Enthalpy

Question 1

Write an equation for the complete combustion of C5H4O2 in excess Oxygen?

Answer 1

C5H4O2 + 5O2 —> 5CO2 + 2H2O

Question 2

Name 5 pieces of data needed to practically calculate the enthalpy change of combustion of a fuel

Answer 2

Mass of fuel burnt
Change in temperature 
Mr of fuel
Specific heat capacity of water
Mass/volume of water

Question 3

Why would the value obtained practically for the enthalpy change of combustion be different from the value obtained using average bond enthalpies?

Answer 3

Incomplete combustion
Evaporation of fuel (from wick)
Non-standard conditions in experiment

Question 4

Suggest a reason why the use of non-food parts of crop plants is desirable for the production of biofuels.

Answer 4

Allows food crops to be used for food

Production of food not affected

Question 5

A value for ΔHc propane can be determined experimentally by burning a known mass of propane gas and allowing the energy to be transferred to water. Suggest two different practical limitations or difficulties with this experiment.

Answer 5

Incomplete combustion and heat loss to the surroundings.