In the lab, there are a few different ways to find out the empirical and molecular formulas of substances. Here are some of the main techniques:

1. Mass Spectrometry: This method helps us find the molecular weight of a compound. Knowing the weight is important because it helps us calculate the molecular formulas.

2. Combustion Analysis: This technique is great for organic compounds. It involves burning a sample and measuring the amounts of carbon dioxide (CO₂) and water (H₂O) produced. By knowing these amounts, we can determine how much carbon and hydrogen is in the sample, which helps us figure out the empirical formula.

3. Percent Composition: We can also find the empirical formula by looking at the percent composition of elements in a sample. We use this formula:

   $\text{Percent by mass} = \left( \frac{\text{mass of element}}{\text{total mass of compound}} \right) \times 100$

   This tells us how much of each element is in the compound based on their mass.

4. Stoichiometric Calculations: By calculating the moles of reactants and products using balanced chemical equations, we can effectively find both empirical and molecular formulas.

In simple terms, the empirical formula shows the simplest whole-number ratio of elements in a substance. The molecular formula, on the other hand, tells us the actual number of atoms in a molecule.