Explanation:
We have to find the bonds that are broken and formed during the following reaction.
__ C₂H₄ + __ O₂ ---> __ CO₂ + __ H₂O
First we have to balance the reaction. To balance a combustion reaction we usually start balancing the atoms of C. We have two on the left and 1 on the right side of the equation. So the coefficient for CO₂ must be 2.
__ C₂H₄ + __ O₂ ---> 2 CO₂ + __ H₂O
Then we balance the H atoms by changing the coefficient for water. We have 4 atoms of H on the left and two on the right. The coefficient must be 2.
__ C₂H₄ + __ O₂ ---> 2 CO₂ + 2 H₂O
And finally we can balance the O atoms by changing the coefficient for O₂. We have 6 O atoms on the right side, so the coefficient for O₂ must be 3. The balanced equation is:
C₂H₄ + 3 O₂ ---> 2 CO₂ + 2 H₂O
Now to determine the bonds that have to be broken we have to pay attention to the Lewis structures of the reactants. They are:
We have to break 4 C-H bond, 1 C=C and 3 O=O bond (since the coefficient for oxygen gas is 3).
The bonds that we have to form are:
We have to form 4 C=O bonds (since the coefficient for carbon dioxide is 2), and 4 O-H bonds (since the coefficient for water gas is 2).
Answer: Four C-H, one C=C and three O=O bond need to break up. Four C=O and 4 O-H bonds need to form. (second option)
