Hi Brittney V.,
C3H8 + O2 ---> CO2 + H2O, from her I see I need 4H2 to make H8, and 3C to make C3,
C3H8 + 5O2 ---> 3CO2 + 4H2O, and 5O2 balances it.
C3H8 is 3*(12.0107g) + 8*(1.00794g) = 44.0956 g/mol
H2O is 2*(1.00794g) + 1*(15.9994g) = 18.0153g/mol
So how many g's H2O = 30.0g C3H8 ,
30.0 g C3H8 *(1 mol C3H8)*(4 mol H2O)*(18.0153 g H2O) = 49.026 g H2O or 49.0 g H2O (sig. fig.)
(44.0956 g C3H8) *(1 mol C3H8)*(1 mol H2O)
Check my work. It's been a while since I've done chemistry.
I hope this helps, Joe.