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 512 of 686
- 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: Enthalpy10225. One Calorie is equal to:
- 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 J10226. Which of the following values of heat of formation indicates that the product is least stable?
- 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)10234. Work done on the system is
- 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- A. Total heat
- B. Volume
- C. Entropy
- D. Internal energy
Explanation: In an isochoric process, also known as an isovolumetric or constant volume process, the volume of the system remains constant throughout…
Correct answer: Volume