Match the following processes with entropy change
| Reaction | Entropy change | ||
|---|---|---|---|
| A. | A liquid vaporises | 1. | $$\Delta S=0$$ |
| B. | Reaction is non-spontaneous at all | 2. | $$\Delta S$$ = positive |
| C. | Reversible expansion of an ideal gas | 3. | $$\Delta S$$ = negative |
$$\mathrm{A.\to(2)\quad B.\to(3)\quad C.\to(1)}$$
A. When a liquid vaporises, i.e., liquid $\rightarrow$ vapour, entropy increase i.e., $\Delta S=$ positive
B. When $\Delta H=$ positive, i.e., energy factor opposes. The process is non-spontaneous at all temperatures if entropy factor also opposes the process, i.e., $\Delta S=$ negative
C. In the reversible expansion of an ideal gas, the system remains in equilibrium at every stage. Hence, $\Delta S=0$
Match the following parameters with description for spontaneity.
| $$\Delta$$ (Parameters) $$\Delta_r H^s \Delta_r S^s \Delta_r G^s$$ |
Description | ||
|---|---|---|---|
| A. | + $$-$$ + | 1. | Non-spontaneous at high temperature |
| B. | $$-$$ $$-$$ + at high T | 2. | Spontaneous at all temperatuers |
| C. | $$-$$ + $$-$$ | 3. | Non-spontaneous at all temperatures |
A. $\rightarrow$ (3)
B. $\rightarrow$ (1)
C. $\rightarrow$ (2)
A. When $\Delta_r G^{\mathrm{s}}$ is positive, reaction is non-spontaneous at all temperatures
B. When $\Delta_r G^{\mathrm{s}}$ is positive at high temperature means the reaction is non-spontaneous at high temperature.
C. When $\Delta_r H^{\mathbb{S}}=$ negative means it favours, $\Delta_r S^{\mathbb{s}}=$ positive means it also favours. $\Delta_r G^{\circ}=$ negative means reaction is spontaneous at all temperatures.
Match the following
| A. | Entropy of vaporisation | 1. | decreases |
|---|---|---|---|
| B. | K for spontaneous process | 2. | is always positive |
| C. | Crystalline solid state | 3. | lowest entropy |
| D. | $$\Delta U$$ in adiabatic expansion of ideal gas | 4. | $$\frac{\Delta H_{vap}}{T_b}$$ |
A. $\rightarrow(2,4)$
B. $\rightarrow$ (2)
C. $\rightarrow$ (3)
D. $\rightarrow$ (1)
A. Entropy of vaporisation is always positive. It is equal to $\Delta H_{\text {vap }} / T_b$
B. $\Delta_r G^{\circ}=-R T \ln K$
If $K$ is positive, $\Delta_r G^{\circ}=$ negative and reaction is spontaneous.
C. Crystalline solid state has lowest entropy.
D. During adiabatic expansion of an ideal gas, $q=0$. Hence, $\Delta U=q+W$ gives $\Delta U=W$, i.e., work done is at the cost of internal energy which decreases.
Assertion (A) Combustion of all organic compounds is an exothermic reaction.
Reason (R) The enthalpies of all elements in their standard state are zero.
Assertion (A) Spontaneous process is an irreversible process and may be reversed by some external agency.
Reason (R) Decrease in enthalpy is a contributory factor for spontaneity.