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 525 of 686
- A. Energy of activation
- B. Enthalpy of reaction
- C. Internal energy change
- D. Change in temperature
Explanation: Energy of activation is the minimum amount of energy reactants must have to form products.
Correct answer: Energy of activation- A. Na(s) + Cl2(g)➞NaCI ∆H= -787KJ/mol
- B. Na(s) + Cl2(g)➞ 2NaCI ∆H= -787KJ/mol
- C. 2Na(s) + Cl2(g)➞NaCI ∆H= -787KJ/mol
- D. Na(s) + 1/2Cl2(g)➞NaCI ∆H= -411KJ/mol
Explanation: Enthalpy change of formation states that it is the change in energy when 1 mole of a compound is formed from its element in their standard…
Correct answer: Na(s) + 1/2Cl2(g)➞NaCI ∆H= -411KJ/mol- A. -393.7
- B. -602
- C. -285.7
- D. -474.7
Explanation: Fact:The enthalpy change of formation of MgO is -602 kJ/mol.
Correct answer: -602- A. Remains constant
- B. Increases
- C. Decreases
- D. Remains unchanged
Explanation: During exothermic reactions, heat is released into surrondings as a result the temperature of surrounding air will increase.
Correct answer: Increases- A. Standard heat of formation of CO
- B. Standard heat of combustion of CO2
- C. Standard heat of combustion of CO
- D. Standard heat of combustion of C
Explanation: It is the standard enthalpy of combustion as 1 mole of carbon is burned under excess oxygen to form CO2.
Correct answer: Standard heat of combustion of CO210486. Which equation represents the change corresponding to the enthalpy change of atomisation of Iodine?
- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: Enthalpy change of atomisation is when 1 mole of gaseous atom is formed from its element in their standard state under standard…
Correct answer: Option A- A. Endothermic
- B. Exothermic
- C. Reversible
- D. Irreversible
Explanation: Irreversible reactions can proceed in one direction only. The products of the reaction cannot be converted back into the reactants without…
Correct answer: Irreversible- A. initial and final enthalpy change of reaction
- B. state of reactants and products
- C. diffrent intermediate reactions
- D. nature of reactant and products
Explanation: Enthalpy change of a reaction is a state function. Its value is dependant on the initial and final values of the system.
Correct answer: diffrent intermediate reactions- A. I.E, of sodium
- B. ∆H, of sodium
- C. ∆H°at of sodium + 1st I.E, of sodium
- D. I.E, of sodium + ∆H of sodium
Explanation: The above equation shows that sodium atom in its solid state has converted to sodium atom in its gaseous state, therefore, enthalpy change…
Correct answer: ∆H°at of sodium + 1st I.E, of sodium- A. Ostwald's law
- B. Hess' law
- C. Joule's principle
- D. 1st law of thermodynamics
Explanation: The statement stated above is the defintion of Hess' Law.
Correct answer: Hess' law- A. product is more than that of reactants
- B. reactant is more than that of products
- C. reactants and products remains equal
- D. All are correct
Explanation: In an exothermic recation, heat energy is released when products are formed. ΔH of an exothermic recation is always negative.
Correct answer: reactant is more than that of products- A. Only new bonds are being made
- B. bonds being made are stronger than bonds broken
- C. Only existing bonds are being broken
- D. bonds being broken are stronger than bonds made
Explanation: An exothermic reaction gives out heat energy. In an exothermic reaction, the energy absorbed during bond-making is greater than the energy…
Correct answer: bonds being made are stronger than bonds broken- A. C(diamond) + O2(g) → CO2(g)
- B. H2(g)+F2(g)2HF(g)
- C. N2(g) + 3H2(g)2NH3(g)
- D. CO(g) + O2(g) → CO2(g)
Explanation: The definition of ∆H is the heat of formation of a compound. It is the amount of heat that is released or absorbed when 1 mole of a…
Correct answer: C(diamond) + O2(g) → CO2(g)10494. If a gas absorbs 200kJ energy and consumes 100 kJ to do work. Increase in internal energy is:
- A. .-200 kJ
- B. -100 kJ
- C. +100 kJ
- D. +300 KJ
Explanation: The increase in internal energy is +100 kJ.In this case, the gas absorbs 200 kJ of heat and does 100 kJ of work.
Correct answer: +100 kJ- A. Pressure
- B. Volume
- C. Temperature
- D. None
Explanation: Pressure is constant In glass calorimeter .
Correct answer: Pressure- A. heat evolution
- B. heat absorption
- C. work done
- D. all of these
Explanation: Heat and work are two fundamental ways of energy transfer to and from the system.The energy changes in a chemical reaction can take place…
Correct answer: all of these- A. endothermic
- B. fast
- C. Exothermic
- D. cyclic
Explanation: The gaseous system will be regarded as cyclic.A cyclic process is a process that starts and ends at the same state.
Correct answer: cyclic- A. q depends only on the initial and final state
- B. E depends only on the initial and final state
- C. w depends only on initial and final state
- D. E depends upon path adopted to state go from A to B.
Explanation: The internal energy of a system is a state function, which means that it depends only on the initial and final state of the system.
Correct answer: E depends only on the initial and final state- A. vibrational energy
- B. rotational energy
- C. translational energy
- D. energy 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: energy due to gravitation- A. q= ∆E+W
- B. ∆E q-w
- C. ∆E = q+w
- D. ∆H = ∆E + P∆V
Explanation: The correct depiction of enthalpy is ∆H = ∆E + P∆V.
Correct answer: ∆H = ∆E + P∆V