# How do you calculate the empirical formula of a compound formed from 3% C, 0.3% H, and 96.7% I?

Apr 27, 2016

Assume that 100 grams contains:
3 grams of C, 0.3 grams of H, and 96.7 grams of I.

Next step, calculate the number of moles of each atom using the formula $n = m \div M$.
n = number of moles
m = mass of substance
M = molar mass

The number of moles (n) for:
Carbon = 3 grams $\div$ 12.0 g/mol = 0.25 moles
Hydrogen = 0.3 grams $\div$ 1.0 g/mol = 0.30 moles
Iodine = 96.7 grams $\div$ 127 g/mol = 0.76 moles

Then, divide all number of moles BY THE SMALLEST above and round to nearest whole number.
Carbon = 0.25 $\div$ 0.25 = 1.00
Hydrogen = 0.30 $\div$ 0.25 = 1.00
Iodine = 0.76 $\div$ 0.25 = 3.00

Assign them as subscripts.
Therefore, the empirical formula is $C H {I}_{3}$