Thermodynamics Test

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Thermodynamics Test - 41

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Weekly Quiz Competition

Question 1
1 / -0

Under which of the following conditions is the relation, $$\Delta H=\Delta E+P\Delta V$$ valid for a system:

A
Constant pressure

B
Constant temperature

C
Constant temperature and pressure

D
Constant temperature, pressure and composition

Solution
Question 2
1 / -0

The heat capacity of 2.0 moles of He gas at constant temperature is (in cal/mol/K)

A
0

B
3

C
8

D
$$\infty $$

Solution
Question 3
1 / -0

For the reaction, $$2A(g)+B(g)\rightarrow 2D(g),\Delta {U}^{o}=-10.5kJ$$ and $$\Delta {S}^{o}=-44.10J{K}^{-1}$$. Calculate $$\Delta {G}^{o}$$ for the reaction and predict whether the reaction may occur spontaneously:

A
$$0.165\ kJ$$, the reaction is not spontaneous.

B
$$0.225\ kJ$$, the reaction is not spontaneous.

C
$$0.164\ kJ$$, the reaction is spontaneous.

D
$$0.225\ kJ$$, the reaction is spontaneous.

Solution
Question 4
1 / -0

Evaporation of water is

A
An endothermic change

B
An exothermic change

C
A process where no heat change occurs

D
A process accompained by chemical reaction

Solution

Evaporation is the process by which water changes from a liquid to a gas or vapor. This is a endothermic changr
Question 5
1 / -0

At $$27C$$ the reaction,
$${ C }_{ 6 }{ { H }_{ 6 } }_{ { (l) } }+\frac { 15 }{ 2 } { { O }_{ 2 } }_{ (g) }\rightarrow { { 6CO }_{ 2 } }_{ (g) }+{ { 3H }_{ 2 }O }_{ (l) }$$
proceeds spontaneously because the magnitude of?

A
$$\Delta H=T\Delta S$$

B
$$\Delta H>T\Delta S$$

C
$$\Delta H$$<$$T\Delta S$$

D
None of these

Solution

$$\Delta{H} < T \Delta{S}$$
As we know that,
$$\Delta{G} = \Delta{H} - T \Delta{S}$$
As the reaction is proceeding spontaneously, $$\Delta{G}$$ must be negative.
Therefore, for $$\Delta{G}$$ to be negative,
$$\Delta{H} < T \Delta{S}$$
Question 6
1 / -0

For the given reaction
$$H_{2}(g)+S(s)\longrightarrow H_{2}S(g);\ \Delta H_{T}=100\ kJ/mol$$ and $$\Delta S_{T}=400\ J/mol/K$$
Temperature at which above reaction occurs reversibly is (Assuming $$\Delta H_{T}$$ and $$\Delta S_{T}$$ are independent of temperature)

A
$$200\ K$$

B
$$250\ K$$

C
$$400\ K$$

D
$$None$$

Solution

We know that
$$\Delta S_T=\cfrac {\Delta H_T}{T}$$
Given, $$\Delta S_T= 400Jmol^{-1}K^{-1}$$
$$\Delta H_T= 100 KJmol^{-1}$$
So $$T= \cfrac {\Delta H_T}{\Delta S_T}= \cfrac {100 \times 1000}{400}=250K$$
Hence, Temperature is $$250K$$ .
Question 7
1 / -0

A gas occupies $$2L$$ at S.T.P. It is provided with $$300 Joule$$ of heat so that its volume becomes $$2.5 litre$$ at a pressure of $$1 atm$$. The value of $$\Delta U$$(Change in internal energy) of process is :-

A
$$350.5 Joule$$

B
$$249.5 Joule$$

C
$$150.35 Joule$$

D
None of these

Solution

Given:
Initial volume of gas,$$V_i =2 l$$
Heat provided, Q= 300J
Final volume, $$V_f = 2.5 l$$
Final pressure,$$P_f =1 atm$$

Solution:
We know that the work is done at constant pressure and thus is irreversible.
Work done, W=-P(Change in volume)
$$\Rightarrow W=-1×(2.5-2)$$
$$\Rightarrow W= -0.5 atm-l $$
$$\Rightarrow W= -0.5 ×101325 ×\dfrac{1}{1000} J$$
$$\Rightarrow W=-50.6625 J $$
From the first law of thermodynamics,
$$ Q=\delta U -W$$, where$$\delta U = Change in internal energy$$
$$\Rightarrow \delta U = Q+ W$$
$$\Rightarrow \delta U = 300 +(-50.6625) $$
Therfore, $$\delta U = 249.3Joule$$
Hence, correct option is B.
Question 8
1 / -0

In an isobaric process ratio of heat supplied to the system, to workdone by the system for diatomic gas is:

A
1:1

B
7:2

C
7:5

D
5:7

Solution

For isobaric process & $$n=1\,mol$$
$$dQ = \frac{5}{2}\,RdT + RdT = \frac{7}{2}RdT$$
$$\&\ dw = RdT$$
$$Ratio \to \frac{{dQ}}{{dw}} = \frac{{\frac{7}{2}RdT}}{{RdT}} = 7:2$$

Hence the answer is (B)
Question 9
1 / -0

The values of $$\Delta H$$ and $$\Delta S$$ for the reaction, $${ C }_{ \left( graphite \right) }+{ CO }_{ { 2 }_{ \left( g \right) } }\longrightarrow { 2CO }_{ \left( g \right) }$$ are $$170 \ kJ$$ and $$170 \ JK^{-1}$$, respectively. This reaction will be spontaneous at :-

A
$$510 \ K$$

B
$$710 \ K$$

C
$$910 \ K$$

D
$$1110 \ K$$

Solution
Question 10
1 / -0

Which of the polymer has the weakest intermolecular force of attraction?

A
$$\text{Nylon-6,6}$$

B
$$\text{Polyvinyl chloride}$$

C
$$\text{Cellulose}$$

D
$$\text{Natural Rubber}$$

Solution

Nylon and cellulose both have intermolecular bonding and polyvinyl chloride has dipole-dipole interaction. Whereas natural rubber is an elastomer. The weakest intermolecular forces are present in Elastomers. The irregular geometry of the molecules involves weak Van der Waals force of attraction.

Hence. option $$D$$ is correct.