Chemical and Empirical Formulas

Vocabulary practice flashcards defining chemical and empirical formulas, their formation and calculation rules, and specific empirical formulas of substances.

Chemical Formula

A representation of a chemical substance using alphabets to represent the atoms and subscript numbers to show the number of each type of atoms found in the elementary entities of the substance.

Sulphuric acid

A compound with the chemical formula $H_2SO_4$, consisting of 2 hydrogen atoms, 1 sulphur atom, and 4 oxygen atoms.

Iron(III) chloride

A chemical compound with the formula $FeCl_3$, formed when one iron(III) ion ($Fe^{+3}$) with three positive charges is balanced and neutralised by three chlorine ions ($Cl^-$), each carrying one negative charge, resulting in an overall charge equal to zero.

Empirical Formula

The chemical formula that shows the simplest ratio of the number of atoms of each element in a compound.

Steps in Determining the Empirical Formula of a Compound

The four-step process: 1. Determine the mass of each element; 2. Determine the number of mole; 3. Simplify the number of mol using the same factor; 4. Multiply the number of mole with a factor to get an integer.

Empirical Formula Calculation ($C_4H_9$ Example)

A calculation where $96\,g$ of carbon ($\frac{96}{12} = 8\text{ mol}$) and $18\,g$ of hydrogen ($\frac{18}{1} = 18\text{ mol}$) produce a mole ratio of $8:18$, simplifying to the simplest mole ratio of $4:9$ ($\frac{8}{2} = 4$ and $\frac{18}{2} = 9$), yielding $C_4H_9$.

Hydrazine (Empirical Formula)

$$NH_2$$

Propene (Empirical Formula)

$$CH_2$$

Benzene (Empirical Formula)

$$CH$$

Water (Empirical Formula)

$$H_2O$$

Ammonia (Empirical Formula)

$$NH_3$$