Thermodynamics · Chemistry · COMEDK

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MCQ (Single Correct Answer)

1
Two moles of an ideal gas at 1 bar pressure and 298 K is expanded into vacuum to double the volume. The work done is :
COMEDK 2025 Evening Shift
2
In the decomposition of limestone to lime, the values of $\Delta H^o$ and $\Delta S^o$ are $+179.1 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and $160.2 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$. Calculate the temperature above which conversion of limestone to lime will be spontaneous, if values of $\Delta H^o$ and $\Delta S^o$ remain unchanged with temperature. [Assuming pressure 1 bar ]
COMEDK 2025 Evening Shift
3
The enthalpies of combustion of $\mathrm{H}_2, \mathrm{C}$ (graphite) and $\mathrm{C}_2 \mathrm{H}_6(\mathrm{~g})$ are $-286.0,-394.0$ and $-1560.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$ at $25^{\circ} \mathrm{C}$ and 1 atm pressure. The enthalpy of formation of ethane is :
COMEDK 2025 Evening Shift
4
The Enthalpy of combustion of 1.0 mole of a reactive metal X at $27^{\circ} \mathrm{C}$ and 1.0 bar pressure to form a solid oxide ( XO ) is $-601.83 \mathrm{~kJ} / \mathrm{mol}$. The Internal energy change for this reaction is ___________ kJ. $$\left(\mathrm{R}=8.314 \mathrm{j} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right)$$
COMEDK 2025 Afternoon Shift
5
For a hypothetical chemical reaction $\mathrm{A}_2+3 \mathrm{~B}_2+$ Heat $\cdots\rightarrow 2 \mathrm{AB}_3$, which one of the following combinations of state variables would support the spontaneity of the reaction at a particular temperature?
COMEDK 2025 Afternoon Shift
6
For the reaction $\mathrm{A}_2+\mathrm{B}_2 \cdots \cdots>2 \mathrm{AB}, \Delta \mathrm{H}_{\mathrm{f}}=-400 \mathrm{~kJ} / \mathrm{mol}$. The bond dissociation enthalpies of $\mathrm{A}_2$, $\mathrm{B}_2$ and AB are in the ratio $1: 0.75: 1$. What is the bond dissociation enthalpy of $\mathrm{B}_2$ in $\mathrm{kJ} / \mathrm{mol}$ ?
COMEDK 2025 Afternoon Shift
7
0.4 g of Propane burns completely at 300 K in a bomb calorimeter. The temperature of the calorimeter and surrounding water rises by $0.4^0 \mathrm{C}$. If the heat capacity of the calorimeter and contents is $24 \mathrm{~kJ} \mathrm{~K}^{-1}$ what is the Enthalpy for the reaction? (Assume that propane gas shows ideal behaviour).
COMEDK 2025 Morning Shift
8
For a reaction $\mathrm{X}_2(\mathrm{l})+\mathrm{Y}_2(\mathrm{~g}) \leftrightharpoons 2 \mathrm{XY}(\mathrm{g})$, the $\Delta \mathrm{H}^0$ and $\Delta \mathrm{S}^0$ are $+29.3 \mathrm{~kJ} / \mathrm{mol}$ and $104.1 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ respectively at 298 K . Find the free energy change in $\mathrm{kJ} / \mathrm{mol}$.
COMEDK 2025 Morning Shift
9
Given that the standard enthalpy of combustion of $\mathrm{C}_{(\mathrm{S})}$ and $\mathrm{CS}_2(\mathrm{l})$ are -393.3 and $-1108.76 \mathrm{~kJ} / \mathrm{mol}$ respectively and the standard enthalpy of formation of $\mathrm{CS}_2$ is $128.02 \mathrm{~kJ} / \mathrm{mol}$. What is $\Delta H_f^0$ of $\mathrm{SO}_2$ ?
COMEDK 2025 Morning Shift
10

The Enthalpy of combustion of $$\mathrm{C}_6 \mathrm{H}_5 \mathrm{COOH}(\mathrm{s})$$ at $$25^{\circ} \mathrm{c}$$ and 1.0 atm pressure is $$-2546 \mathrm{~kJ} / \mathrm{mol}$$. What is the Internal energy change for this reaction?

