Enthalpy

Question 1

What is enthalpy change?

Answer 1

H(product) - H(reactants)

Question 2

Describe an exothermic reaction

Answer 2

.Chemical system releases heat energy to the surroundings.
.Energy loss of system is balanced by energy gain of surroundings.
.Enthalpy change is negative.
Surrounding temperature increases.
.Products have less energy than reactants.

Question 3

Describe an endothermic reaction

Answer 3

.Chemical system takes heat energy from the surroundings.
.Temperature of the surroundings decreases.
.Enthalpy change is positive.
.Products have more energy than reactants.

Question 4

What is an activation energy?

Answer 4

Minimum energy required for a reaction to take place.

Question 5

What is the standard pressure?

Answer 5

100kPa

Question 6

What is the standard temperature?

Answer 6

usually 298K

Question 7

What is enthalpy change of formation?

Answer 7

formation of one mole of a compound from its elements.

Question 8

What is enthalpy change of combustion?

Answer 8

Complete combustion of one mole of a substance.

Question 9

What is enthalpy change of neutralisation?

Answer 9

formation of one mole of water from neutralisation.