Thermodynamics Test

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Thermodynamics Test - 59

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Weekly Quiz Competition

Question 1
1 / -0

Consider the process on a system shown in fig. During the process, the work done by the system

A
Continuously increases

B
Continuously decreases

C
`First increases then decreases

D
First decreases then increases

Solution

In this given figure,
The work done first decreases then increases
$$\therefore$$ Option $$D$$ is correct answer.
Question 2
1 / -0

during an experiment an ideal gas obeys an addition equation of state $${p^2}V$$ constant . The initial temperature and pressure of gas are $$T$$ and $$V$$ respectively. When it expends to volume $$2V.$$ then its temperature will be:

A
$$T$$

B
$$\sqrt 2 \,T$$

C
$$2 T$$

D
$$2\sqrt 2 \,T$$

Solution

Given: $$P^2V= constant$$, initial temperature and volume are $$ T $$ and $$V$$ respectively.
Solution:
Let initial pressure be $$P_1$$ and final pressure be $$P_2$$
Final volume is $$2V$$
Initial temperature be $$T$$ and final temperature be $$T_2$$
From ideal gas equation, $$PV=RT$$ let n=1
$$P=\dfrac{RT}{V}$$ and $$P^2V= constant$$
$$\therefore V(\dfrac{RT}{V}^2)constant$$
$$\Rightarrow \dfrac {T^2}{V}= constant$$
$$\Rightarrow \dfrac{T_2^2}{2V^2}=\dfrac{T^2}{V^2}$$
$$\therefore T_2=\sqrt2 T$$
Hence the correct option is B.
Question 3
1 / -0

In which of the following sets, all the properties belongs to same category (all extensive or all intensive)?

A
Mass, volume, pressure

B
Temperature, pressure,volume

C
Heat capacity, density, entropy

D
Enthalpy, internal energy volume

Solution

Solution:
1. Extensive properties are the properties which depends on size of the system. Some of the examples are mass, volume, enthalpy, internal energy, entropy etc.
2. Intensive properties are those which does not depend on the size of the system.For example, Pressure, temperature, density etc.
Hence the correct option is D.
Question 4
1 / -0

One end of metal bar of area of cross section $$5cm^2$$ and $$25cm$$ in length is in stream and other end is in contact with ice. The amount of ice melts in one minute is :
$$(L=80cal/gm,K=0.8 \ cgs\ units)$$

A
$$16gm$$

B
$$12gm$$

C
$$24gm$$

D
$$36gm$$

Solution

Given,

$$K=0.8 cgs$$ unit

$$L=80 cal/gm$$

$$A=5cm^2$$

$$l=25 cm$$

$$dT=100^0$$

$$t=1min=60 sec$$

Rate of flow of heat,

$$q=\dfrac{Q}{t}=KA\dfrac{dT}{dx}$$. . . . .(1)

We know that, $$Q=mL$$

equation (1) becomes,

$$\dfrac{mL}{t}=KA\dfrac{dT}{dx}$$

$$\dfrac{80m}{60}=0.8\times 5\times \dfrac{100}{25}$$

$$m=12gm$$

The correct option is B.
Question 5
1 / -0

The work done for the cycle shown in given figure, will be :

A
$$45 J$$

B
$$54 J$$

C
$$22.5 J$$

D
$$32.5 J$$

Solution

The work done for the cycle is equal to the area under the $$P-V$$ curve .
The work done, $$W=\dfrac{1}{2}\times cb\times ac$$
$$W=\dfrac{1}{2}\times (5-2)\times (50-20)$$
$$W=\dfrac{1}{2}\times 3\times 30$$
$$W=45J$$
The correct option is B.
Question 6
1 / -0

An ideal gas $$\left ( \gamma =3/2 \right )$$ is expanded adiabatically. If V is the original volume, for what final volume, the RMS speed become $$\dfrac{v_{rms}}{2}$$?

A
$$\dfrac{v\times 9}{2}$$

B
16v

C
8v

D
$$\dfrac{v\times 16}{9}$$

Solution
Question 7
1 / -0

Energy of activation of an exothermic reaction is

A
Zero

B
Negative

C
Positve

D
Cannot be predicted

Solution
Question 8
1 / -0

For V versus T curves at constant pressure $$p_{1}$$ and $$p_{2}$$ for an ideal gas
shown in figure-

A
$$P_{1} > P_{2}$$

B
$$P_{1} < P_{2}$$

C
$$P_{1} = P_{2}$$

D
$$P_{1} \ge P_{2}$$

Solution
Question 9
1 / -0

Following figure shows P-T graph for four processes A, B, C and D. Select the corret alternative.

A
$$A-$$ isobaric process

B
$$B-$$ Adiabatic process

C
$$C-$$ isochoric process

D
$$D-$$ isothermal process

Solution
Question 10
1 / -0

One mole of an ideal gas undergoes a thermodynamic cyclic process as shown in the figure. The cyclic process consists of an isochoric, an isothermal and an adiabatic process. Adiabatic exponent of gas is

A
1.5

B
$$\dfrac{ln 5}{ln 3} $$

C
1.25

D
$$\dfrac{ln 6}{ln 3} $$

Solution