[Foobarz]

Ok, the question is that

10.0 g of hydocarbons increasing in molar mass (C2H6, C3H8, C4H10) are burned. Which hydrocarbon will produce the greatest mass of H2O?

My guess is that it will be the C2H6, since it has the lowest molar mass and therefore the most number of moles in 10.0 g, and thus producing the most number of moles of CO2.

[Borek]

Even if you are right, your explanation doesn't make much sense. Number of moles of hydrocarbon doesn't matter, what matters is a number of moles of hydrogen in 10 g of the substance.

It is a simple stoichiometry, so it is easy to check which answer is the right one.