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Enthalpy Change Δh MDCAT MCQs with Answers

Welcome to the Enthalpy Change Δh MDCAT MCQs with Answers. In this post, we have shared Enthalpy Change Δh Multiple Choice Questions and Answers for PMC MDCAT 2024. Each question in MDCAT Chemistry offers a chance to enhance your knowledge regarding Enthalpy Change Δh MCQs in this MDCAT Online Test.

Enthalpy change (ΔH) is defined as:
a) The heat content of a system
b) The difference between the heat absorbed and released
c) The heat absorbed or released at constant pressure
d) The change in volume of a system

Answer
c) The heat absorbed or released at constant pressure

For an exothermic reaction, ΔH is:
a) Positive
b) Negative
c) Zero
d) Variable

Answer
b) Negative

The enthalpy change for a reaction at constant pressure is represented by:
a) ΔH
b) ΔS
c) ΔG
d) ΔU

Answer
a) ΔH

If ΔH for a reaction is +25 kJ/mol, the reaction is:
a) Endothermic
b) Exothermic
c) Isothermal
d) Isobaric

Answer
a) Endothermic

Hess’s Law states that:
a) The enthalpy change is the same regardless of the number of steps in a reaction
b) Enthalpy change is not dependent on the path taken
c) The total enthalpy change for a reaction is the sum of enthalpy changes for individual steps
d) Enthalpy change is equal to the change in entropy

Answer
c) The total enthalpy change for a reaction is the sum of enthalpy changes for individual steps

The standard enthalpy change of formation (ΔH_f°) is:
a) The enthalpy change when one mole of a substance is formed from its elements in their standard states
b) The heat released during the combustion of one mole of a substance
c) The enthalpy change for a reaction at constant volume
d) The heat absorbed when one mole of a substance dissolves

Answer
a) The enthalpy change when one mole of a substance is formed from its elements in their standard states

The enthalpy change of combustion is:
a) The heat absorbed when one mole of a substance reacts with oxygen
b) The heat released when one mole of a substance is burned completely in oxygen
c) The enthalpy change for a phase transition
d) The heat absorbed during dissolution

Answer
b) The heat released when one mole of a substance is burned completely in oxygen

The enthalpy change associated with a phase transition is known as:
a) Enthalpy of fusion
b) Enthalpy of vaporization
c) Enthalpy of formation
d) Enthalpy of combustion

Answer
a) Enthalpy of fusion

The enthalpy of vaporization is:
a) The heat absorbed when a liquid turns into a gas
b) The heat released when a gas turns into a liquid
c) The heat absorbed when a solid turns into a liquid
d) The heat released during combustion

Answer
a) The heat absorbed when a liquid turns into a gas

In an endothermic reaction, the system:
a) Releases heat to the surroundings
b) Absorbs heat from the surroundings
c) Maintains constant temperature
d) Increases entropy

Answer
b) Absorbs heat from the surroundings

The enthalpy change for the reaction: H₂(g) + ½ O₂(g) → H₂O(l) is:
a) Negative and exothermic
b) Positive and endothermic
c) Zero and isothermal
d) Positive and exothermic

Answer
a) Negative and exothermic

For the reaction: A + B → C + D, if ΔH = +10 kJ/mol, the reaction is:
a) Exothermic
b) Endothermic
c) Isothermal
d) Adiabatic

Answer
b) Endothermic

The heat absorbed or released during a reaction can be measured using:
a) A calorimeter
b) A thermometer
c) A voltmeter
d) A spectrometer

Answer
a) A calorimeter

If a reaction is carried out in multiple steps, the overall enthalpy change can be determined by:
a) Adding the enthalpy changes of the individual steps
b) Subtracting the enthalpy changes of the individual steps
c) Averaging the enthalpy changes of the individual steps
d) Multiplying the enthalpy changes of the individual steps

Answer
a) Adding the enthalpy changes of the individual steps

The enthalpy change of reaction can be calculated from:
a) The bond energies of the reactants and products
b) The temperature change of the system
c) The pressure change in the system
d) The concentration of the reactants and products

Answer
a) The bond energies of the reactants and products

The enthalpy change for a reaction is independent of:
a) The path taken
b) The temperature
c) The pressure
d) The physical state of the reactants and products

Answer
a) The path taken

The enthalpy change of solution is:
a) The heat absorbed or released when a solute dissolves in a solvent
b) The heat absorbed or released during a phase change
c) The heat absorbed or released during a chemical reaction
d) The heat absorbed or released when a solid melts

