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Chapter 6: Problem 21

Define these terms: enthalpy, enthalpy of reaction. Under what condition is the heat of a reaction equal to the enthalpy change of the same reaction?

Short Answer

Expert verified
Enthalpy is a property of a system, calculated as the sum of its internal energy and the product of its pressure and volume. Enthalpy of reaction is the change in enthalpy during a chemical reaction, calculated as the difference of enthalpy of the products and reactants. The heat of a reaction equals enthalpy change when the reaction occurs under constant pressure and no non-pressure-volume work is done on or by the system.

Step by step solution

01

Define Enthalpy

Enthalpy (\(H\)) is a thermodynamic property of a system. It is the sum of the internal energy (\(U\)) of the system and the product of its pressure (\(P\)) and volume (\(V\)). This can be represented by the formula: \(H = U + PV\).
02

Define Enthalpy of Reaction

Enthalpy of reaction, or heat of reaction, is the change in enthalpy of a chemical reaction that occurs at a constant pressure. It is represented as \(螖H\) and calculated as the difference in enthalpy of the products and reactants: \(螖H = H_{products} - H_{reactants}\).
03

Conditions for Heat of Reaction Equal to Enthalpy Change

The heat of a reaction (\(q\)) is equal to the enthalpy change of the reaction (\(螖H\)) under conditions of constant pressure and no non-pressure-volume work being done on or by the system. When these conditions are met, we can write: \(q_p = 螖H\).

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