1. Chapter 2 – Analysis by Mass

2. Gravimetric Analysis
The quantitative analysis of substances based on the measurement of mass is called gravimetric analysis.
It is also used to determine the chemical formula of a compound.

3. Empirical Formulas
Chemical analysis enables us to determine the empirical formula of a compound.
This is the simplest whole number ratio of the atoms present in the compound.

4. Finding the Empirical Formula
Set up the ratio
Find the moles of each substance
Divide all results by the smallest number
Write empirical formula

5. Molecular Formulas
A molecular formula gives the actual number of atoms of each element present in a molecule of a compound.
The molecular formula of a compound is not necessarily the same as the empirical formula.

6. Finding the Molecular Formula
Find empirical formula.
Find M of empirical formula
Divide molar mass in question by this number.
Multiple empirical formula by this result.
Write molecular formula.

7. Calculating Masses of Reactants and Products
Write a balanced equation.
Calculate the amount, in mol, of the substance with the known mass.
Use mole ratio to find amount, in mol, of substance from question.
Answer the question…find the mass of this substance.

8. Excess Reactants Write a balanced equation.
Find the amount, in mol, of both reactants.
Determine which is in excess, using the mol ratios.
Use limiting reagent to find mol of substance in question.
Answer the question…find the mass.