^{-1}$ (Nearest integer) Given: R = 8.314 J ${\mathrm{K}}^{-1}$ ${\mathrm{mol}}^{-1}$      [2023]

Q 3 :

30.4 kJ of heat is required to melt one mole of sodium chloride and the entropy change at the melting point is 28.4 J ${\mathrm{K}}^{-1}$ ${\mathrm{mol}}^{-1}$ at 1 atm. The melting point of sodium chloride is ________ K. (Nearest integer)            [2023]

Q 4 :

Which of the following reaction(s) has a positive entropy change?

I)  ${\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)\to \mathrm{AgCl}\left(\mathrm{s}\right)$

II)  ${\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{s}\right)\to {\mathrm{NH}}_3\left(\mathrm{g}\right)+\mathrm{HCl}\left(\mathrm{g}\right)$

III)  $2{\mathrm{NH}}_3\left(\mathrm{g}\right)\to {\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)$

• I and II 

   

• III only

   

• II & III 

   

• II only

   

Q 5 :

Consider the expansion of one mole of an ideal gas from an initial state to a final state, with $\mathrm{\Delta S}$ representing the entropy change in the process. The correct statement is:

• If the process is carried out reversibly, the value of $\mathrm{\Delta S}$ will be higher in comparison to its irreversible counterpart.

   

• If the process is adiabatic, the value of $\mathrm{\Delta S}$ is always zero, irrespective of whether the process is carried out reversibly or irreversibly.

   

• If the process is isothermal, there will not be any heat exchange with the surrounding since the temperatures of the system and the surrounding are equal.

   

• If the process is isothermal and the final volume is double of the initial volume, the value of $\mathrm{\Delta S}$ will be independent of the temperature.