Energetics

All the questions in energetics that I either didn't know are forgot

What are the standard conditions for measuring enthalpy change?

100Kpa and 298K

What is enthalpy change?

The change in heat energy during a reaction at constant pressure.

What is meant by an exothermic reaction?

An exothermic reaction is where energy is being transferred from a chemical reaction to the surroundings (heat energy).

Define the standard enthalpy change for formation?

Is the heat change for the formation of 1 mole of a substance from its elements all substances being in their most stable state under standard conditions 100Kpa and 298K.

Define the standard enthalpy change of combustion?

Is the heat change when 1 mole of the substance completely burns in excess oxygen, all substances being in their most stable states under standard conditions 100Kpa and 298K.

Define the standard enthalpy change of neutralisation?

Is the heat change when acid is neutralised by an alkali to produce 1 mole of water all in standard conditions 100Kpa and 298K.

State four reasons why the experimental value for the enthalpy of combustion of a fuel may be different to the value in a data book?

1. Incomplete combustion could have occurred.

2. The reaction was not taken place in standard conditions.

3. Heat was lost to the surrounding.

4. Evaporation occurred.

State Hess’s law:

The enthalpy change of a reaction is independent of the route taken.

bond enthalpy

the enthalpy change when one mole of a bond in the gaseous state is broken

mean bond enthalpy

the enthalpy change when one mole of a bond averaged out over many different molecules is broken

lattice energy

is the energy change when one mole of an ionic solid is formed from its gaseous ions under standard conditions

enthalpy change of atomisation

enthalpy change when one mole of gaseous atoms is produced form an element in its standard state

1st electron affinity

enthalpy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions

enthalpy change of solution

enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so the dissolved ions are well separated and don’t interact

enthalpy change of hydration

enthalpy change when one mole of gaseous ions become hydrated ( they dissolve in water)