9.4- Hess Law And Enthalpy Cycles

Question 1

What is the standard pressure ?

Answer 1

100KPa also known as 1atm

Question 2

What is the standard temperature ?

Answer 2

298K

Question 3

What is standard concentration ?

Answer 3

1 mol dm^-3

Question 4

What is standard state ?

Answer 4

Physical state of a substance under standard conditions

Question 5

Define standard enthalpy change of formation

Answer 5

The enthalpy change when one mole of a substance is formed from its elements in their standard states under standard conditions of 298K and 100KPa

Question 6

Define standard enthalpy change of combustion

Answer 6

The enthalpy change when one mole of a substance is completely burned In excess oxygen under standard conditions of 298K and 100KPa

Question 7

Define the standard enthalpy change of neutralisation

Answer 7

The enthalpy change when one mole of H2O is formed from the reaction of an acid with a base under standard conditions of 298K and 100KPa

Question 8

Define Hess’s Law

Answer 8

If a reaction can take place by two routes and the starting and finishing conditions are the same the total enthalpy is the same for each route