Name: _______________________
Bond Energies Prep
For the following questions you will need the following bond energies.
Bond
Br-Br
H-H
H-Br
NN
N-H
C-C
E (X-Y)/
kJ mol-1
193
436
366
945
391
346
Bond
C-H
O=O
O-H
C-O
C=O
1. What exactly does a bond energy represent?
E (X-Y)/
kJ mol-1
413
498
464
336
805
2
2. Why do even exothermic reactions need energy to get them started, and what
is that energy called?
2
3. What do we mean by the heat of reaction, and how is it related to the bond
energy of the reactants and the bond energy of the products.
2
4. Calculate the heat of reaction for the following reaction. You must include a
sign and units in your answer. State whether the reaction is exothermic or
endothermic and explain how you arrived at this conclusion.
4
2 HBr (g)  H2 (g) + Br2 (g)
5. Calculate the energy change that takes place during the Haber Process. Use
your notes to help you. Include a sign and units.
3
N2 (g) + 3 H2 (g)  2 NH3 (g)
6. Use your notes carefully in this question to help you.
For each of the following reactions draw out the reactant and product
molecules and calculate the energy change.
You should notice that the difference between them increases by the same
amount each time. Why is this?
To answer this look carefully at the patterns in the equations for the reactions
and the similarity of the alcohol molecules reacting.
7
Answer this question on file paper and hand it in with the rest of the work.
Ethanol:
C2H5OH + 3 O2  2 CO2 + 3 H2O
Propanol:
C3H7OH + 4 ½ O2  3 CO2 + 4 H2O
Butanol:
C4H9OH + 6 O2  4 CO2 + 5 H2O