Empirical vs Molecular Formulas: Calculating Composition and Ratios in Compounds

This video tutorial explains the difference between empirical and molecular formulas. It covers how to calculate the empirical formula from percentage composition by mass and how to derive the molecular formula from the empirical formula. The tutorial uses the compound hydrazine as an example, demonstrating the step-by-step process of finding the simplest ratio of atoms and calculating the molecular formula using the empirical mass.

What is the primary difference between an empirical formula and a molecular formula?

• Molecular formula shows the types of bonds.

• Empirical formula shows the exact number of atoms.

• Empirical formula shows the simplest ratio of atoms.

• Molecular formula shows the simplest ratio of atoms.

In the molecular formula of hydrazine (N2H4), how many hydrogen atoms are present?

• Two

• Four

• Six

• Eight

What does the empirical formula of a compound indicate?

• The exact number of each type of atom.

• The types of bonds in the compound.

• The simplest ratio of each type of atom.

• The molecular weight of the compound.

If a compound has 87.5% nitrogen and 12.5% hydrogen by mass, what is the empirical formula?

• NH

• NH2

• NH3

• N2H4

What is the first step in calculating the empirical formula from percentage composition?

• Divide percentages by atomic masses.

• Multiply percentages by atomic masses.

• Add percentages together.

• Subtract percentages from 100.

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

• Add the empirical formula to the molecular mass.

• Multiply the empirical formula by a factor n.

• Divide the molecular mass by the empirical mass.

• Multiply the empirical formula by the atomic number.

What is the empirical mass of NH2?

• 18

• 16

• 14

• 20

If the molecular mass is 32 and the empirical mass is 16, what is the value of n?

• 4

• 2

• 1

• 3

What does the molecular formula of a compound reveal?

• The types of atoms and their exact number.

• The molecular weight and density.

• The types of bonds and their strength.

• The types of atoms and their simplest ratio.

What is the molecular formula of a compound with an empirical formula of NH2 and n=2?

• NH2

• N2H2

• N2H4

• NH4