Empirical Formulas and Molar Mass

The video tutorial explains how to determine empirical formulas using percentage compositions of elements. It covers converting percentages to grams, then to moles, and finally finding the smallest mole ratio to determine the empirical formula. Two examples are provided: one with sodium, oxygen, and sulfur, and another with aluminum, nitrogen, and oxygen. The tutorial emphasizes understanding the process and recognizing familiar chemical compounds.

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

• Convert percentages to moles

• Convert grams to percentages

• Convert percentages to grams

• Convert moles to grams

What is the molar mass of one mole of sodium used in the calculation?

• 16 grams

• 32.06 grams

• 14.01 grams

• 22.98 grams

How do you determine the smallest number of moles in a compound?

• By multiplying all moles by a constant

• By identifying the smallest mole value

• By dividing all moles by the largest number

• By adding all moles together

What is the empirical formula for a compound with 2 moles of sodium, 3 moles of oxygen, and 1 mole of sulfur?

• Na3O2S

• Na2SO3

• Na2O3S

• NaO2S3

What is the charge on the sulfite ion in sodium sulfite?

• Positive two

• Positive one

• Negative two

• Negative one

In the new example, what is the first element's percentage composition converted to grams?

• 26.98 grams of aluminum

• 67.60 grams of oxygen

• 19.73 grams of nitrogen

• 12.67 grams of aluminum

What is the molar mass of one mole of aluminum used in the calculation?

• 14.01 grams

• 12.67 grams

• 32.06 grams

• 26.98 grams

What is the correct empirical formula for a compound with 1 aluminum, 3 nitrogen, and 9 oxygen atoms?

• AlN3O9

• Al(NO3)3

• Al(NO2)3

• Al3N9O

Why is the simplified form of aluminum nitrate more recognizable?

• It has fewer atoms

• It is in a form that can be easily named

• It is more complex

• It has a higher charge

What is the final empirical formula for the compound with aluminum, nitrogen, and oxygen?

• Al3N9O

• Al(NO3)3

• Al(NO2)3

• AlN3O9