Mole Math + Empirical and Molecular Formulas + % Composition

Front

What is Avogadro's number?

Back

Avogadro's number is 6.022 x 10^23, which is the number of atoms, molecules, or formula units in one mole of a substance.

Front

How do you calculate the number of atoms in a given number of moles?

Back

Multiply the number of moles by Avogadro's number (6.022 x 10^23).

Front

What is the formula to find the mass of a substance in grams from moles?

Back

Mass (g) = Moles x Molar Mass (g/mol).

Front

Define empirical formula.

Back

An empirical formula is the simplest whole number ratio of elements in a compound.

Front

What is a molecular formula?

Back

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

Front

How do you determine the empirical formula from percent composition?

Back

Convert the percentages to grams, then to moles, and find the simplest whole number ratio.

Front

What is the % composition of an element in a compound?

Back

% Composition = (mass of element in 1 mole of compound / molar mass of compound) x 100.

Front

Calculate the number of molecules in 1 mole of water (H₂O).

Back

1 mole of water contains 6.022 x 10^23 molecules.

Front

What is the molar mass of xenon (Xe)?

Back

The molar mass of xenon is approximately 131.29 g/mol.

Front

If a compound has 30.40% nitrogen and 69.60% oxygen, what is its empirical formula?

Back

The empirical formula is NO₂.