Empirical and Molecular Formulas

This video tutorial explains how to determine the molecular formula of a compound using its empirical formula and relative molecular mass. It provides two example problems: one involving phosphorus and oxygen, and another with carbon, hydrogen, and oxygen. The tutorial guides viewers through calculating the empirical formula, determining the ratio of elements, and using the relative molecular mass to find the molecular formula.

What is the purpose of using the empirical formula and relative molecular mass in chemistry?

• To determine the color of a compound

• To find the molecular formula of a compound

• To measure the boiling point of a compound

• To calculate the density of a compound

In the first example, what is the empirical formula of the compound containing phosphorus and oxygen?

• P2O3

• P2O5

• P6O15

• P4O10

How do you determine the ratio of elements in an empirical formula?

• By dividing the percentages by the smallest number

• By adding the atomic numbers

• By subtracting the atomic masses

• By multiplying the atomic masses

What is the relative molecular mass of the empirical formula P2O5?

• 142 grams per mole

• 284 grams per mole

• 180 grams per mole

• 30 grams per mole

In the first example, what is the molecular formula of the compound?

• P4O10

• P2O5

• P6O15

• P8O20

In the second example, what is the empirical formula of the compound containing carbon, hydrogen, and oxygen?

• C3H6O3

• C6H12O6

• CH2O

• C2H4O2

What is the relative molecular mass of the empirical formula CH2O?

• 30 grams per mole

• 60 grams per mole

• 180 grams per mole

• 90 grams per mole

In the second example, what is the molecular formula of the compound?

• C2H4O2

• C12H24O12

• C6H12O6

• C3H6O3

How do you calculate the molecular formula from the empirical formula?

• By dividing the relative molecular mass by the atomic number

• By multiplying the empirical formula by the ratio of the molecular mass to the empirical mass

• By adding the atomic masses of all elements

• By subtracting the empirical mass from the molecular mass

What is the significance of the empirical formula in chemistry?

• It determines the boiling point of a compound

• It indicates the color of a compound

• It provides the simplest whole number ratio of elements in a compound

• It shows the exact number of atoms in a molecule