Free Enthalpy MCQs with Answers
45 Enthalpy MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Enthalpy is the heat content of a system measured at constant pressure, and its change indicates whether a reaction or physical process is endothermic or exothermic. The topic covers state functions, enthalpy diagrams, standard enthalpy of formation, combustion and neutralisation, and the relationship between ΔH and internal energy change.
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45 questions · page 2 of 3
- A. Heat of combustion
- B. Heat of formation
- C. Heat of solution
- D. Heat of dilution
Explanation: The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of…
Correct answer: Heat of formation22. The change in heat energy in a chemical reaction at constant temperature and pressure is called:
- A. Enthalpy change
- B. Heat of sublimation
- C. Internal energy change
- D. Heat of formation
Explanation: The change in heat energy in a chemical reaction at constant temperature and pressure is called enthalpy change.
Correct answer: Enthalpy change23. What is the value of enthalpy of neutralization when one mole of base reacts with one mole of acid?
- A. -60.5 kJ/mol
- B. -46.5kJ/mol
- C. -70.5 kJ/mol
- D. -57.4kJ/mol
Explanation: Option A: This option suggests a value of -60.5 kJ/mol for the enthalpy of neutralization.
Correct answer: -57.4kJ/mol- A. Neutralization
- B. Combustion
- C. Atomization
- D. All of these
Explanation: Atomization is the process of breaking all the bonds in a substance to form individual gaseous atoms.
Correct answer: Atomization- A. ∆H = qv + w
- B. ∆H = E + PV
- C. ∆H = qp + PV
- D. ∆H = E
Explanation: In symbols, the enthalpy, H, equals the sum of the internal energy, E, and the product of the pressure, P, and volume, V, of the system: H…
Correct answer: ∆H = E + PV- A. 300 K and 2 atm
- B. 300 K and 1atm
- C. 298 K and 1 atm
- D. 295 K and 1 atm
Explanation: Enthalpy is measured at standard conditions i.e. 298 K and 1 atm.
Correct answer: 298 K and 1 atm- A. Volume
- B. Pressure
- C. Temperature
- D. Mass
Explanation: At a constant pressure, the heat flow for any process is equal to the change in the internal energy of the system plus the work done (PV).
Correct answer: Pressure- A. ∆H is always less than ∆U
- B. ∆H is always greater than ∆U
- C. ∆H is less than ∆U if the number of moles of gaseous products is greater than the number of moles of gaseous reactants.
- D. ∆H is less than ∆U if the number of moles of gaseous products is less than the number of moles of gaseous reactants.
Explanation: The relationship is ΔH = ΔU + ΔngRT. If the number of moles of gas decreases during the reaction, Δng is negative.
Correct answer: ∆H is less than ∆U if the number of moles of gaseous products is less than the number of moles of gaseous reactants.- A. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
- B. 2CH4(g) + 4O2(g) → 2CO2(g) + 4H2O(g)
- C. CH4(s) + 2O2(g) → CO2(g) + 2H2O(g)
- D. CH4(l) + 2O2(g) → CO2(g) + 2H2O(g)
Explanation: The standard enthalpy of combustion is defined for the combustion of one mole of a substance in its standard state.
Correct answer: CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)- A. Enthalpy of formation
- B. Enthalpy of neutralization
- C. Enthalpy of solution
- D. Enthalpy of combustion
Explanation: Enthalpy of formation, enthalpy of neutralization and enthalpy of solution can be determined by glass calorimeter.
Correct answer: Enthalpy of combustion- A. The reaction proceeds in the forward direction at 300 K
- B. At 1200 K, reaction proceeds in the reverse direction
- C. At 300 K, Kp > 1
- D. At 300 K, the products will be favoured more than reactants at equilibrium
Explanation: This is the following solution: kp is less than one, reaction is non spontaneous for sponataneous reactions kp is greater than one
Correct answer: At 300 K, Kp > 1- A. H+ (aq) + OH-(aq) -> H2O(l)
- B. H2 (g) + ½ O2 (g) -> H2O (l)
- C. H2O(g) + H2O(l)
- D. H2O(s) -> H2O(l)
Explanation: The reaction H₂(g) +1/2 O₂(g) → H₂O(l) shows the standard enthalpy change for the formation of water, where △H is the heat of formation of…
Correct answer: H2 (g) + ½ O2 (g) -> H2O (l)- A. Enthalpy of atomization
- B. Enthalpy of fusion
- C. Enthalpy of vaporization
- D. Enthalpy of formation
Explanation: Option A, enthalpy of atomization, is the energy required to completely separate all the atoms in a chemical substance.
Correct answer: Enthalpy of atomization- A. Heat of fusion
- B. Heat of vapourization
- C. Heat of sublimation
- D. Heat of evaporation
Explanation: The heat of fusion is the enthalpy change required to melt one mole of a solid substance at its melting point The heat of vaporization is…
Correct answer: Heat of sublimation- A. Enthalpy of formation
- B. Enthalpy of combustion
- C. Enthalpy of neutralization
- D. Enthalpy of sublimation
Explanation: The enthalpy of formation is the standard reaction enthalpy for the formation of the compound from its elements (atoms or molecules) in…
Correct answer: Enthalpy of formation- A. Enthalpy of combustion
- B. Enthalpy of solution.
- C. Enthalpy of formation
- D. Enthalpy of atomization
Explanation: Combustion reactions release heat, so the enthalpy change of the system, H, will always be negative.
Correct answer: Enthalpy of combustion- A. ΔG
- B. ΔH
- C. ΔE
- D. ΔH-ΔE
Explanation: Enthalpy change is the heat absorbed by a substance at constant pressure. ΔH= ΔU + PΔV= Q - PΔV + PΔV = Q
Correct answer: ΔH- A. Solid phase
- B. Liquid phase
- C. Gaseous phase
- D. Plasma phase
Explanation: ∆n is equal to the total moles of gas on the products side - total moles of gas on the Reactant side.
Correct answer: Gaseous phase- A. ΔHv
- B. ΔHf
- C. ΔHi
- D. ΔHs
Explanation: The molar heat of fusion (ΔHfus) of a substance is the heat absorbed by one mole of that substance as it is converted from a solid to a…
Correct answer: ΔHf- A. MgCO3 + 2HCl → MgCl2 + CO2 + H2O
- B. KOH + HCl → KCl + H2P
- C. NH4Cl + NaOH → NaCl + H2O + NH3
- D. H2SO4 + Mg(OH)2 → MgSO4 + 2H2O
Explanation: The given reaction depicts a neutralization reaction, where one mole of acid is neutralized by one mole of alkali (as indicated by 1 mole…
Correct answer: H2SO4 + Mg(OH)2 → MgSO4 + 2H2O