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 15 of 37
- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: Since it is an endothermic process it takes heat from the surrounding making the temperature fall below room temperature.
Correct answer: Option B- A. Total energy of the system and surroundings is conserved
- B. Energy can neither be created nor destroyed
- C. The first law is synonymous with the law of conservation of energy
- D. Total energy of the system is increasing
Explanation: The first law of thermodynamics, also known as the law of conservation of energy, asserts that the total energy within an isolated system…
Correct answer: Total energy of the system is increasing- A. Hess's law
- B. Henry's law
- C. Kirchoff's law
- D. Clapeyron equation '
- E. Boyle's law
Explanation: Hess's Law of Constant Heat Summation (or just Hess's Law) states that regardless of the multiple stages or steps of a reaction, the total…
Correct answer: Hess's law- A. Equilibrium
- B. Constant
- C. Low
- D. High
Explanation: The activation energy of a chemical reaction is closely related to its rate.
Correct answer: High- A. Enthalpy
- B. Internal energy
- C. Heat capacity
- D. work done
Explanation: Enthalpy is defined as the sum of the internal energy of a system and the product of its pressure and volume.
Correct answer: Enthalpy- A. 4.18 kJ
- B. 4.18 J
- C. 0.418 KJ mol-1
- D. 0.418 KJ
Explanation: 1 calorie equals 4.18 J. It is very often confused with 1 kcal, which equals to 4.18 kJ
Correct answer: 4.18 J- A. - 94 kcal
- B. + 21.4 kcal
- C. - 231 kcal
- D. + 64.8 kcal
Explanation: In the context of heat of formation (ΔH), a negative value indicates that the formation of the compound is exothermic, meaning the…
Correct answer: + 64.8 kcal- A. －20.75 kJ
- B. -2075 kJ
- C. Zero
- D. －20.75 x 373/273 kJ
Explanation: As it is provided in the given statement that heat capacities of reactants and products are the same, therefore there will be no energy…
Correct answer: －20.75 kJ- A. Amount of reactants
- B. Pressure of reaction
- C. Physical state of reactants and products
- D. Temperature
Explanation: The correct answer is Pressure of reaction. Enthalpy is a thermodynamic state function that represents the heat content of a system.
Correct answer: Pressure of reaction- A. 43 KJ/mole
- B. 37 KJ/mole
- C. 25 KJ/mole
- D. 19 KJ/mole
Explanation: Threshold E = activation E + normal E of reactant 31 = A + 12 A = 31 - 12 = 19 kJ/mol
Correct answer: 19 KJ/mole- A. A liquid into its vapours at its boiling point
- B. Liquids into its vapours
- C. Solids into vapours
- D. Solid into liquid at its melting point
Explanation: Molar heat of vapourization refers to the conversion of one mole of a liquid to its vapors at a constant temperature, which is the boiling…
Correct answer: A liquid into its vapours at its boiling point- A. Isomorphs
- B. Polymorphs
- C. Amorphous solids
- D. Crystalline solids
Explanation: 'Amorphous solids' do not possess any particular heat of fusion thus Option C is correct.'Crystalline solids' consist of atoms, ions, and…
Correct answer: Amorphous solids- A. 0 K
- B. -400 K
- C. -210 K
- D. -273.15 K
Explanation: A change of one kelvin is the same amount of temperature change as one degree Celsius, but the Kelvin scale is "absolute" in the sense…
Correct answer: 0 K- A. C(s) + 1/2 O2 -> CO(g)
- B. C(g) + 1/2 O2 -> CO(g)
- C. C(s) + O(g) -> CO(g)
- D. C(g) + CO2 (g) -> 2CO(g)
Explanation: Since we are talking about the enthalpy of formation, we must ensure that the product has only one mole and the reactants are in their…
Correct answer: C(s) + 1/2 O2 -> CO(g)- A. Negative
- B. depends upon Boundary Conditions
- C. Positive
- D. Zero
Explanation: Work done on the system is positive in chemistry and negative in physics.Similarly work done by the system is negative in chemistry and…
Correct answer: Positive- A. Pseudotherm
- B. Isotherm
- C. Biotherm
- D. All of these
Explanation: If a graph is outlined in between pressure on the x-axis (abscissa) and volume on the y-axis (ordinate), then a curve is obtained.
Correct answer: Isotherm- A. Conduction
- B. Convection
- C. Radiation
- D. All of these
Explanation: Heat always flows from a region of higher temperature to a region of lower temperature. It flows by conduction, convection, and radiation.
Correct answer: All of these- A. Positive
- B. Negative
- C. Zero
- D. Neither positive nor negative
Explanation: Endothermic reactions are described as reactions involving an increase in energy levels of the product.
Correct answer: Positive- A. Pressure
- B. Volume
- C. Temperature
- D. All of these
Explanation: A bomb calorimeter is a type of 'constant-volume calorimeter' used in measuring the heat of combustion of a particular reaction.
Correct answer: Volume- A. CCl4
- B. O3
- C. CO
- D. C
Explanation: The heat of formation of carbon monoxide is difficult to determine because carbon tends to form carbon dioxide when burned in oxygen.
Correct answer: CO