Thermodynamics's Question 53 | Chemistry XI - Part 1 | NCERT Exemplar Questions

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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.

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.

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.

Both $A$ and $R$ are true and $R$ is the correct explanation of $A$

Both $A$ and $R$ are true but $R$ is not the correct explanation of $A$

$A$ is true but $R$ is false

$A$ is false but $R$ is true

MCQ (Single Correct Answer)

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.

Both $A$ and $R$ are true and $R$ is the correct explanation of $A$

Both $A$ and $R$ are true but $R$ is not the correct explanation of $A$

$A$ is true but $R$ is false

$A$ is false but $R$ is true

MCQ (Single Correct Answer)

Assertion (A) A liquid crystallises into a solid and is accompanied by decrease in entropy. Reason (R) In crystals, molecules organise in an ordered manner.

Both $A$ and $R$ are true and $R$ is the correct explanation of $A$

Both $A$ and $R$ are true but $R$ is not the correct explanation of $A$

$A$ is true but $R$ is false

$A$ is false but $R$ is true

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