Make sure you know the definitions below as they are easy marks to get in AS/A-level Chemistry exam! 👩‍🏫

Definitions 

• Hess's Law

         The enthalpy change is independent of the path taken. 

• Bond Enthalpy 

         The energy required to break 1 mole of gaseous bonds to form gaseous atoms. 

• Standard Enthalpy Change of Combustion 

         The enthalpy change when 1 mole of a substance undergoes complete combustion in its standard state. 

• Standard Enthalpy Change of Formation

         The enthalpy change when 1 mole of a compound is formed in its standard state from its elements in their standard  states. 

Enthalpy Calculations procedures:

1. See what value you have to find
2. Write the correct equation for the change 
3. See what data is provided 
4. Select the method of calculation which uses the data and apply Hess's Law
5. Check the sign and units for ΔH

Reference:

https://getrevising.co.uk/files/documents/enthalpy_summary/enth.pdf

This is the end of the topic!

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