2.2 Thermochemistry

Question 1

energy change of a reaction in joules

Answer 1

E=mc∆T
Where m is the mass of water or solution and c is the specific heat capacity of water
4.18 Jg-1K-1

Energy = J

Question 2

eg enthalpy change calculation

Answer 2

Question 3

Hess’s law states

Answer 3

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

Question 4

Enthalpy changes have the symbol

Answer 4

ΔH and the units kJmol
−1
.

Question 5

enthalpy change of formation

Answer 5

Question 6

enthalpy change of combustion

Answer 6

Question 7

All enthalpy changes are measured in standard conditions:

Answer 7

25˚C or 298 K and 1 atmosphere (atm) or 101kPa pressure.

Question 8

Exothermic enthalpy changes

Answer 8

have a negative sign and endothermic enthalpy changes have a positive sign.

Question 9

Answer 9

0

Question 10

EG of enthalpy change of formation

Answer 10

Question 11

Answer 11

Question 12

bond enthalpy value

Answer 12

The amount of energy that is needed to break a bond

this is the same amount of energy that is given out when that bond is made

Breaking bonds requires energy. Energy is given out when bonds are made.

Question 13

Average bond enthalpy

Answer 13

is the energy required to break one mole of a bond in a gaseous species under standard conditions.

Question 14

enthalpy change is negative.

Answer 14

exothermic reaction