Thermochemistry Practice Questions
SPM (Malaysia) · SPM Chemistry · 149 free MCQs with instant results and detailed explanations.
149
Total
46
Easy
77
Medium
26
Hard
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Sample Questions from Thermochemistry
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Q1
Easy
Which of the following statements best describes the concept of exothermic reactions?
A.
They absorb heat from the surroundings.
B.
They release heat to the surroundings.
C.
They require energy to start.
D.
They do not involve energy changes.
Show Answer & Explanation
Correct Answer: B
Exothermic reactions are characterized by the release of heat to the surroundings, leading to an increase in the temperature of the surroundings.
Q2
Easy
What is the effect of increasing the temperature on reaction rate according to the collision theory?
A.
It decreases the energy of collisions.
B.
It increases the frequency of collisions.
C.
It prevents effective collisions.
D.
It has no effect on the reaction rate.
Show Answer & Explanation
Correct Answer: B
According to collision theory, increasing the temperature increases the kinetic energy of the molecules, leading to more frequent and effective collisions, which increases the reaction rate.
Q3
Easy
What is the primary focus of thermochemistry?
A.
The study of the energy and heat changes in chemical reactions
B.
The analysis of chemical bonding and molecular structure
C.
The determination of atomic mass and periodicity
D.
The exploration of states of matter and phase transitions
Show Answer & Explanation
Correct Answer: A
Thermochemistry primarily focuses on the energy and heat changes that occur during chemical reactions, making option A the correct answer.
Q4
Medium
What is the enthalpy change of the reaction if 100 g of water is heated from 25Ā°C to 75Ā°C? (Specific heat capacity of water = 4.18 J/gĀ°C)
A.
20900 J
B.
4180 J
C.
1000 J
D.
2090 J
Show Answer & Explanation
Correct Answer: A
The enthalpy change is calculated using the formula q = m Ć c Ć ĪT. Here, m = 100 g, c = 4.18 J/gĀ°C, and ĪT = 75Ā°C - 25Ā°C = 50Ā°C. Therefore, q = 100 Ć 4.18 Ć 50 = 20900 J.
Q5
Medium
In an endothermic reaction, which of the following statements is true?
A.
Heat is released to the surroundings.
B.
The reaction absorbs heat from the surroundings.
C.
The enthalpy change is negative.
D.
The products have lower energy than reactants.
Show Answer & Explanation
Correct Answer: B
In endothermic reactions, heat is absorbed from the surroundings, resulting in a positive enthalpy change. Thus, option B is correct.
Q6
Medium
Which of the following processes has a negative change in enthalpy?
A.
Melting of ice
B.
Combustion of wood
C.
Dissolving ammonium nitrate in water
D.
Evaporation of water
Show Answer & Explanation
Correct Answer: B
The combustion of wood is an exothermic process, which releases heat into the surroundings, resulting in a negative change in enthalpy.
Q7
Medium
If the standard enthalpy change of formation of CO2 is -393.5 kJ/mol, what is the energy change when 2 moles of CO2 are formed?
A.
-393.5 kJ
B.
-787.0 kJ
C.
393.5 kJ
D.
787.0 kJ
Show Answer & Explanation
Correct Answer: B
For 2 moles of CO2, the total energy change is 2 Ć -393.5 kJ = -787.0 kJ, indicating an exothermic reaction.
Q8
Hard
What is the enthalpy change when 100 g of water at 25Ā°C is heated to 75Ā°C? (Specific heat capacity of water = 4.18 J/gĀ°C)
A.
20900 J
B.
2090 J
C.
4180 J
D.
8370 J
Show Answer & Explanation
Correct Answer: A
The enthalpy change can be calculated using the formula: q = m Ć c Ć ĪT. Here, m = 100 g, c = 4.18 J/gĀ°C, and ĪT = 75Ā°C - 25Ā°C = 50Ā°C. Thus, q = 100 g Ć 4.18 J/gĀ°C Ć 50Ā°C = 20900 J.
Q9
Hard
In an endothermic reaction, which of the following statements is true regarding the enthalpy change?
A.
The products have higher enthalpy than the reactants.
B.
The reactants have higher enthalpy than the products.
C.
Enthalpy change is zero.
D.
Enthalpy change is negative.
Show Answer & Explanation
Correct Answer: A
In an endothermic reaction, energy is absorbed from the surroundings, resulting in products that have higher energy (enthalpy) compared to the reactants. This indicates that the enthalpy change is positive.
Q10
Hard
The enthalpy change for the reaction 2H2(g) + O2(g) ā 2H2O(l) is -572 kJ. If you start with 4 moles of H2 and 2 moles of O2, how much energy is released when the reaction goes to completion?
A.
-572 kJ
B.
-1144 kJ
C.
-286 kJ
D.
-5720 kJ
Show Answer & Explanation
Correct Answer: B
The reaction releases 572 kJ for every 2 moles of H2 reacted. Starting with 4 moles doubles this energy release to -1144 kJ, as the amount of reactants is doubled.
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Thermochemistry ā SPM (Malaysia) SPM Chemistry Practice Questions Online
This page contains 149 practice MCQs for the chapter Thermochemistry in SPM (Malaysia) SPM Chemistry. The questions are organized by difficulty ā 46 easy, 77 medium, 26 hard ā so you can choose the right level for your preparation.
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