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 507 of 686
- A. More CO2 and H2 are produced to compensate for temperature change
- B. The reaction will move in backward direction for compensation
- C. No change will take place
- D. The reaction will stop
Explanation: When heat is applied to a system at equilibrium, Le Chatelier's principle states that the system will adjust to counteract the change and…
Correct answer: The reaction will move in backward direction for compensation- A. I only
- B. II only
- C. Both (I) and (II) are correct
- D. Neither (I) nor (II) are correct
Explanation: In the open beaker, H₂ gas is produced, and work is done by the system against the constant atmospheric pressure (W = -ΔngRT).
Correct answer: Both (I) and (II) are correct- A. -98 kJ/mol
- B. 98 kJ/mol
- C. 14 kJ/mol
- D. 24 kJ/mol
Explanation: The neutralization of a weak acid releases less heat because some energy is used to dissociate the acid first.
Correct answer: 14 kJ/mol- A. -40 kJ/mol
- B. +33 kJ/mol
- C. -45 kJ/mol
- D. -6 kJ/mol
Explanation: The standard enthalpy of formation (ΔH°) of nitrogen dioxide (NO₂) is a known endothermic value.
Correct answer: +33 kJ/mol- A. - 342 kJ/mol
- B. - 234 kJ/mol
- C. - 346 kJ/mol
- D. - 178 kJ/mol
Explanation: The neutralization reaction is H⁺(aq) + OH⁻(aq) → H₂O(l). The enthalpy change is ΔHneut = ΔHf (H₂O) - [ΔHf (H⁺) + ΔHf (OH⁻)].
Correct answer: - 234 kJ/mol- A. 100 gm
- B. 180 gm
- C. 200 gm
- D. 120 gm
Explanation: First, calculate the work done: W = mgh = 100 kg × 10 m/s² × 500 m = 500,000 J.
Correct answer: 120 gm- A. Boiling point
- B. Molarity
- C. Freezing point
- D. All
Explanation: An intensive property is a property of a system that does not depend on the amount of substance.
Correct answer: All- A. 58 gm
- B. 56 g
- C. 54 g
- D. 52 g
Explanation: First, calculate the heat required to warm the water: Q = mcΔT = (10,000 g)(1 cal/g°C)(70°C) = 700,000 cal = 700 kcal.
Correct answer: 58 gm- A. 4q3 − q1 − 2q2
- B. q1 + q2 − q3
- C. q1 + 2q2 − 4q3
- D. q1 + 4q2 − 4q3
Explanation: The enthalpy of formation is calculated as the energy required to break bonds minus the energy released from forming bonds.
Correct answer: q1 + 2q2 − 4q3- A. -1.91
- B. +2.1
- C. -2.1
- D. +1.9
Explanation: Here, we can use the equation: ΔH (graphite → diamond) = ΔH (graphite → CO₂) - ΔH (diamond → CO₂) ΔH = -393.51 kJ mol⁻¹ - (-395.41 kJ…
Correct answer: +1.9- A. -228.88 KJ/mol
- B. -343.52 KJ/mol
- C. +228.88 KJ/mol
- D. -22.88 KJ/mol
Explanation: For the formation of H⁺ ions from hydrogen and O₂⁻ ions from oxygen, the standard enthalpy of formation at 25°C is -228.88 KJ/mol.
Correct answer: -228.88 KJ/mol- A. A
- B. B
- C. C
- D. D
Explanation: N₂(g) + O₂(g) → 2NO(g) is endothermic, meaning it absorbs heat from its surroundings (it has a positive ΔH value, around +180.6 kJ/mol).
Correct answer: C10133. What is the Gibbs free energy change for a reaction at 298 K if ΔH = -50 kJ and ΔS = -150 J/K?
- A. -5.3 kJ
- B. -44.7 kJ
- C. +5.3 kJ
- D. +44.7 kJ
Explanation: ΔG = ΔH - TΔS = -50000 - 298 × (-150) = -50000 + 44700 = -5300 J = -5.3 kJ.
Correct answer: -5.3 kJ- A. -67800 cal
- B. -67650.4 cal
- C. -67762.5 cal
- D. -54.6 cal
Explanation: Calculate ΔCp (Change in Heat Capacity): Reaction: CO(g) + 1/2 O2(g) → CO2(g). ΔCp = Cp(Products) - ΣCp(Reactants).
Correct answer: -67800 cal- A. Always less than lattice energy
- B. Same as lattice energy
- C. Always greater than lattice energy
- D. May or may not be same as lattice energy
Explanation: Enthalpy of formation (ΔHf) includes lattice energy (LE) plus the additional enthalpy changes needed to form ions from their elements…
Correct answer: Always greater than lattice energy- A. Heat of reaction
- B. Spontaneity of reaction
- C. Rate of reaction
- D. Entropy of reaction
Explanation: Thermodynamics describes the energy changes directly whereas entropy changes and spontaneity of a reaction are explained through derived…
Correct answer: Rate of reaction- A. Remain constant
- B. Increase
- C. Either increase or decrease
- D. Decrease
Explanation: An endothermic reaction absorbs heat from its surroundings to proceed. If the reaction is rapid, it will quickly draw heat from the…
Correct answer: Decrease- A. Evaporation
- B. Sublimation
- C. Respiration
- D. Boiling
Explanation: Respiration is the metabolic process where organisms break down glucose and oxygen to produce carbon dioxide, water, and energy.
Correct answer: Respiration- A. Isothermal process
- B. Spontaneous
- C. Non-spontaneous
- D. Adiabatic process
Explanation: A spontaneous process is a process that occurs in a system without the need for external energy input.
Correct answer: Spontaneous- A. Its value gives an idea about the relative stability of reactants and the products
- B. It is always negative
- C. Its value depends upon the nature of bonds
- D. Its value may be negative or positive
Explanation: The enthalpy of formation (ΔHf ) can be either negative (exothermic, for stable compounds) or positive (endothermic, for unstable…
Correct answer: It is always negative