Moles + Stoichiometry

Mole

A unit used to measure the amount of a substance, defined as containing exactly 6.022 x 10²³ entities (atoms, molecules, ions, etc.).

Molar Mass

The mass of one mole of a substance, typically expressed in grams per mole (g/mol), calculated by summing the atomic masses of all atoms in its formula.

Avogadro's Number

The number of particles in one mole of a substance, approximately 6.022 x 10²³.

Empirical Formula

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

Molecular Formula

A chemical formula that shows the actual number of atoms of each element in a molecule of a compound.

Conversion from grams to moles

To convert grams to moles, divide the mass of the substance by its molar mass.

Conversion from moles to grams

To convert moles to grams, multiply the number of moles by the molar mass of the substance.

Percent Composition

The percentage by mass of each element in a compound, calculated by dividing the mass of the element by the total molar mass of the compound.

How do you calculate empirical formula?

1. Convert mass to moles (assume that you have 100g so you can use the percentage composition)

2. Divide by smallest mole value.

3. Multiply by a factor if needed to make whole numbers.

How do you calculate molecular formula?

1. Find the empirical formula, then its molecular mass

2. factor = molecular mass given divided my empirical formula mass

3. Multiply the empirical formula by the factor

What is used as the standard reference for the relative atomic mass scale

Isotope Carbon-12

Information card (mole 2)

moles=number of particles/Avagardo's number

Information card (mole 1)

moles = mass/molar mass

Information card (percentage comp)

percentage = molecular mass of element/total mass of compound, multiplied by 100