This is an example of a combustion reaction. To answer this you must first balance the equation.

The easiest way is to set up the reaction equation without any coefficients:

C2H6O + O2 --> CO2 + HOH

Now start balancing, first with carbon, then with hydrogen and last the oxygen.

There are 2 carbons on the left and 6 hydrogens so you add a coefficient of 2 in front of the CO2 and a 3 in front of the water.

C2H6O + O2 --> 2 CO2 + 3 HOH

Now count the number of oxygen on the product side and you get seven. One oxygen came from the ethanol so you need 6 more from oxygen. Add a coefficient of 3 in front of the oxygen on the reactant side and your reaction is balanced.

C2H60 + 3 O2 --> 2 CO2 + 3 HOH

This shows you that for every mole of ethanol, you will get 3 moles of water. So if you start with 0.51 moles of ethanol, you will produce 3 x .51 or 1.53 moles of water.