A-Level Chemistry Edexcel 9CH0

know that standard conditions are 100 kPa and a specified temperature, usually 298 K

be able to calculate an enthalpy change of reaction using mean bond enthalpies and explain the limitations of this method of calculation

be able to calculate mean bond enthalpies from enthalpy changes of reaction

know that the enthalpy change is the heat energy change measured at constant pressure

be able to construct and interpret enthalpy level diagrams showing an enthalpy change, including appropriate signs for exothermic and endothermic reactions

Activation energy is not shown in enthalpy level diagrams but it is shown in reaction profile diagrams.

be able to define standard enthalpy change of:

i) reaction ii) formation iii) combustion iv) neutralisation

understand experiments to measure enthalpy changes in terms of:

i) processing results using the expression:

energy transferred = mass × specific heat capacity × temperature change (Q=mcΔT)

ii) evaluating sources of error and assumptions made in the experiments

*Students will need to consider experiments where:

• substances are mixed in an insulated container and the temperature change is measured
• enthalpy of combustion is measured, such as using a series of alcohols in a spirit burner
• the enthalpy change cannot be measured directly. *

be able to calculate enthalpy changes in kJ mol^-1 from given experimental results

Both a sign and units are expected in the final answer.

be able to construct enthalpy cycles using Hess’s Law

be able to calculate enthalpy changes from data using Hess’s Law

know what is meant by the terms ‘bond enthalpy’ and ‘mean bond enthalpy’

CORE PRACTICAL 8: To determine the enthalpy change of a reaction using Hess’s Law