Question

What volume of propane consumes one litre of oxygen during its complete combustion?

Answer 1

0.2 L of propane is required for every litre of oxygen consumed.

Explanation:

The balanced equation is

`color(white)(mmmmmm)"C"_3"H"_8 + "5O"_2 → "3CO"_2 + "4H"_2"O"`
`"Vol. ratio:"color(white)(mll)"1 L"color(white)(mm)"5 L"color(white)(mmll)"3 L"color(white)(mmll)"4 L"`

According to Gay-Lussac's Law of Combining volumes, the ratios of the volumes are the same as the ratios of the molecules (the coefficients in the balanced equation).

Hence

`"Vol. of C"_3"H"_8 = 1 color(red)(cancel(color(black)("L O"_2))) × ("1 L C"_3"H"_8)/(5 color(red)(cancel(color(black)("L O"_2)))) = "0.2 L C"_3"H"_8`

∴ 0.2 L of propane is required for every litre of oxygen consumed.