Calculate the mass of water produced when 6.68 of butane reacts with excess oxygen

1.What is the molar mass of butane? this is 58.12 g/mol
2.Calculate the mass of water produced when 6.68 of butane reacts with excess oxygen
3.Calculate the mass of butane needed to produce 51.8 of carbon dioxide.

2 C4H10 + 13 O2 → 10 H2O + 8 CO2

Supposing the missing units in both cases to be "grams":
2.
(6.68 g butane) / (58.12 g butane/mol) x (10/2) x (18.01532 g H2O/mol) = 10.4 g H2O

3.
(51.8 g CO2) / (44.00964 g CO2/mol) x (2/8) x (58.12 g butane/mol) = 17.1 g butane