All Free Chemistry MCQs with Answers

• A. Increase in enthalpy
• B. Decrease in enthalpy
• C. No change in enthalpy
• D. Decrease in internal energy

Explanation: When a solid melts and transforms into a liquid, it requires an input of energy to break the intermolecular forces and allow the particles…

• A. Heat of combustion
• B. Heat of decomposition
• C. Heat of solution
• D. Heat of reaction

Explanation: The correct option is D) Heat of reaction. The ∆Hf (enthalpy of formation) of a compound is equal in magnitude to the heat of reaction.

• A. High
• B. Low
• C. Zero
• D. One

Explanation: Based on the usual behavior of heat of solution for common ionic compounds like NaCl, the correct option is B) Low.

• A. Internal energy
• B. Temperature of a body
• C. Kinetic energy
• D. Heat energy

Explanation: Thermal energy also called heat energy is produced when a rise in temperature causes atoms and molecules to move faster and collide with…

• A. Law of mass action
• B. Law of conservation of energy
• C. Law of conservation of mass
• D. Dalton's law of partial pressure

Explanation: Hess's law is based on the principle of the conservation of energy. It states that the total enthalpy change of a chemical reaction is…

• A. Heat lost by the system
• B. Work done on the system
• C. Work done by the system
• D. Positive ∆E when heat is lost by the system

Explanation: Work done on the system is positive. When work is done on the system, it means that energy is being transferred into the system.

• A. Exothermic process
• B. Endothermic process
• C. Neutral
• D. Energy wasted

Explanation: When an electron is removed from an atom, it requires an input of energy to overcome the electrostatic attraction between the electron and…

• A. Endothermic reactions
• B. Exothermic reactions
• C. Endergonic reactions
• D. Heat gaining reactions

Explanation: Exothermic reactions are the reactions that release heat to their surroundings, causing the surroundings to warm up while the system loses…

• A. 4.98 J
• B. 7.98 J
• C. 4.18 J
• D. 8.21 J

Explanation: One calorie is approximately equal to 4.18 joules. This conversion factor is used to convert energy measurements between the calorie…

• A. 1st law
• B. 2nd law
• C. 3rd law
• D. None of these

Explanation: The first law of thermodynamics, also known as the Law of Energy Conservation, states that energy cannot be created or destroyed; it can…

• A. Electrochemistry
• B. Biochemistry
• C. Thermochemistry
• D. Analytical chemistry

Explanation: The study of chemical reactions involving change in heat energy is called thermochemistry.

• A. -60.5 KJ/mol
• B. -46.5 KJ/mol
• C. -70.5 KJ/mol
• D. -57.4KJ/mol

Explanation: The enthalpy of neutralization when one mole of strong base reacts with one mole of strong acid is approximately -57.1 kJ/mol.

• A. Hess's law
• B. Carnot cycle
• C. Born Haber cycle
• D. Haber's process

Explanation: The enthalpy cycle used to calculate the lattice energy is called the Born-Haber cycle.The Born-Haber cycle is a thermochemical cycle that…

• A. Enthalpy of formation
• B. Enthalpy of neutralization
• C. Enthalpy of sublimation
• D. Enthalpy of reaction

Explanation: The change in enthalpy for the reaction NaOH + HCl → NaCl + H2O is called the enthalpy of neutralization.The enthalpy of neutralization is…

• A. Heat
• B. Work
• C. Heat & work
• D. Force

Explanation: Heat is the transfer of thermal energy between a system and its surroundings due to a temperature difference.

• A. Microscopic
• B. Dependent
• C. Macroscopic
• D. Constant

Explanation: A state function is a macroscopic property of a system. It is a property that depends only on the current state of the system and not on…

• A. Exothermic reaction
• B. Endothermic reaction
• C. Spontaneous reaction
• D. Non-spontaneous reaction

Explanation: An exothermic reaction releases heat energy into its surroundings. During combustion, substances typically release heat, making the heat…

• A. Solid phase
• B. Gases phase
• C. Liquids, solids and solution
• D. None of these

Explanation: In many cases involving reactions in liquids, solids, or solutions, the differences between ΔH and ΔE are relatively small.

• A. Thermal energy
• B. Total heat content
• C. Internal energy
• D. Enthalpy

Explanation: The sum of all the energies present in a reaction mixture or system is called the "internal energy" (U).

• A. Internal Energy
• B. Enthalpy
• C. Work
• D. None of these

Explanation: Work is not a state function. In thermodynamics, a state function is a property whose value depends only on the current state of a system…