Enthalpy

Question 1

What is enthalpy?

Answer 1

The thermal energy stored in a chemical system, cannot be measured absolutely

Question 2

What is the equation for enthalpy change?

Answer 2

Enthalpy change = products - reactants

Question 3

What is the activation energy?

Answer 3

The minimum energy required for a reaction to take place

Question 4

What is the standard temperature ?

Answer 4

298 K (kelvin) ,25celsius

Question 5

What is the standard pressure ?

Answer 5

100kPa (kilopascals)

Question 6

What is the standard concentration ?

Answer 6

1 mol dm-3

Question 7

What id the unit for standard enthalpy change?

Answer 7

kJ mol-1

Question 8

What is the standard enthalpy change of combustion ?

Answer 8

The enthalpy change when one molecule of a substance reacts completely with oxygen under standard conditions and all of the chemicals are in their standard states

Question 9

What is the standard enthalpy change of neutralisation ?

Answer 9

The enthalpy change when one molecule of water is formed in a neutralisation reaction under standard conditions

Question 10

What is the standard enthalpy change of formation ?

Answer 10

The enthalpy change when one molecule of a compound is formed from its elements under standard conditions and all of the chemicals are in their standard states

Question 11

What is the standard enthalpy change of reaction?

Answer 11

The enthalpy change when a reaction is the enthalpy change when a reaction takes place in the molar quantities shown by the balanced chemical equation under standard conditions and all of the chemicals must be in their standard states

Question 12

How do catalysts work?

Answer 12

Catalysts work to lower the activational energy by providing an alternate pathway

Question 13

What is meant by the term average bond enthalpy?

Answer 13

The breaking of 1 mol of bonds in gaseous molecules, averaged over different chemical environments