Chemical Energetics

Define the term bond enthalpy

The enthalpy change when one mole of bonds are broken in the gas phase

What is enthalpy change?

A measure of the heat given out or taken in during a reaction

What is an endothermic reaction?

A reaction where heat energy is absorbed

Positive enthalpy change

What is an exothermic reaction?

A reaction where heat energy is released

Negative enthalpy change

What is activation energy?

The minimum energy required in order for a reaction to start

What are the standard conditions during a reaction?

* Pressure: 101kPa
* Temperature: 298K
* Concentration: 1 moldm3
* Substance in their most stable state

Define the standard enthalpy of combustion

The enthalpy change when one mole of a substance in its standard state burns completely in oxygen under standard conditions

Define standard enthalpy of formation

The enthalpy change when one mole of a substance in its standard state is formed from the pure elements in their standard states under standard conditions

Define Standard Enthalpy of Reaction

The enthalpy change when a reaction takes place in the molar quantities given in a chemical reaction under standard conditions

Define Standard Enthalpy of Neutralisation

The enthalpy change when one mole of water is formed by reacting an acid under standard conditions

Define Standard Enthalpy of Hydration

The enthalpy change that takes place when one mole of gaseous ions dissolves in water

Define Standard Enthalpy of Solution

The enthalpy change that occurs when one mole of an ionic solid dissolves in water

Define the Standard Enthalpy of Atomisation

The enthalpy change when one mole of gaseous atoms are formed from the element in its standard state

What is bond energy?

Energy required to break a mole of covalent bonds

Equation for enthalpy calculations

∆H = m x c x ∆T

What is Hess’ Law?

The enthalpy change of a reaction is independent to the pathway