Standard Enthalpy Changes

Question 1

What are standard conditions?

Answer 1

• Pressure of 100 kPa
• temperature of 298K

Question 2

Describe the standard enthalpy change of combustion.

Answer 2

The enthalpy change when one mole of a substance reacts completely with oxygen under standard conditions in their standard states.

Question 3

Describe the standard enthalpy change of formation.

Answer 3

The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states, under standard conditions.

Question 4

What is the standard enthalpy change of formation for all elements?

Answer 4

0 KJ/mol

Question 5

Describe the standard enthalpy change of neutralisation.

Answer 5

The enthalpy change that takes place when an acid reacts with a base to form one mole of water under standard conditions, in their standard states.

Question 6

Why are the standard values from the data book different to calculated values?

Answer 6

• Incomplete combustion
• heat loss to surroundings
• evaporation
• non-standard conditions