Answer
a) The heat absorbed or released when a solute dissolves in a solvent

For the reaction: 2H₂(g) + O₂(g) → 2H₂O(g), if ΔH is -150 kJ/mol, the reaction is:
a) Endothermic
b) Exothermic
c) Isothermal
d) Isobaric

Answer
b) Exothermic

The enthalpy change of reaction can be expressed in:
a) kJ/mol
b) J/g
c) kJ/g
d) J/mol

Answer
a) kJ/mol

The enthalpy change of formation for an element in its standard state is:
a) Zero
b) Positive
c) Negative
d) Variable

Answer
a) Zero

The enthalpy change for the dissolution of a salt in water is known as:
a) Enthalpy of solution
b) Enthalpy of formation
c) Enthalpy of combustion
d) Enthalpy of vaporization

Answer
a) Enthalpy of solution

For an endothermic reaction, the enthalpy change is:
a) Positive
b) Negative
c) Zero
d) Equal to the change in entropy

Answer
a) Positive

The enthalpy change for a reaction that absorbs heat from the surroundings is:
a) ΔH > 0
b) ΔH < 0
c) ΔH = 0
d) ΔH is variable

Answer
a) ΔH > 0

The enthalpy change for a reaction at constant pressure is often measured in:
a) kJ/mol
b) J/g
c) kJ/g
d) J/mol

Answer
a) kJ/mol

The enthalpy change of a reaction can be affected by:
a) Temperature
b) Pressure
c) Concentration
d) All of the above

Answer
d) All of the above

If a reaction absorbs 50 kJ of heat, the ΔH for the reaction is:
a) +50 kJ
b) -50 kJ
c) 0 kJ
d) 50 kJ

Answer
a) +50 kJ

The enthalpy change for the reaction of hydrogen with oxygen to form water is:
a) Positive and endothermic
b) Negative and exothermic
c) Zero and isothermal
d) Variable depending on conditions

Answer
b) Negative and exothermic

The enthalpy change for a reaction can be determined using:
a) Hess’s Law
b) Dalton’s Law
c) Raoult’s Law
d) Henry’s Law

Answer
a) Hess’s Law

The heat absorbed or released during a reaction at constant volume is known as:
a) The change in internal energy
b) The enthalpy change
c) The change in entropy
d) The change in Gibbs free energy

Answer
a) The change in internal energy

The enthalpy change for the reaction: A + B → C + D, if ΔH = -20 kJ/mol, indicates:
a) The reaction is exothermic
b) The reaction is endothermic
c) The reaction is isothermal
d) The reaction is adiabatic

Answer
a) The reaction is exothermic

The enthalpy change associated with the dissolution of a substance is:
a) Enthalpy of solution
b) Enthalpy of formation
c) Enthalpy of combustion
d) Enthalpy of vaporization

Answer
a) Enthalpy of solution

The enthalpy change for the reaction of hydrochloric acid with sodium hydroxide to form water is:
a) Endothermic
b) Exothermic
c) Isothermal
d) Adiabatic

Answer
b) Exothermic

The enthalpy change for a reaction can be calculated from:
a) The heat absorbed or released during the reaction
b) The change in volume of the system
c) The change in pressure of the system
d) The change in concentration of the reactants and products

Answer
a) The heat absorbed or released during the reaction

The enthalpy change for a reaction can be affected by:
a) The pressure
b) The temperature
c) The concentration of reactants
d) All of the above

Answer
d) All of the above

The enthalpy change for a reaction is generally measured under:
a) Constant pressure
b) Constant temperature
c) Constant volume
d) Constant concentration

Answer
a) Constant pressure

The enthalpy change of a reaction can be determined using:
a) A calorimeter
b) A pH meter
c) A conductivity meter
d) A spectrophotometer

Answer
a) A calorimeter

The enthalpy change of a reaction can be calculated from:
a) The difference in the heat content of reactants and products
b) The temperature change of the system
c) The pressure change of the system
d) The concentration of the reactants

Answer
a) The difference in the heat content of reactants and products

The enthalpy of reaction is typically expressed in:
a) kJ/mol
b) J/g
c) kJ/g
d) J/mol

Answer
a) kJ/mol

The enthalpy change for a reaction is positive when:
a) The reaction is endothermic
b) The reaction is exothermic
c) The reaction is isothermal
d) The reaction is adiabatic

Answer
a) The reaction is endothermic

The enthalpy change for a chemical reaction is the heat absorbed or released:
a) At constant volume
b) At constant temperature
c) At constant pressure
d) At constant concentration

Answer
c) At constant pressure

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