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 516 of 686
- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: Standard enthalpy of atomization is the enthalpy change that occurs when one mole of a sample is dissociated into its atoms under standard…
Correct answer: Option C- A. Exothermic reactions
- B. Decomposition reactions
- C. Dissociation reaction
- D. Endothermic reactions
Explanation: In exothermic reactions, heat is released to the surroundings as a product.
Correct answer: Exothermic reactions- A. Remains unchanged
- B. Increases
- C. Increases than decreases
- D. Decreases
Explanation: The enthalpy of atomization is the enthalpy change that accompanies the total separation of all atoms in a chemical substance.
Correct answer: Decreases10304. What will be the enthalpy change in the reaction given below?2H2 + O2→ 2H2O ∆H = +205.5 kJ mol-1
- A. 205.5 kJ/mol
- B. Zero kJ/mol
- C. -205.5 kJ/mol
- D. 1 kJ/mol
Explanation: This is a trick question. Most students choose A however that is wrong.
Correct answer: -205.5 kJ/mol- A. -394 kJ/mol
- B. +394 kJ/mol
- C. -294 kJ/mol
- D. -390 kJ/mol
Explanation: The heat of formation (∆Hf°) for carbon dioxide (CO2) is: ∆Hf° = -394 kj/molThe negative sign indicates that the formation of one moleucle…
Correct answer: -394 kJ/mol- A. Exothermic reactions
- B. Endothermic reactions
- C. Photochemical reactions
- D. Non-spontaneous reactions
Explanation: In exothermic reactions, the energy of the reactants is higher than that of the products.
Correct answer: Exothermic reactions- A. Heat is evolved
- B. Heat is absorbed
- C. Heat may be evolved or absorbed
- D. Electrolyte does not dissolve in water
Explanation: A solution is a homogeneous mixture of two or more substances and can either be in the gas phase, the liquid phase, or the solid phase.
Correct answer: Heat may be evolved or absorbed- A. Increase in boiling point of liquid and decrease in melting point of solid
- B. Increase in both boiling and melting points
- C. Decrease in boiling point of liquid and increase in melting point of solid
- D. Decrease in both boiling and melting points
Explanation: Whenever a soluble, non-volatile impurity is added to a liquid, some of the solute particles tend to migrate toward the surface of the…
Correct answer: Increase in boiling point of liquid and decrease in melting point of solid- A. China dish
- B. Burner
- C. Laboratory
- D. 𝐶𝑎𝐶𝑂3
Explanation: The system is the collective substances in the reaction such as the reactants and products.
Correct answer: 𝐶𝑎𝐶𝑂3- A. Dissolution
- B. Crystallization
- C. Bond breaking
- D. Condensation
Explanation: The process of dissolving can be endothermic (temperature goes down) or exothermic (temperature goes up).
Correct answer: Dissolution- A. 436Kj/mol
- B. 40.7 Kj/mol
- C. 272 Kj/mol
- D. 436÷Avagadros no Kj/mol
Explanation: Bond energy is the amount of energy required to break one mole of covalent bonds in a gaseous molecule, resulting in separate gaseous…
Correct answer: 436Kj/mol- A. CaCl2
- B. K2O
- C. CaO
- D. BaCl2
Explanation: CaO has higher lattice energy because the lattice energy increases when the charge on the atom increases.
Correct answer: CaO- A. △H= qw
- B. △E=q - P△V
- C. △H=q+w
- D. △E = q+W
Explanation: The first law of thermodynamics states that the change in internal energy (△E) of a system is equal to the heat (q) added to the system…
Correct answer: △E=q - P△V10314. The amount of energy required to break one mole of a particular type of bond is equal to its:
- A. Activation energy
- B. Ionization energy
- C. Bond Energy
- D. Potential energy
Explanation: Bond energy is the amount of energy required to break one mole of a particular type of bond in a molecule or compound.
Correct answer: Bond Energy- A. △H = 213 kcal/mole
- B. △H = 231 kcal/mole
- C. △H = 426 kcal/mole
- D. △H = 312 kcal/mole
Explanation: The enthalpy of combustion of methane (CH4) is -890 kJ/mol. To convert this to kilocalories, use the conversion factor 1 kJ = 0.239 kcal.
Correct answer: △H = 213 kcal/mole- A. ∆E=q+W
- B. ∆E=-q+W
- C. ∆E=-q-W
- D. ∆E=q-W
Explanation: The expression for 1st law of thermodynamics is ΔE = q-w STB Pg- 157
Correct answer: ∆E=q+W- A. ∆E - P∆V
- B. ∆E + P∆V
- C. -∆E + P∆V
- D. -∆E - P∆V
Explanation: ΔH is known as change in enthalpy which is the sum of internal energy and work done. Hence, ΔH = ΔE + PΔVSo, option B is correct.
Correct answer: ∆E + P∆V- A. Low temperature
- B. High pressure
- C. Continuous removal of NH3
- D. Continuous addition of NH3
Explanation: In the Haber's process, ammonia is synthesized from nitrogen and hydrogen gases.
Correct answer: Continuous addition of NH3- A. Zero
- B. Positive
- C. Negative
- D. Constant
Explanation: In an exothermic reaction, heat is released, so the enthalpy change (ΔH°) is negative.
Correct answer: Negative- A. Average translational kinetic energy
- B. Average rotational kinetic energy
- C. Average translational potential energy
- D. Average vibrational kinetic energy
Explanation: Heat flow between hotter and colder gases continues until all the molecules have an equal average translational kinetic energy due to the…
Correct answer: Average translational kinetic energy