Thermodynamics Chapter-Wise Test 8

Correct answer Carries: 4.

Wrong Answer Carries: -1.

A system releases 500 J of heat and has 200 J of work done on it. What is the change in internal energy?

First Law: \( \Delta Q = \Delta U + \Delta W \). \( \Delta Q = -500 \, \text{J} \) (heat released), \( \Delta W = -200 \, \text{J} \) (work on system). \( -500 = \Delta U - 200 \Rightarrow \Delta U = -500 + 200 = -300 \, \text{J} \).

-350 J
-300 J
-250 J
-200 J
2

A system in a cyclic process absorbs \( 780 \, \text{J} \) of heat and rejects \( 300 \, \text{J} \). What is the net work done?

For cyclic: \( \Delta U = 0 \), \( Q_{\text{net}} = W \).

\( Q_{\text{net}} = Q_{\text{absorb}} - Q_{\text{reject}} = 780 - 300 = 480 \, \text{J} \).

\( W = 480 \, \text{J} \).

400 J
480 J
520 J
600 J
2

What is the change in internal energy for \( 0.3 \, \text{moles} \) of an ideal gas heated from \( 280 \, \text{K} \) to \( 340 \, \text{K} \) at constant volume? (\( C_v = 20.8 \, \text{J mol}^{-1} \text{K}^{-1} \))

\( \Delta U = \mu C_v \Delta T \).

\( \mu = 0.3 \), \( C_v = 20.8 \), \( \Delta T = 340 - 280 = 60 \).

\( \Delta U = 0.3 \times 20.8 \times 60 = 374.4 \, \text{J} \approx 374 \, \text{J} \).

350 J
374 J
400 J
450 J
2

0.25 kg of a substance at 30°C absorbs 1500 J of heat, reaching 60°C. What is its specific heat capacity?

Specific heat: \( s = \frac{\Delta Q}{m \Delta T} \). \( \Delta Q = 1500 \, \text{J} \), \( m = 0.25 \, \text{kg} \), \( \Delta T = 60 - 30 = 30 \, \text{K} \). \( s = \frac{1500}{0.25 \times 30} = 200 \, \text{J kg}^{-1} \text{K}^{-1} \).

150 J kg⁻¹ K⁻¹
200 J kg⁻¹ K⁻¹
250 J kg⁻¹ K⁻¹
300 J kg⁻¹ K⁻¹
2

How much heat is required to raise the temperature of \( 0.6 \, \text{kg} \) of copper from \( 20^\circ \text{C} \) to \( 50^\circ \text{C} \)? (Specific heat of copper = \( 386.4 \, \text{J kg}^{-1} \text{K}^{-1} \))

\( \Delta Q = m s \Delta T \).

\( m = 0.6 \), \( s = 386.4 \), \( \Delta T = 50 - 20 = 30 \).

\( \Delta Q = 0.6 \times 386.4 \times 30 = 6955.2 \, \text{J} \approx 6955 \, \text{J} \).

6700 J
6955 J
7100 J
7300 J
2

How much heat is required to raise the temperature of \( 0.35 \, \text{kg} \) of copper from \( 15^\circ \text{C} \) to \( 45^\circ \text{C} \)? (Specific heat of copper = \( 386.4 \, \text{J kg}^{-1} \text{K}^{-1} \))

\( \Delta Q = m s \Delta T \).

\( m = 0.35 \), \( s = 386.4 \), \( \Delta T = 45 - 15 = 30 \).

\( \Delta Q = 0.35 \times 386.4 \times 30 = 4057.2 \, \text{J} \approx 4057 \, \text{J} \).

3800 J
4057 J
4200 J
4400 J
2

What thermodynamic property ensures that \( \Delta U \) is zero in a cyclic process?

Internal energy (\( U \)) is a state function, meaning its value depends only on the state, not the path. In a cyclic process, returning to the initial state means \( \Delta U = 0 \), regardless of intermediate changes.

Path dependence
State function nature
Heat transfer
Work done
2

In an isobaric process, \( 1 \, \text{mole} \) of an ideal gas expands from \( 8 \, \text{L} \) to \( 16 \, \text{L} \) at \( 360 \, \text{K} \). What is the work done by the gas? (\( R = 8.3 \, \text{J mol}^{-1} \text{K}^{-1} \))

\( W = P \Delta V \), \( P V = \mu R T \).

\( \Delta V = 16 - 8 = 8 \, \text{L} \).

\( P = \frac{\mu R T}{V_1} = \frac{1 \times 8.3 \times 360}{8} = 373.5 \, \text{atm} \) (unit correction needed).

Directly: \( W = \mu R T \left(\frac{V_2 - V_1}{V_1}\right) \), but \( W = P \Delta V \).

\( W = 1 \times 8.3 \times 360 = 2988 \, \text{J} \) (adjusted for \( \Delta V \) in correct units).

2500 J
2988 J
3200 J
3500 J
2

Which law of thermodynamics introduces the concept of temperature as a physical quantity that is equal for systems in thermal equilibrium with a third system?

The Zeroth Law of Thermodynamics states that if two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This leads to the concept of temperature as a measurable property that is the same for systems in thermal equilibrium.

First Law
Second Law
Zeroth Law
Third Law
3

Which of the following statements is incorrect about reversible processes?

Reversible processes require quasi-static conditions and no dissipation, not common in nature where irreversibility dominates. Option C is incorrect.

They are quasi-static
They lack dissipative effects
They are common in nature
They can be reversed fully
3

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