Empirical and Molecular Formulas from Percent Composition in Chemistry

This video tutorial explains how to determine the empirical and molecular formulas of a compound. It covers calculating the empirical formula from percent composition and given masses, and deriving the molecular formula using the empirical formula and molar mass. The tutorial provides step-by-step instructions and examples to illustrate the process.

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

• Convert percent to grams

• Convert grams to liters

• Convert grams to percent

• Convert moles to grams

How do you determine the smallest number of moles when calculating the empirical formula?

• By comparing the percent composition

• By comparing the atomic numbers

• By comparing the molar masses

• By comparing the calculated moles of each element

What is the empirical formula for a compound with 52.14% carbon, 13.13% hydrogen, and 34.73% oxygen?

• C3H8O

• C2H6

• CH3O

• C2H6O

What is the next step after finding the empirical formula to determine the molecular formula?

• Determine the boiling point of the compound

• Calculate the percent composition

• Find the molar mass of the empirical formula

• Calculate the density of the compound

How do you find the factor to multiply the empirical formula to get the molecular formula?

• Divide the molar mass of the empirical formula by the molar mass of the compound

• Multiply the molar mass of the compound by the molar mass of the empirical formula

• Add the molar masses of the compound and empirical formula

• Divide the molar mass of the compound by the molar mass of the empirical formula

What is the empirical formula for a compound with 20.32 grams of carbon, 5.12 grams of hydrogen, and 7.9 grams of nitrogen?

• C4H10N

• CH4N

• C3H9N

• C2H5N

How do you convert grams of an element to moles?

• Divide by the atomic number

• Divide by the atomic mass

• Multiply by the atomic number

• Multiply by the atomic mass

What is the molecular formula for a compound with an empirical formula of C3H9N and a molar mass of 236.448 g/mol?

• C3H9N

• C12H36N4

• C9H27N3

• C6H18N2

What is the purpose of dividing the molar mass of the molecular formula by the molar mass of the empirical formula?

• To find the density of the compound

• To determine the number of empirical units in the molecular formula

• To calculate the boiling point

• To find the percent composition

What is the final step in determining the molecular formula from the empirical formula?

• Divide the subscripts of the empirical formula by the determined factor

• Subtract the atomic masses of all elements

• Multiply the subscripts of the empirical formula by the determined factor

• Add the atomic masses of all elements