The combustion of how many moles of ethane would be required to heat 838 grams of water from 25.0 to 93.0 degrees C? Assume liquid water is formed during the combustion.

Answer 1

q is the amount of heat you will need to heat the 838 g water.
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)

Do you have the heat of combustion? If not you will need to calculate it.
2C2H6(g) + 7O2(g) ==> 4CO2(g) + 6H2O(l)
dHrxn = (n*dHf products) - (n*dHf reactants)
dHrxn is the heat of combustion.

dHrxn/2 x mol = q
Solve for mol. Remember to keep the units for dHrxn and q the same.