You should be able to:
2.1a understand the concept of enthalpy change,
DH,
and the necessity to express this under
standard conditions
2.1b recall that DH
is negative for exothermic reactions, and positive for endothermic reactions
2.1c recall the definitions of standard enthalpy
of formation, DHqf,
standard enthalpy of combustion DHqc
and
standard enthalpy of neutralisation, DHqneut
.
· definitions should
make reference to ‘heat’ or ‘enthalpy’ change, not just ‘energy’
changes which is represented by U D , and is
not
required)
2.1d construct simple enthalpy level diagrams
2.1e understand that the sign of the enthalpy
change does not always indicate the direction of spontaneous change
· no treatment of the
thermodynamic terms ‘free energy’ and ‘entropy’ will be expected)
2.1f recall and apply Hess’s Law to calculate
enthalpy changes
2.1g describe experiments to measure values of
DH for
simple laboratory reactions and perform calculations based on the results
of these experiments (paper 3B only)
· limited to DHqc,
DHqneut,
and DHqfreactions,
such as displacement and precipitation, that could easily be carried out
in a school laboratory. Practical experiments using a bomb calorimeter
are not expected.)
2.1h use average bond enthalpy data to calculate
approximate enthalpy changes.