Question

if 6.0g of carbon is heated in air, the mass of the product obtained could either be 22.0g or 14.0g depending on the amount of air present , with what law will this be accordance ? (c=12 , o =16

Answer 1

Law of Multiple Proportions.
mols C = grams/atomic mass = 6/12 = 0.5
2C + O2 ==> 2CO
mols CO formed = 0.5 x (2 mols CO/2 mols C) = 0.5
grams C = 0.5 mols x molar mass CO = 0.5 x 28 = 14 g CO
OR
C + O2 ==> CO2
mols CO2 produced = 0.5 mols C x (1 mol CO2/1 mol C) = 0.5
grams CO2 = mols CO2 x molar mass CO2 = 0.5 x 44 = 22 g CO2
The Law of Multiple Proportions says that when two elements form more than one compound that the mass of one element that combines with a fixed amount of a seconc element the ratio is of small whole numbers. In this case, the amount of O that combines with a fixed amount of C (0.5 mol) the O will be in small whole numbers; i.e., 1 atom O to 2 atoms O. This law was proposed in 1804 by John Dalton.