All Free Chemistry MCQs with Answers
Every Chemistry question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
13,720 questions · page 592 of 686
- A. A
- B. B
- C. C
- D. D
Explanation: Option C has been identified as the incorrect statement about enthalpy changes (∆H°).
Correct answer: C11822. Joule is the unit of:
- A. Force
- B. Work
- C. Power
- D. Velocity
Explanation: The erg is a unit of energy and work in the CGS system. One erg is equal to one dyne applied over a distance of one centimeter.
Correct answer: Work- A. Initial condition of the system
- B. Final condition of the system
- C. Path of the system
- D. Both initial and final condition of the system
Explanation: State functions provide valuable information about the thermodynamic state of a system, and they are used to describe and predict the…
Correct answer: Both initial and final condition of the system11824. Energy is absorbed:
- A. In bond breaking
- B. In endothermic reactions
- C. In bond formation
- D. Both A and B
Explanation: The correct answer is "Both A and B." Both bond breaking and endothermic reactions involve the absorption of energy from the surroundings.
Correct answer: Both A and B- A. Chemical equilibrium
- B. Chemical bonding
- C. Heat contents of a compound
- D. All of these
Explanation: Thermochemistry provides information about the heat contents of compounds, especially in the context of chemical reactions.
Correct answer: Heat contents of a compound- A. Avogadro's law
- B. Gas laws
- C. Hess's law
- D. Faraday's law
Explanation: There are many compounds, for which ∆H cannot be measured directly by calorimetric method.
Correct answer: Hess's law- A. Thermochemistry is the study of relation between heat energy and chemical reactions
- B. An exothermic reaction is one which is accompanied by evolution of heat
- C. An endothermic reaction is one in which heat is absorbed
- D. Energy needed to raise the temperature of substance by 1°C is specific heat.
Explanation: The false statement is Energy needed to raise the temperature of a substance by 1°C is specific heat.
Correct answer: Energy needed to raise the temperature of substance by 1°C is specific heat.- A. Initial and final enthalpy change of reaction
- B. Different intermediate reactions
- C. State of reactants and products
- D. Nature of reactants and products
Explanation: Option B is correct because enthalpy is a state function. So, enthalpy change does not depend upon the different steps involved in the…
Correct answer: Different intermediate reactions- A. Heat energy
- B. Heat of hydration
- C. Lattice energy
- D. Heat of solution
Explanation: The Born-Haber cycle is a theoretical model that allows us to calculate the lattice energy of ionic compounds.
Correct answer: Lattice energy- A. It is an endothermic process
- B. It can be represented as H3O+(aq)+ OH-(aq) → 2H2O(l)
- C. The enthalpy change per mole of H2O formed is independent of the acid or alkali used as they are strong
- D. Both B and C
Explanation: The correct answer is C. The standard enthalpy change of neutralization is approximately -57.4 kJmol-1 for the reaction of strong acids…
Correct answer: The enthalpy change per mole of H2O formed is independent of the acid or alkali used as they are strong- A. A: Remains constant
- B. B: Decreases
- C. C: Increases
- D. D: Remains unchanged
Explanation: Option B is correct because in an endothermic reaction, heat is absorbed from the surroundings, resulting in a decrease in the temperature…
Correct answer: B: Decreases- A. Release of energy
- B. Absorption of energy
- C. No change in energy
- D. Sharing of nucleus
Explanation: During bond formation, energy is released as atoms achieve a more stable, lower-energy state.
Correct answer: Release of energy- A. 15 kJ/mol
- B. -17 kJ/mol
- C. 16.2 kJ/mol
- D. -16.5 kJ/mol
Explanation: The enthalpy of solution (∆Hosol) of ammonium chloride (NH4Cl) is +16.2 kJ/mol.
Correct answer: 16.2 kJ/mol- A. Translational energy only
- B. All kinds of kinetic energy
- C. Elastic potential energy only
- D. All of these
Explanation: Internal energy is the total of all types of energy present within a system.
Correct answer: All of these- A. Fusion
- B. Vaporization
- C. Sublimation
Explanation: Sublimation is a phase transition in which a substance changes directly from a solid to a gas without passing through the liquid phase.
Correct answer: Sublimation- A. Exothermic reactions
- B. Decomposition reactions
- C. Dissociation reactions
- D. Endothermic reactions
Explanation: In exothermic reactions, the system releases heat to the surroundings, causing the enthalpy change (∆H) to be negative.
Correct answer: Exothermic reactions- A. -676 kJ mol-1
- B. -110 kJ mol-1
- C. 110 kJ mol-1
- D. 676 kJ mol-1
Explanation: To find the enthalpy change for the combustion of graphite to form CO, apply Hess's Law by using the given reactions.
Correct answer: -110 kJ mol-1- A. Vibrational energy
- B. Rotational energy
- C. Translational energy
- D. Rnergy due to gravitation
Explanation: The correct answer is gravitational energy.Internal energy is the total energy of a system, including the kinetic energy and potential…
Correct answer: Rnergy due to gravitation- A. ∆H = 0
- B. ∆H > ∆E
- C. ∆H = ∆E
- D. ∆H < ∆E
Explanation: For the reaction 2 NH3 ➞ N2 + 3 H2, the correct statement is that ∆H = ∆E.
Correct answer: ∆H = ∆E- A. It is an endothermic process
- B. Formation of water is a spontaneous process
- C. It is the heat evolved for complete reaction of 2 moles of oxygen with excess of hydrogen
- D. Water is at lower energy than its reactants
Explanation: The correct answer is that water is at lower energy than its reactants.
Correct answer: Water is at lower energy than its reactants