Thermochemistry is the branch of chemistry that deals with

Heat changes accompanying chemical reactions

An isolated system is one that exchanges

Neither matter nor energy with surroundings

Thermochemistry MCQs 2026

15 questions with detailed answers · 7 from past papers · 2 quiz batches available

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Page 1 of 1 Questions 1–10 of 15

Q1 easy

Thermochemistry is the branch of chemistry that deals with
1. A Rates of chemical reactions
2. B Structure of atoms
3. C Heat changes accompanying chemical reactions
4. D Acid-base titrations
💡 Explanation:
Thermochemistry specifically studies the heat absorbed or released during chemical processes.
Q2 Past Paper · PPSC/FPSC/NTS easy

A system that can exchange both matter and energy with its surroundings is called
1. A Closed system
2. B Open system
3. C Isolated system
4. D Adiabatic system
💡 Explanation:
An open system freely exchanges both matter and energy with its surroundings.
Q3 Past Paper · PPSC/FPSC/NTS easy

A system that can exchange energy but not matter with its surroundings is called
1. A Open system
2. B Isolated system
3. C Closed system
4. D Homogeneous system
💡 Explanation:
A closed system allows energy transfer but keeps matter contained within its boundary.
Q4 easy

An isolated system is one that exchanges
1. A Neither matter nor energy with surroundings
2. B Only matter with surroundings
3. C Only energy with surroundings
4. D Both matter and energy freely
💡 Explanation:
An isolated system is completely sealed off, exchanging neither matter nor energy.
Q5 Past Paper · PPSC/FPSC/NTS easy

A reaction that releases heat to the surroundings is called
1. A Exothermic
2. B Endothermic
3. C Isothermal
4. D Adiabatic
💡 Explanation:
Exothermic reactions release heat energy to their surroundings.
Q6 easy

A reaction that absorbs heat from the surroundings is called
1. A Exothermic
2. B Isothermal
3. C Isochoric
4. D Endothermic
💡 Explanation:
Endothermic reactions absorb heat energy from their surroundings.
Q7 Past Paper · PPSC/FPSC/NTS easy

In an exothermic reaction, the enthalpy change (ΔH) is
1. A Zero
2. B Positive
3. C Infinite
4. D Negative
💡 Explanation:
Exothermic reactions release energy, giving them a negative enthalpy change by convention.
Q8 easy

In an endothermic reaction, the enthalpy change (ΔH) is
1. A Negative
2. B Positive
3. C Zero
4. D Undefined
💡 Explanation:
Endothermic reactions absorb energy, giving them a positive enthalpy change.
Q9 Past Paper · PPSC/FPSC/NTS easy

The first law of thermodynamics is essentially a statement of the law of conservation of
1. A Mass
2. B Momentum
3. C Charge
4. D Energy
💡 Explanation:
The first law states energy can neither be created nor destroyed, only transformed.
Q10 easy

According to the first law of thermodynamics, ΔU (change in internal energy) equals
1. A q - w only when w=0
2. B q + w (heat added plus work done on the system)
3. C w - q
4. D q × w
💡 Explanation:
The first law is expressed as ΔU = q + w, combining heat and work done on the system.
Q11 medium

Standard enthalpy of formation refers to the enthalpy change when 1 mole of a compound forms from its elements in their
1. A Standard states
2. B Molten states
3. C Gaseous states only
4. D Ionic forms
💡 Explanation:
Standard formation enthalpy uses elements in their most stable standard states at given conditions.
Q12 Past Paper · PPSC/FPSC/NTS medium

The standard enthalpy of formation of an element in its most stable state is defined as
1. A Zero
2. B One
3. C Negative
4. D Infinite
💡 Explanation:
By convention, elements in their standard reference state have zero enthalpy of formation.
Q13 medium

Hess's law states that the total enthalpy change of a reaction is
1. A Dependent on the reaction pathway
2. B Always zero
3. C Independent of the pathway, depending only on initial and final states
4. D Only valid for exothermic reactions
💡 Explanation:
Hess's law states enthalpy change depends only on initial and final states, not the path taken.
Q14 Past Paper · PPSC/FPSC/NTS medium

Hess's law is a consequence of which fundamental law
1. A Law of mass action
2. B Le Chatelier's principle
3. C Law of conservation of energy
4. D Law of multiple proportions
💡 Explanation:
Since enthalpy is a state function, Hess's law follows directly from energy conservation.
Q15 medium

Calorimetry is the technique used to measure
1. A Heat changes in physical and chemical processes
2. B Rate of reaction
3. C pH of a solution
4. D Molar mass of a gas
💡 Explanation:
Calorimetry experimentally measures the heat absorbed or released during a process.

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Thermochemistry MCQs 2026

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