EASY
AS and A Level
IMPORTANT
Earn 100

Use the information in Figure and the information below to demonstrate that the average bond energy of the C-H bond is 415.9 kJ mol-1.

Question Image

Hf°CH4=-74.8 kJ mol-1.Hat°12H=+218 kJ mol-1.Hat°Cgraphite=+716.7 kJ mol-1.

Important Questions on Enthalpy Changes

EASY
AS and A Level
IMPORTANT

Look at this equation.

CH4(g)+2O2gCO2g+2H2Og.

Which one of the following statements is completely correct?

MEDIUM
AS and A Level
IMPORTANT

When red phosphorus burns in oxygen the enthalpy change is -2967 kJ mol-1. For white phosphorus the enthalpy change is -2984 kJ mol-1. For both forms of phosphorus the reaction taking place is: P4s+5O2gP4O10s.

Use this information to calculate the enthalpy change for the transformation: P4whiteP4red.

EASY
AS and A Level
IMPORTANT
Calculate the standard enthalpy change of formation of methane from the following standard enthalpy changes of combustion:
carbon=-394 kJ mol-1.hydrogen=-286 kJ mol-1.methane=-891 kJ mol-1.
EASY
AS and A Level
IMPORTANT

Calculate the standard enthalpy change of combustion of methane using the following bond energies:

EC-H=+412 kJ mol-1.EO=O=+496 kJ mol-1.EC=O=+805 kJ mol-1.EO-H=+463 kJ mol-1.