Determine the empirical formula of an unknown Compound having a percent composition of 3.74% H, 17.83% C, and 38.43 % Pb.(Molar mass: Pb =207.20 g/mol; C=12.01 g/mol; H = 1.01 g/mol).

Answer 1

To determine the empirical formula, we need to find the smallest whole number ratio of atoms in the compound.

1. Calculate the number of moles of each element:

H: 3.74 g / 1.01 g/mol = 3.71 mol
C: 17.83 g / 12.01 g/mol = 1.48 mol
Pb: 38.43 g / 207.2 g/mol = 0.185 mol

2. Find the smallest mole ratio by dividing each value by the smallest number of moles:

H: 3.71 mol / 0.185 mol = 20.05 ≈ 20
C: 1.48 mol / 0.185 mol = 8
Pb: 0.185 mol / 0.185 mol = 1

3. Write the empirical formula using the whole number ratios:

Empirical formula = PbC8H20