COMEDK 2024 Evening Shift
11

Given :

$$ \begin{gathered} \Delta \mathrm{H}^0 \mathrm{f}_{\text {of }} \mathrm{CO}_2(\mathrm{~g})=-393.5 \mathrm{~kJ} / \mathrm{mol} \\ \Delta \mathrm{H}^0{ }_{\mathrm{f}} \text { of } \mathrm{H}_2 \mathrm{O}(\mathrm{l})=-286 \mathrm{~kJ} / \mathrm{mol} \\ \Delta \mathrm{H}^0{ }_{\mathrm{f}} \text { of } \mathrm{C}_3 \mathrm{H}_6(\mathrm{~g})=+20.6 \mathrm{~kJ} / \mathrm{mol} \end{gathered} $$

$$\Delta \mathrm{H}^0$$ isomerisation of Cyclopropane to Propene $$=-33 \mathrm{~kJ} / \mathrm{mol}$$

What is the standard enthalpy of combustion of Cyclopropane?

COMEDK 2024 Evening Shift
12

5.0 moles of an Ideal gas at 3.0 atm pressure and $$27^{\circ} \mathrm{C}$$ is compressed isothermally to half its volume by application of an external pressure of $$3.5 \mathrm{~atm}$$. What is the amount of work done (in joules) on the gas? Given: $$1 \mathrm{~L} \mathrm{~atm}=101.3 \mathrm{~J}: \mathrm{R}=0.082 \mathrm{~L} \mathrm{~atm} \mathrm{~K}{ }^{-1} \mathrm{~mol}^{-1}$$

COMEDK 2024 Evening Shift
13

The $$\Delta \mathrm{H}_{(\mathrm{f})}^{\mathrm{o}}$$ of $$\mathrm{NO}_2(\mathrm{~g})$$ and $$\mathrm{N}_2 \mathrm{O}_4(\mathrm{~g})$$ are 16.0 and $$4.0 \mathrm{k} \mathrm{cal} \mathrm{mol}^{-1}$$ respectively. The heat of dimerisation of $$\mathrm{NO}_2$$ in $$\mathrm{k}$$ cal is :

COMEDK 2024 Afternoon Shift
14

At Constant volume, the heat required to raise the temperature of $$4.48 \mathrm{~L}$$ of an ideal gas at STP by $$15^{\circ} \mathrm{C}$$ is 12.0 calories. The $$\mathrm{C_p}$$ of the gas is _____________ $$(\mathrm{R}=2 \mathrm{~Cal} \mathrm{~kg}^{-1} \mathrm{~mol}^{-1})$$

COMEDK 2024 Afternoon Shift
15

The correct option for free expansion of an ideal gas under adiabatic condition is:

COMEDK 2024 Afternoon Shift
16

The standard enthalpy of formation of $$\mathrm{CH}_4$$, the standard enthalpy of sublimation of Carbon and the bond dissociation enthalpy of Hydrogen gas are $$-74.8,+719.6$$ and $$436 \mathrm{~kJ} / \mathrm{mol}$$ respectively. What is the bond enthalpy of $$\mathrm{C}-\mathrm{H}$$ bond in Methane?

COMEDK 2024 Morning Shift
17

Given: $$\Delta \mathrm{G}^0{ }_{\mathrm{f}}$$ of $$\mathrm{C}_2 \mathrm{H}_2$$ is $$2.09 \times 10^5 \mathrm{~J} / \mathrm{mol}$$ and $$\Delta \mathrm{G}_{\mathrm{f}}^0$$ of $$\mathrm{C}_6 \mathrm{H}_6$$ is $$1.24 \times 10^5 \mathrm{~J} / \mathrm{mol}$$. Calculate the equilibrium constant for the cyclic polymerisation of Ethyne to Benzene at $$27^{\circ} \mathrm{C}$$. $$(\mathrm{R}=8.314 \mathrm{JK}^{-1} \mathrm{~mol}^{-1})$$

COMEDK 2024 Morning Shift
18

If the enthalpy of formation of a diatomic molecule $$\mathrm{AB}$$ is $$-400 \mathrm{~kJ} / \mathrm{mol}$$ and the bond dissociation energies of $$\mathrm{A}_2$$ and $$\mathrm{B}_2$$ and $$\mathrm{AB}$$ are in the ratio $$2: 1: 2$$, what is the bond dissociation enthalpy of $$\mathrm{B}_2$$ ?

