Multiple Choice
Given the reaction 2C6H6(l) + 15O2(g) → 12CO2(g) + 6H2O(l), what is the standard enthalpy change (ΔH°) of this reaction in kJ?
8. Thermochemistry
Enthalpy of Formation
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Which of the following statements is true regarding the enthalpy change of a reaction when the quantities of reactants are doubled?
A
The enthalpy change is halved.
B
The enthalpy change remains the same.
C
The enthalpy change is doubled.
D
The enthalpy change becomes zero.
Verified step by step guidance1
Understand the concept of enthalpy change: Enthalpy change (ΔH) is a measure of the heat absorbed or released during a chemical reaction at constant pressure. It is an extensive property, meaning it depends on the amount of substance involved in the reaction.
Recognize that enthalpy change is proportional to the quantity of reactants: Since enthalpy is an extensive property, if the quantity of reactants is doubled, the enthalpy change will also double, assuming the reaction conditions remain the same.
Consider the stoichiometry of the reaction: When the quantities of reactants are doubled, the stoichiometry of the reaction indicates that twice the amount of product will be formed, which requires twice the amount of energy change.
Apply the principle of proportionality: If the reaction is written as A + B → C with an enthalpy change ΔH, then doubling the reactants to 2A + 2B → 2C will result in an enthalpy change of 2ΔH.
Conclude with the correct statement: Based on the understanding that enthalpy change is proportional to the amount of reactants, the correct statement is that the enthalpy change is doubled when the quantities of reactants are doubled.
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