Empirical and Molecular Formulas

This video tutorial covers the process of determining empirical formulas from mass percent composition and combustion analysis. It explains the concept of empirical formulas, how to simplify molecular formulas, and the steps to calculate empirical formulas using mass data. The tutorial also delves into combustion analysis, demonstrating how to find empirical formulas for compounds containing carbon, hydrogen, and oxygen. The video provides examples and tips for handling non-whole number ratios in empirical formulas.

What is the empirical formula of a compound with a molecular formula of C6H12O6?

• C6H12O6

• C3H6O3

• C2H4O2

• CH2O

If you have 20 grams of carbon, how many moles of carbon do you have?

• 2.00 moles

• 1.67 moles

• 2.50 moles

• 1.50 moles

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

• Subtract the empirical mass from the molecular mass

• Add the molecular mass to the empirical mass

• Divide the subscripts by the ratio of molecular mass to empirical mass

• Multiply the subscripts by the ratio of molecular mass to empirical mass

What is the molecular formula if the empirical formula is CH2 and the molar mass is 56 g/mol?

• C2H4

• C3H6

• C4H8

• C5H10

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

• Convert percent to grams

• Convert grams to moles

• Find the molecular formula

• Balance the chemical equation

What is the empirical formula of a compound with 81.8% carbon and 18.2% hydrogen?

• C1H2

• C2H5

• C3H8

• C4H10

How do you adjust a mole ratio of 2.67 to a whole number?

• Multiply by 3

• Multiply by 5

• Multiply by 2

• Multiply by 4

In a combustion analysis, what is the relationship between moles of carbon in CO2 and the original compound?

• The compound has more moles

• CO2 has twice the moles

• They are equal

• They are unrelated

In combustion analysis, why can't you find the moles of oxygen directly from CO2 and H2O?

• Oxygen is only in CO2

• Oxygen from air is also present in CO2 and H2O

• Oxygen is only in H2O

• Oxygen is not present in the compound

What is the empirical formula of a compound with 1.75 moles of carbon, 2.25 moles of hydrogen, and 1 mole of oxygen?

• C7H9O4

• C5H7O3

• C6H8O3

• C8H10O5