Enthalpy Change And Bond Energies

Question 1

What is enthalpy change

Answer 1

The overall change in energy during a reaction

Question 2

How would you measure enthalpy change using calorimetry through displacement, and neutralisation reactions

Answer 2

Put 25cm^3 of HCL and sodium hydroxide in separate beakers
Place the beakers in a water bath set to 25 degrees Celsius
Add the HCL follow by the NaOH or a polystyrene cup ( add cotton wool to provide a layer of insulation and reduce energy loss to surroundings)
Take the temperature of the mixture every 30 seconds and record the highest temperature

Question 3

How would you measure enthalpy change using calorimetry through combustion reactions

Answer 3

Use a screen to act as a draught excluder
Put 50g of water in a copper can and record its temperature
Weigh the spirit burner
Put the burner underneath the can and light the wick
Heat the can and stir until the temperature reaches 50 degrees Celsius
Put out the flame and measure the final temperature of the water
Weigh the spirit burner and lid again

Question 4

How can you calculate the Heat Energy Transferred

Answer 4

Heat energy transferred = mass x specific heat capacity x change in temperature of the liquid

Question 5

Describe the process of bond breaking

Answer 5

Endothermic reaction where energy is supplied to the broken bonds

Question 6

Describe the process of bond forming

Answer 6

Exothermic process where energy is released following the formation of bonds

Question 7

How can you calculate enthalpy change

Answer 7

Enthalpy change = total energy absorbed to break bonds - total energy released in making bonds