general chemistry

Question

What mass of water is produced from the complete combustion of 7.50×10⁻³ gg of methane?

Answer 1

Methane = CH₄

Molar mass CH₄ = 16.0 g / mole

CH₄ + 2O₂ ==> CO₂ + 2H₂O .. balanced equation for combustion of methane

moles CH₄ used = 7.50x10^-3 g x 1 mol / 16.0 g = 4.6875x10^-4 moles

moles H₂O produced = 4.6875x10^-4 moles CH₄ x 2 mol H₂O / mol CH₄ = 9.375x10^-4 mols H₂O

mass H₂O = 9.375x10^-4 mols H₂O x 18.0 g H₂O / mol = 0.0169 g H₂O (3 sig. figs.)