2.2 Law of Multiple Proportions

The Law of Multiple Proportions (Dalton’s Law) states that When two elements react, the mass of one element will react with masses of a second element so compounds always equals a ratio of small, whole number.

Compound A

32 grams of O reacts with 24 grams of C

\[\mathrm{ratio} = \dfrac{\mathrm{O}}{\mathrm{C}} = \dfrac{32}{24} = 1.33\]

Compound B

64 grams O reacts with 24 grams of C

\[\mathrm{ratio} = \dfrac{\mathrm{O}}{\mathrm{C}} = \dfrac{64}{24} = 2.66\]

\[\dfrac{\mathrm{Compound~A}}{\mathrm{Compound~B}} = \dfrac{2.66}{1.33} = \dfrac{2}{1}\]

Compound B has 2 O for every C; compound A has 1 O for every C.