Empirical, Molecular and Percent Comp.

give the kind and number of atoms of each element present in a molecular compound.

Calculate the empirical formula mass (EFM), which is simply the molar mass represented by the empirical formula. Divide the molar mass of the compound by the empirical formula mass. The result should be a whole number or very close to a whole number. Multiply all the subscripts in the empirical formula by the whole number found in step 2. The result is the molecular formula.

Step 1:List the known quantities and plan the problem.

Step 2:Plug in

Step 3:Calculate.

shows the lowest whole-number ratio of the elements in a compound.

1.List the known quantities and plan the problem.

2.Assume its a 100 g sample!

3.Plug in and calculate!

percent by mass of each element in a compound

Step 1:List the known quantities and plan the problem.

Step 2:Calculate.

Step 3:Does this make sense?