Question

What mass of C4H1O needs to be burned to produce 12 g of H2O?

Answer 1

number of mole of H2O = (mass of H2O)/(molar mass of H2O)
= 12/18
= 0.667 mole

reaction
2C4H10 + 5O2 --> 8CO2 + 10H2O
according to reaction
10 mol of H2O is formed from 2 mol of C4H10
1 mol of H2O is formed from 2/10 mol of C4H10
0.667 mol of H2O is formed from (2/10)*0.667 mol of C4H10
so,
number of mole of C4H10 required = 0.133 mole

molar mass of C4H10 = 58 g/mol
mass of C410 required = (number of mole of C4H10 required)*(molar mass of C4H10)
= 0.133*58
= 7.7 g

Answer : 7.7 g