the empirical formula of an organic compound is c2 h4 o2 if the relative formula mass of the compound is 120 determine the molecular formula of the compound and hence the percentage composition of each element in the compound (c=12,H=1,0=16)
To determine the molecular formula, we need to find the actual formula mass of the compound. We can do this by dividing the relative formula mass by the empirical formula mass:
actual formula mass = 120 / (2(12) + 4(1) + 2(16))
actual formula mass = 120 / 44
actual formula mass = 2.73
To find the molecular formula, we need to multiply the empirical formula by a whole number that gives us the actual formula mass. We can do this by dividing the actual formula mass by the empirical formula mass:
molecular formula multiplier = actual formula mass / empirical formula mass
molecular formula multiplier = 2.73 / 0.108
molecular formula multiplier = 25.3
We can then multiply each subscript in the empirical formula by 25.3 to get the molecular formula:
C2H4O2 x 25.3 = C50.6H101O50.6
To find the percentage composition by element, we need to find the mass of each element in one mole of the compound and divide by the molar mass of the compound:
mass of C in one mole of compound = 2(12.01) / 120
mass of C in one mole of compound = 0.201 g/mol
% composition of C = (0.201 / 2.73) x 100%
% composition of C = 7.37%
mass of H in one mole of compound = 4(1.01) / 120
mass of H in one mole of compound = 0.0334 g/mol
% composition of H = (0.0334 / 2.73) x 100%
% composition of H = 1.22%
mass of O in one mole of compound = 2(16.00) / 120
mass of O in one mole of compound = 0.533 g/mol
% composition of O = (0.533 / 2.73) x 100%
% composition of O = 19.5%
Therefore, the compound has a molecular formula of C50.6H101O50.6 with 7.37% C, 1.22% H, and 19.5% O.