Define the law of multiple proportions explain with example


Staff member
Nov 4, 2019
The law of multiple proportions states that if two elements A and B combine together to form more than one compound, then two several masses of A. which separately combine with a fixed mass of B are in simple ratio.

In order to demonstrate the Law experimentally we make use of the fact that copper(l) oxide, Cu2O. Pure samples of these two can be reduced in a current of hydrogen and the masses of copper which combine separately with say 100g of oxygen in the two compounds, are calculated from the weightings.

Experiment 1

A test of the Law of Multiple Proportions

Weigh two clean dry porcelain boats and weigh them again containing samples of pure, dry copper(l)oxide Cu2O, and copper(ll) oxide respectively. Reduce the oxides to copper in a stream of dry hydrogen, as described in the last experiment. When the samples are cool weigh each of them in the porcelain boats.

Below is a table of specimen results and calculations.

Specimen Results

Copper(l) oxide Copper(ll)oxide

Mass of boat 6.90g 7.30g
Mass of boat and oxide 9.75g 9.20g
Mass of boat and copper 9.43g 8.82g
Therefore the Mass of copper 2.53g 1.52g
Mass of Oxygen 0.32g 0.38g

0.32g oxygen is combined with 2.53g copper. 100g oxygen are combined with
2.53 x 100
0.32 g copper