Law of multiple proportions states that if two elements form more than one compound, then the ratios of the masses of the second element which combine with a fixed mass of the first element will always be ratios of small whole numbers. This law is sometimes called Dalton’s Law, named after John Dalton, the chemist who first expressed it.
2.66 g chloride of a metal when treated with silver nitrate solution give 2.87 g of silver chloride. 3.37 g of another chloride of the same metal give 5.74 g of silver chloride when treated with silver nitrate solution. Show that the results are in agreement with a law of chemical combination.
Solution:
Molar mass of silver chloride = (108+35.5) = 143.5g
Mass of silver in 143.5 g of silver chloride = 108 g
Case 1: Mass of silver in 2.87 g of silver chloride = (108/143.5) * 2.87 = 2.16 g
Mass of chlorine = 2.87- 2.16 = 0.71 g
Mass of metal in metal chloride =(2.66−0.71) = 1.95 g
Case 2: Mass of silver in 5.74 g of silver chloride = (108/143.5) * 5.74 = 4.32 g
Mass of chlorine = 5.74 – 4.32 = 1.42 g
Mass of metal in metal chloride = (3.37−1.42) = 1.95 g
So, the mass of chlorine combining with the constant mass of metal (i.e., 1.95 g) are in the ratio of 0.71 : 1.42 or 1 : 2.
It is a simple whole number ratio.
Hence this results in agreement with the law of multiple proportions.
Read More: Complete Beginner’s Guide to Mole Concept