Thermodynamics Practice Questions
AP (Advanced Placement) · AP Chemistry · 149 free MCQs with instant results and detailed explanations.
149
Total
48
Easy
76
Medium
25
Hard
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Sample Questions from Thermodynamics
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Q1
Easy
Which of the following best describes the first law of thermodynamics?
A.
Energy cannot be created or destroyed, only transformed.
B.
The entropy of an isolated system always increases.
C.
Heat flows from cold to hot systems.
D.
Chemical reactions cannot absorb energy.
Show Answer & Explanation
Correct Answer: A
The first law of thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. This is a fundamental principle in thermodynamics.
Q2
Easy
At constant pressure, the heat added to a system is equal to which of the following?
A.
Change in enthalpy
B.
Change in internal energy
C.
Work done by the system
D.
Entropy change
Show Answer & Explanation
Correct Answer: A
At constant pressure, the heat added to a system corresponds to the change in enthalpy (ฮH). This is a key concept in thermodynamics related to processes occurring under constant pressure conditions.
Q3
Easy
What is the term for the energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius?
A.
Specific Heat Capacity
B.
Enthalpy
C.
Thermal Conductivity
D.
Calorimetry
Show Answer & Explanation
Correct Answer: A
Specific heat capacity is defined as the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. This makes option A the correct answer.
Q4
Medium
What is the change in enthalpy (ฮH) when 1 mole of water vapor at 100ยฐC condenses to liquid water at the same temperature? Assume that the enthalpy of vaporization of water is 40.7 kJ/mol.
A.
-40.7 kJ
B.
40.7 kJ
C.
0 kJ
D.
-80.0 kJ
Show Answer & Explanation
Correct Answer: A
When water vapor condenses, it releases energy equal to its enthalpy of vaporization. Thus, ฮH = -40.7 kJ.
Q5
Medium
Which of the following processes is endothermic?
A.
Dissolving ammonium nitrate in water
B.
Combustion of propane
C.
Condensation of steam
D.
Sublimation of dry ice
Show Answer & Explanation
Correct Answer: A
Dissolving ammonium nitrate in water absorbs heat from the surroundings, making it an endothermic process.
Q6
Medium
A gas expands isothermally and reversibly at a temperature of 300 K. If the initial volume is 2 L and the final volume is 6 L, what is the change in entropy (ฮS) for this process? (Assume R = 8.314 J/(molยทK) and 1 mole of gas)
A.
5.76 J/K
B.
6.17 J/K
C.
7.33 J/K
D.
8.00 J/K
Show Answer & Explanation
Correct Answer: B
For isothermal expansion, ฮS = nR ln(Vf/Vi). Here, ฮS = 1 mol * 8.314 J/(molยทK) * ln(6/2) = 6.17 J/K.
Q7
Medium
Which of the following statements about Gibbs free energy (G) is TRUE?
A.
G decreases for spontaneous processes.
B.
G is always positive for all reactions.
C.
G can never be zero in a spontaneous reaction.
D.
G is independent of temperature.
Show Answer & Explanation
Correct Answer: A
A decrease in Gibbs free energy (ฮG < 0) indicates that a process is spontaneous, confirming that G decreases for spontaneous processes.
Q8
Hard
A gas undergoes a cyclic process with the following steps: isothermal expansion at 300 K, adiabatic expansion, isothermal compression, and then adiabatic compression. If the work done by the gas during the entire cycle is 200 J, what is the net change in internal energy of the gas over one complete cycle?
A.
0 J
B.
100 J
C.
200 J
D.
400 J
Show Answer & Explanation
Correct Answer: A
In a complete cyclic process, the net change in internal energy is always zero because the system returns to its original state. Thus, despite the work done by the gas, the internal energy does not change, which makes option A the correct choice.
Q9
Hard
Which of the following statements accurately describes the effect of temperature on the entropy change of a system undergoing a spontaneous process?
A.
Entropy increases with temperature for all processes.
B.
Entropy decreases with increasing temperature for exothermic processes.
C.
Entropy increases with increasing temperature for endothermic processes.
D.
Entropy is independent of temperature changes.
Show Answer & Explanation
Correct Answer: C
In endothermic processes, heat is absorbed, and higher temperatures provide greater molecular motion, leading to an increase in entropy as disorder increases.
Q10
Hard
Calculate the change in Gibbs free energy (ฮG) at 298 K for the reaction: 2 H2(g) + O2(g) โ 2 H2O(g), given that ฮH = -241.8 kJ and ฮS = -188.8 J/K. Which of the following is the correct value of ฮG?
A.
-273.0 kJ
B.
-237.5 kJ
C.
-265.8 kJ
D.
-295.6 kJ
Show Answer & Explanation
Correct Answer: B
Using the Gibbs free energy equation ฮG = ฮH - TฮS, we convert ฮS to kJ (ฮS = -0.1888 kJ/K), then calculate ฮG = -241.8 kJ - (298 K * -0.1888 kJ/K) = -237.5 kJ.
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Thermodynamics โ AP (Advanced Placement) AP Chemistry Practice Questions Online
This page contains 149 practice MCQs for the chapter Thermodynamics in AP (Advanced Placement) AP Chemistry. The questions are organized by difficulty โ 48 easy, 76 medium, 25 hard โ so you can choose the right level for your preparation.
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