THINK ABOUT IT… A scientist has an 8g sample of radium. How many grams of the sample will decay in 800 years if the half-life is 1600 years? Read it carefully...a full half-life hasn’t passed yet! Don’t forget to label your units - g!

To answer this item, our basis is 100g. We solve for the masses of the given elements in this item,
 
            carbon:     (0.18)(100 g) = 18 g
            hydrogen:  (0.0226)(100 g) = 2.26 g
            chlorine:    (0.797)(100 g) = 17.7 g

Then, we calculate for the number of moles by dividing the masses by the molar masses of the given elements.

Number of moles:

              carbon = (18 g) x (1 mol / 12 g) = 1.5 moles
             hydrogen = (2.26 g) x (1 mol/ 1.01 g) = 2.23 moles
             chlorine = (79.7 g) x (1 mol / 35.45 g) = 2.25 moles

We get the ratio of the number of moles by dividing them with the lowest value, 1.5.
                      Carbon = 1.5 moles / 1.5 = 1
                      Hydrogen = 2.23 moles / 1.5 = 1.48
                      Chlorine = 2.25 / 1.5 = 1.5

The empirical formula is,
                     C1H1.5CL1.5
Simplifying,
                    C2H3Cl3