Thermodynamics and Thermochemistry Practice Questions
JEE · Chemistry · 1545 free MCQs with instant results and detailed explanations.
1545
Total
367
Easy
709
Medium
469
Hard
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Topics in Thermodynamics and Thermochemistry
Hess's Law
320
Bond Energy
410
Gibbs Energy
402
Spontaneity
413
Sample Questions from Thermodynamics and Thermochemistry
Here are 10 sample questions. Start a quiz to get randomized questions with scoring.
Q1
Easy
Which of the following statements best describes Hess's Law?
A.
The total heat change in a reaction is independent of the path taken.
B.
Heat change is directly proportional to the concentration of reactants.
C.
The heat of formation is always negative for exothermic reactions.
D.
Heat change depends solely on the initial temperature of reactants.
Show Answer & Explanation
Correct Answer: A
Hess's Law states that the total heat change during a chemical reaction is independent of the route taken, as long as the initial and final conditions are the same.
Q2
Easy
If reaction A → B has an enthalpy change of -100 kJ/mol and reaction B → C has an enthalpy change of -50 kJ/mol, what is the enthalpy change for the overall reaction A → C according to Hess's Law?
A.
-150 kJ/mol
B.
-50 kJ/mol
C.
-100 kJ/mol
D.
0 kJ/mol
Show Answer & Explanation
Correct Answer: A
According to Hess's Law, the overall enthalpy change is the sum of the enthalpy changes of the individual reactions: -100 kJ/mol + (-50 kJ/mol) = -150 kJ/mol.
Q3
Easy
Which of the following enthalpy changes can be determined using Hess's Law?
A.
Enthalpy of combustion
B.
Enthalpy of fusion
C.
Enthalpy of vaporization
D.
All of the above
Show Answer & Explanation
Correct Answer: D
Hess's Law can be applied to calculate any enthalpy change, including those of combustion, fusion, and vaporization, as they all involve heat changes regardless of the pathway.
Q4
Medium
Which of the following statements best describes Hess's Law?
A.
The total enthalpy change is the sum of the enthalpy changes for each step.
B.
The enthalpy change is independent of the nature of the reactants.
C.
The enthalpy change varies with pressure and temperature.
D.
The enthalpy change is always negative for exothermic reactions.
Show Answer & Explanation
Correct Answer: A
Hess's Law states that the total enthalpy change for a reaction is the sum of the enthalpy changes for each individual step, regardless of the path taken.
Q5
Medium
If the enthalpy of formation of CO2 is -393.5 kJ/mol and of H2O is -285.8 kJ/mol, what is the enthalpy change for the combustion of methane (CH4)?
A.
-890.3 kJ/mol
B.
-802.5 kJ/mol
C.
-756.2 kJ/mol
D.
-1200.0 kJ/mol
Show Answer & Explanation
Correct Answer: A
Using Hess's Law, the combustion of methane is CH4 + 2O2 → CO2 + 2H2O. The enthalpy change = ΔHf (products) - ΔHf (reactants).
Q6
Medium
Which of the following reactions is an example of Hess's Law in action?
A.
Combining hydrogen and oxygen to form water.
B.
Dissolving salt in water.
C.
Breaking down glucose into carbon dioxide and water.
D.
Burning wood in a fire.
Show Answer & Explanation
Correct Answer: C
The breakdown of glucose can occur through multiple steps, and the total enthalpy change will be the same regardless of the path taken.
Q7
Medium
Given the enthalpy changes of three reactions, how can you find the enthalpy change for the overall reaction?
A.
By averaging the enthalpy changes.
B.
By adding the enthalpy changes algebraically, considering their signs.
C.
By multiplying the enthalpy changes.
D.
By taking the maximum value of the enthalpy changes.
Show Answer & Explanation
Correct Answer: B
The overall enthalpy change is obtained by adding the enthalpy changes of individual reactions while considering their respective signs (exothermic or endothermic).
Q8
Hard
A reaction A → B has an enthalpy change of +50 kJ/mol. If the reverse reaction B → A is carried out, what is the enthalpy change?
A.
-50 kJ/mol
B.
+50 kJ/mol
C.
0 kJ/mol
D.
+100 kJ/mol
Show Answer & Explanation
Correct Answer: A
According to Hess's Law, the enthalpy change for a reaction is equal in magnitude but opposite in sign for the reverse reaction.
Q9
Hard
Using Hess's Law, if reaction 1 has an enthalpy change of -100 kJ, and reaction 2 has +150 kJ, what is the enthalpy change if both reactions occur in sequence, leading to a net reaction that combines both?
A.
+50 kJ
B.
-50 kJ
C.
0 kJ
D.
+100 kJ
Show Answer & Explanation
Correct Answer: A
The total enthalpy change is the sum of individual changes: -100 kJ + 150 kJ = +50 kJ.
Q10
Hard
If the enthalpy of formation of CO2 is -393.5 kJ/mol, and for H2O is -285.8 kJ/mol, what is the enthalpy change for the combustion of glucose (C6H12O6) if it produces 6 CO2 and 6 H2O?
A.
-2800 kJ
B.
-1500 kJ
C.
-2000 kJ
D.
-1800 kJ
Show Answer & Explanation
Correct Answer: A
Use Hess's law to sum the enthalpy changes based on the products formed: ΔH = 6(-393.5) + 6(-285.8).
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Thermodynamics and Thermochemistry — JEE Chemistry Practice Questions Online
This page contains 1545 practice MCQs for the chapter Thermodynamics and Thermochemistry in JEE Chemistry. The questions are organized by difficulty — 367 easy, 709 medium, 469 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit. This chapter covers 4 topics, giving you comprehensive coverage of the entire chapter.