Molecular Formula

Molecular Formula • Agenda • Review naming, mole town, formulas • Check EF • Notes on MF

Review naming • Carbon tetrabromide • Tin (II) chloride • Carbonic acid • Iron (III) acetate • Magnesium ion • Sulfide

Mole Town

% composition

Cu2O CH2O CH Fe2O3 CuO K2SO4 HgO MgCl2 BaCl2 FeS Empirical Formula

Molecular Formula Date:

Molecular Formula • A whole # multiple of the empirical formula • Can be a multiple of one too • EF and MF are the same in this case.

Easiest Method • Multiply MM of MF by percent composition & divide by respective atomic masses. Answer = subscript of MF.

Example A compound is 40% C, 6.7% H and 53.3 % O with a MM of 60. • C: 60 * 0.4 / 12 = 2 • H: 60 * 0.067 /1 = 4 C2H4O2 • O: 60 * 0.533 / 16 = 2 • If EF is desired, reduce ratio of subscripts. CH2O • This MF is a multiple of 2 of the EF

Longer Method – uses procedure learned with EF

A compound is 40% C, 6.7% H and 53.3 % O with a MM of 60. Step 1 C: 40/12 = 3.3 = 1 H: 6.7/1 = 6.7 divide by 3.3 = 2 O: 53.3/16 = 3.3 = 1 EF: CH2O

Step 2 • Find molar mass of EF. 30 • Step 3 • Divide molar mass of MF by EF to get multiple. 60/30 = 2 • Step 4 • Multiply subscripts of EF by multiple to get MF. C2H4O2

Molecular Formula