Thermodynamics Test

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Thermodynamics Test - 42

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following can be calculated from Born-Haber cycle for $$Al_2O_3$$?

A
Lattice energy of $$Al_2O_3$$

B
Electron affinity of O-atom

C
Ionisation energy of Al

D
All of these

Solution

The Born-Haber Cycle can be applied to determine the lattice energy of an ionic solid; ionization energy, electron affinity, dissociation energy, sublimation energy, heat of formation, and Hess's Law.
Question 2
1 / -0

A constant volume gas thermometer shows pressure reading of 50 cm and 90 cm of mercury at 0$$^{0}C$$ and 100$$^{0}C$$ respectively. When the pressure reading is 60 cm of mercury, the temperature is:-

A
25$$^{0}C$$

B
40$$^{0}C$$

C
$$^{0}C$$

D
$$30^{0}C$$

Solution

Given,

Temperature $${{T}_{1}}={{0}^{o}}C$$ and height $${{h}_{1}}=50\,cm$$

Temperature$${{T}_{2}}=100{{\,}^{o}}C$$ and height $${{h}_{2}}=90\,cm$$

$$ \dfrac{T-{{T}_{1}}}{h-{{h}_{1}}}=\dfrac{{{T}_{2}}-{{T}_{1}}}{{{h}_{2}}-{{h}_{1}}} $$

$$ \dfrac{T-0}{60-50}=\dfrac{100-0}{90-50} $$

$$ T=25{{\,}^{o}}C $$

Hence, at $$60 cm $$, temperature is $$25{{\,}^{o}}C$$
Question 3
1 / -0

A vessel contains $$N$$ molecules of a gas at temperature $$T$$. Now the number of molecules is doubled, keeping the total energy in the vessel constant. The temperature of the gas is.

A
$$T$$

B
$$2T$$

C
$$\dfrac{T}{2}$$

D
$$\sqrt 2 T$$

Solution

Total energy$$=nkT$$
$$n'=2n$$ (Since the 'P' is in closed box)
$$T'=\cfrac { T }{ 2 } $$
$$PV=nRT$$
$$\therefore T'=\cfrac { T }{ 2 } $$
Question 4
1 / -0

If the temperature difference $$T_1 - T_2$$ is $$120^oC$$. the temperature difference between points A & B is

A
30

B
45

C
60

D
75

Solution
Question 5
1 / -0

When 250 KJ heat is the system then it does work of 400 KJ then calculate change in internal energy of system ?

A
650 KJ

B
-650 KJ

C
200 KJ

D
-200 KJ

Solution
Question 6
1 / -0

1 g of a steam at $$100^{_-^0}C$$ melt how much ice at $$0^{_-^0}C$$? (Latent heat of ice = 80 cal/gm and latent heat of steam = 540 cal/gm)-

A
1 gm

B
2 gm

C
4 gm

D
8 gm

Solution

Suppose $$m$$ gm ice melted,
then heat required for its melting = $$mL=m×80cal$$.
heat avaiable with steam for being condensed and then brought to $$0^∘C.$$
$$=1×540+1×1×(100-0)=640cal$$
⇒ heat lost = heat taken
⇒$$640=m×80⇒m=8gm$$.
Question 7
1 / -0

One gram of ice (at $$0^{o}C$$) is mixed with one gram of steam (at $$100^{o}C$$). After thermal equilibrium, the temperature of the mixture is

A
$$0^{o}C$$

B
$$100^{o}C$$

C
$$55^{o}C$$

D
$$80^{o}C$$

Solution

Total steam does not condense
$$\therefore$$ Final temperature $$={ 100 }^{ 0 }C$$
Question 8
1 / -0

Internal energy of an ideal gas depends on:

A
pressure

B
temperature

C
volume

D
none of these

Solution

The relation between the internal energy and enthalpy, it can be derived that the internal energy of the gas is independent of the volume and pressure whereas it is only temperature-dependent.
Option $$B$$ is correct.
Question 9
1 / -0

Calculate $${ \Delta }_{ r }G$$ for the reaction at $$2\mathring { 7\quad } C$$ :-
$${ H }_{ 2(g) }+2A{ g }_{ (aq) }^{ + }\rightleftharpoons 2A{ g }_{ s }+2{ H }_{ (aq)}^{+} $$
Given : $${ P }_{ { H }_{ 2 } }=0.5$$ bar; $${ [A{ g }^{ + }] }=1{ 0 }^{ -5 }M$$
$${ [{ H }^{ + }] }=1{ 0 }^{ -3 }M$$ ;
$${ \triangle }_{ r }\mathring { G\quad \quad } [A{ g }^{ + }]=77.1\quad KJ/mol$$

A
-154.2 KJ/mol

B
-178.9 KJ/mol

C
-129.5 KJ/mol

D
none of these

Solution
Question 10
1 / -0

What is the change in entropy when $$2.5 $$ mole of water is heated from $$27^{o}C$$ to $$87^{o}C$$? Assume that the heat capacity is constant $$(C_{p.m}(H_{2}O)=4.2\ J/g-K\ In (1.2)=0.18)$$

A
$$16.6\ J/K$$

B
$$9\ J/K$$

C
$$34.02\ J/K$$

D
$$1.89\ J/K$$

Solution