Answer:
7.52x10^24 molecules of H2O.
Step-by-step explanation:
1) We need to start with a balanced equation for this reaction, combustion of methane:
CH4 + 2O2 →CO2 + 2H2O
This tells us that 1 mole of methane will produce 2 moles of water. (2 moles H2O)/(1 mole CH4)
2) Find the moles of methane in 100g of the molecule. The molar mass of methane is 16.0 g/mole.
Moles CH4 = (100g/16.0 g/mole) = 6.25 moles CH4
3) Multiply 6.25 moles CH4 by the molar ratio from (1):
(6.25 moles CH4)( (2 moles H2O)/(1 mole CH4) = 12.50 moles H2O [the moles CH4 cancel]
4) Multiply the moles H2O by Avogadro's number: 6.02x10^23 molecules/mole
(12.50 moles H2O)*(6.02x10^23 molecules/mole) = 7.52x10^24 molecules of H2O.