Calculate the energy requirements in the following scenarios.


Q1. Calculate the energy needed to break all of the bonds in 1 mole of Methane.


A1. Methane is:

The bond energy (enthalpy) of the C-H bond in this case is 413 kJ mol-1 and each molecule has 4 such bonds. The total MOLAR energy required would therefore be:



Q2. Calculate the energy needed to break all of the bonds in 2 moles of Ethane.


A2. Ethane is:

Therefore we have 1 x C-C single bond and 6 x C-H single bonds.


C-C = 347 kJmol-1

C-H = 413 kJmol-1


The MOLAR energy would therefore be: 


Q3. Calculate the energy needed to break all of the bonds in 1 mole of Ethyl Ethanoate.


A3 Ethyl Ethanoate (Ethyl Acetate) is an ester produced by reacting Ethanoic Acid with Ethanol, and has this displayed formula:

When the molecules start to become a little unwieldy it is best to make a small table of the bonds present, and their numbers and energies:


C-H

8

413 kJmol-1

C-C

2

347 kJmol-1

C-O

2

358 kJmol-1

C=O

1

745 kJmol-1


The calculation can now be completed by multiplying the respective bond energies by the number of instances of each, and then add them up.






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