How many moles of water are produced from 40.0 g of C2H6?

4 moles of water

Explanation:

this is a combustion reaction, so the balanced equation is: 2C2H6 + 7O2 → 4CO2 + 6H2O.

the molar mass of C2H6 is 30.07g, so 40.0 g of C2H6 is 1.33 moles of C2H6.

mole ratio of H2O to C2H6 is 6/2, or 3.

1.33 moles C2H6 * 3 moles H2O/1 mole C2H6 = 4 moles H2O