Free Thermochemistry and Energetics of Chemical Reactions MCQs with Answers
728 Thermochemistry and Energetics of Chemical Reactions MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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728 questions · page 28 of 37
541. By definition, the standard heat of formation of C2H6(g) is the enthalpy change for the reaction:
- A. 2C(s) + 6H(g) ---> C2H6(g)
- B. 2C(g) + 6H(g) ---> C2H6(g)
- C. 2C(s) + 3H2(g) ---> C2H6(g)
- D. 2C2H4(s) + H2(g) ---> C2H6(g)
Explanation: Standard enthalpy of formation is the heat of formation when one mole of a substance is formed from its elements in their standard state…
Correct answer: 2C(s) + 3H2(g) ---> C2H6(g)- 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 CO2547. 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)- 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