Determine the empirical formula for the compound represented by each molecular formula. a. C2H4 b. C6H12O6 c. NH3

Understanding the chemical composition of a substance involves knowing what elements make it up and in what proportions. Imagine you're given different lego sets to build various objects. Each set contains legos of different colors (elements) and counts (proportions). Similarly, the chemical composition provides a 'list' of elements in a compound and how many atoms of each are present.

When chemists talk about the composition of a compound, they may refer to its empirical formula, which gives the simplest whole-number ratio of atoms of each element in the compound. This is like saying instead of having a pile of 100 red and 200 green legos, you show the ratio of 1:2, making it easier to understand at a glance. To continue the analogy, finding the empirical formula from a molecular formula is like simplifying a fraction; it boils down the molecular complexity into the most basic representation without changing the proportions.

The molecular formula describes the exact number of each type of atom in a molecule. It's more specific than the empirical formula and can be thought of as the blueprint that shows the precise number and arrangement of atoms. For example, glucose has a molecular formula of C₆H₁₂O₆, which tells you that one molecule of glucose contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.

To find the empirical formula from a molecular formula, one must find the greatest common factor that the atom counts have in common and divide them by this factor. This process is akin to simplifying a complex architectural plan into a more straightforward sketch that captures the essential design without all the intricate details.

Stoichiometry is like the recipe for a chemical reaction. It involves the calculation of the quantities of reactants and products involved in a chemical reaction. It's all based on the balanced chemical equation, which obeys the law of conservation of mass - meaning matter is neither created nor destroyed during a chemical reaction. The coefficients in a balanced equation tell us in what ratio reactants combine and products form.

Just as a recipe would say 'two eggs for every one cup of flour', stoichiometry tells you how many molecules of one substance react with another. The empirical formula plays a key role here. By knowing the simplest ratios of elements in a compound, scientists can predict and measure how compounds will behave in reactions and how much of each substance will be needed to achieve a particular outcome. This is the foundation for crafting everything from pharmaceuticals to new materials.