Empirical and Molecular Formulas

This video tutorial explains the difference between empirical and molecular formulas. It provides step-by-step instructions on how to calculate the empirical formula from percentage composition and how to determine the molecular formula using the empirical formula and molecular weight. The tutorial includes two example problems to illustrate these calculations.

What is the main difference between empirical and molecular formulas?

• Empirical formula shows the actual number of atoms, while molecular formula shows the simplest ratio.

• Empirical formula shows the simplest ratio of elements, while molecular formula shows the actual number of atoms.

• Both show the actual number of atoms.

• Both show the simplest ratio of elements.

In the example with sulfur and oxygen, what is the empirical formula derived?

• S2O3

• SO3

• SO2

• S3O2

If the empirical formula is SO3, what is the ratio of sulfur to oxygen?

• 2:3

• 1:3

• 3:1

• 1:2

What is the atomic weight of oxygen used in the calculations?

• 32

• 35.5

• 16

• 12

In the example with sulfur and oxygen, what is the percentage of sulfur by mass?

• 30%

• 60%

• 40%

• 50%

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

• Subtract atomic weights

• Add atomic weights

• Multiply by atomic weight

• Divide by atomic weight

In the example with carbon, hydrogen, and chlorine, what is the empirical formula obtained?

• C2H5Cl

• C4H9Cl

• C3H7Cl

• CH3Cl

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

• By dividing the molecular mass by the empirical formula mass

• By adding atomic weights

• By multiplying atomic weights

• By subtracting atomic weights

What is the molecular formula if the empirical formula is C4H9Cl and the molecular mass is 184.9 g/mol?

• C8H18Cl2

• C4H9Cl

• C2H5Cl

• C6H12Cl2

What is the empirical formula mass of C4H9Cl?

• 100 g/mol

• 46.25 g/mol

• 184.9 g/mol

• 92.5 g/mol