ExamGOAL
Books
51
Subjective

Match the following.

List I List II
A. Adiabatic process 1. Heat
B. Isolated system 2. At constant volume
C. Isothermal change 3. First law of thermodynamics
D. Path function 4. No exchange of energy and matter
E. State function 5. No transfer of heat
F. $$\Delta U=q$$ 6. Constant temperature
G. Law of conservation of energy 7. Internal energy
H. Reversible process 8. $$p_{ext=0}$$
I. Free expansion 9. At constant pressure
J. $$\Delta H=q$$ 10. Infinitely slow process which proceeds through a series of equilibrium states.
K. Intensive property 11. Entropy
L. Extensive property 12. Pressure
13. Specific heat

Explanation

$$\begin{aligned} &\begin{aligned} & \text { I. } \rightarrow(8) \quad \text { J. } \rightarrow(9) \quad \text { K. } \rightarrow(1,12,13) \quad \text { L. } \rightarrow(7,11) \end{aligned}\\ &\text { I. } \rightarrow(8) \quad \text { J. } \rightarrow(9) \quad \text { K. } \rightarrow(1,12,13) \quad \text { L. } \rightarrow(7,11) \end{aligned}$$

Correct matching can be done as

A. Adiabatic process No transfer of heat
B. Isolated system No exchange of energy and matter
C. Isothermal change Constant temperature
D. Path function Heat
E. State function Internal energy
Entropy
Pressure
F. $$\Delta U=q$$ At constant volume
G. Law of conservation of energy First law of thermodynamics
H. Reversible process Infinitely slow process which proceeds through a series of equilibrium states
I. Free expansion $$p_{ext}=0$$
J. $$\Delta H=q$$ At constant pressure
K. Intensive property Heat
Pressure
Specific heat
L. Extensive property Internal energy
Entropy

52
Subjective

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

Explanation

$$\mathrm{A.\to(2)\quad B.\to(3)\quad C.\to(1)}$$

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, $\Delta S=0$

53
Subjective

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

Explanation

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.

54
Subjective

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. $$\frac{\Delta H_{vap}}{T_b}$$

Explanation

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.

55
MCQ (Single Correct Answer)

Assertion (A) Combustion of all organic compounds is an exothermic reaction.

Reason (R) The enthalpies of all elements in their standard state are zero.

A
Both $A$ and $R$ are true and $R$ is the correct explanation of $A$
B
Both $A$ and $R$ are true but $R$ is not the correct explanation of $A$
C
$A$ is true but $R$ is false
D
$A$ is false but $R$ is true