Enthalpy and Calorimetry

Flashcards covering key concepts related to enthalpy change, calorimetry, and thermodynamic principles from the lecture.

Enthalpy Change (∆Ho)

The heat energy change in a reaction represented by the symbol ∆Ho, measured under standard conditions.

Endothermic Reaction

A reaction in which more energy is needed to break bonds than to form them, resulting in a positive overall ∆H.

Exothermic Reaction

A reaction in which more energy is released during the formation of bonds than is needed to break existing bonds, resulting in a negative overall ∆H.

Enthalpy Change of Reaction (∆rHo)

The enthalpy change when quantities of substances in standard states react completely under standard conditions.

Enthalpy Change of Formation (∆fHo)

The enthalpy change when one mole of a substance is produced from its elements under standard conditions.

Enthalpy Change of Combustion (∆cHo)

The enthalpy change when one mole of a substance is burned completely in oxygen under standard conditions.

Enthalpy Change of Neutralisation (∆neutHo)

The enthalpy change when solutions of acid and alkali react together to produce one mole of water under standard conditions.

Calorimetry

An experimental method for finding enthalpy change by measuring temperature change over time during a reaction.

Specific Heat Capacity

The energy required to raise the temperature of 1 gram of a substance by 1 K without a change of state.

Hess's Law

Energy in a reaction system must be conserved; the overall enthalpy change for a reaction is the same regardless of the pathway taken.

Mean Bond Enthalpy

Averages value representing the energy required to break one mole of a specified bond in a gaseous state, under standard conditions.

Bond Enthalpy Calculation

The enthalpy change for a reaction is equal to the sum of the bond enthalpies for bonds broken minus the sum for bonds formed.

Calorimetry Errors

Inaccuracies in ∆H values found using calorimetry arise from heat loss to surroundings and measurement inaccuracies.

Energy Transfer in Reactions

Energy is absorbed from the surroundings to break bonds (endo) and released when new bonds form (exo).