Chemical Reactions

I. For the chemical reaction : C4H10 + O2 ------> CO2 + H2O
a) Balance the equation.
b) Why do we have to balance chemical equations?
c) What is the type of reaction?
d) If you start with 3 moles of Butane with enough oxygen, how many moles of water will be formed?

II. John has burned 756 g of log completely in his fire place to heat up his house. At the end of this process, John  was left with 106g of ashes.Describe in detail whether matter was destroyed or not during this process?