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Molar Enthalpy Change

Chemistry: Edexcel IGCSE, topic 14.1.6

Molar Enthalpy Change

The change in heat during a reaction carried out at a constant pressure is known as an enthalpy change. We can work out the enthalpy change per mole of substance. This is called the molar enthalpy change and the symbol for this is ΔH.

Step 1

Step 1

  • Work out the enthalpy change using the equation:
  • Heat energy transferred = mass × specific heat capacity × temperature change
  • Q = mcΔT
Step 2

Step 2

  • Calculate the number of moles using the equation:
  • moles = mass ÷ relative formula mass (Mr)
  • mol = m ÷ Mr
Step 3

Step 3

  • Divide the heat energy transferred by the number of moles.
  • Molar enthalpy change = heat energy transferred ÷ moles.
  • ΔH = Q ÷ mol

Test yourself on Molar Enthalpy Change

  • What's the symbol for molar enthalpy change?

  • Working out Molar Enthalpy Change

  • Which of these is not an equation you need to use to work out molar enthalpy change?

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