COMEDK 2024 Morning Shift
19

If 2 moles of $$\mathrm{C}_6 \mathrm{H}_6(\mathrm{~g})$$ are completely burnt $$4100 \mathrm{~kJ}$$ of heat is liberated. If $$\Delta H^{\circ}$$ for $$\mathrm{CO}_2(\mathrm{~g})$$ and $$\mathrm{H}_2 \mathrm{O}(l)$$ are $$-410$$ and $$-285 \mathrm{~kJ}$$ per mole respectively then the heat of formation of $$\mathrm{C}_2 \mathrm{H}_6(g)$$ is

COMEDK 2023 Morning Shift
20

For an adiabatic change in a system, the condition which is applicable is

COMEDK 2023 Morning Shift
21

$$5.8 \mathrm{~g}$$ of a gas maintained at $$95^{\circ} \mathrm{C}$$ occupies the same volume as $$0.368 \mathrm{~g}$$ of hydrogen gas maintained at a temperature of $$17^{\circ} \mathrm{C}$$ and pressure being the same atmospheric pressure for both the gases. What is the molecular mass of the unknown gas?

COMEDK 2023 Evening Shift
22

Gaseous Nitrous oxide decomposes at $$298 \mathrm{~K}$$ to form Nitrogen gas and Oxygen gas. The $$\Delta \mathbf{H}$$ for the reaction at $$1.0 \mathrm{~atm}$$ pressure and $$298 \mathrm{~K}$$ is $$\mathbf{- 1 6 3 . 1 5} \mathbf{~ k J}$$. Calculate Internal energy change for the decomposition of $$100 \mathrm{~g}$$ of Nitrous oxide gas under the same conditions of temperature and pressure.

COMEDK 2023 Evening Shift
23

A Gas taken in a closed vessel is heated from $$54^{\circ} \mathrm{C}$$ to $$1254^{\circ} \mathrm{C}$$. The pressure of the gas becomes ___________ times its original pressure $$\mathrm{P_1}$$

COMEDK 2023 Evening Shift
24

Which of the following are not path functions?

I. H $$-$$ TS

II. W

III. q

IV. q + W

COMEDK 2022
25

The relation between work done in reversible and irreversible process is

COMEDK 2022
26

In which of the following changes, entropy decreases?

COMEDK 2022
27

The difference between heat capacity at constant pressure and heat capacity at constant volume is

COMEDK 2022
28

When the expansion of a gas occurs in vacuum and at constant volume, then

COMEDK 2021
29

The change in the energy of system if 500 cal of heat energy are added to a system and system does 350 cal of work on the surroundings will be

COMEDK 2021
30

Calculate the difference between C$$_p$$ and C$$_V$$ for 10 moles of an ideal gas

COMEDK 2021
31

The value of $$\Delta G^\circ$$ for the phosphorylation of glucose in glycolysis is 13.8 kJ/mol. The value of $$K_C$$ at 298 K is

COMEDK 2021
32

Which of the following is an intensive property?

COMEDK 2020
33

Thermodynamic standard conditions of temperature and pressure are

COMEDK 2020
34

In which of the following process, a maximum increase in entropy is observed?

COMEDK 2020
35

Consider the reaction,

C(s) + O$$_2$$(g) $$\rightarrow$$ CO$$_2$$(g) + 393.5 kJ

The signs of $$\Delta H,\Delta S$$ and $$\Delta G$$ respectively are

COMEDK 2020
36

Entropy of the universe is

COMEDK 2020
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