Empirical Formulae From Percentage Composition

The video tutorial explains the difference between empirical and molecular formulas, using hydrazine as an example. It details how to calculate the empirical formula from percentage composition by mass and how to derive the molecular formula from the empirical formula. The tutorial provides a step-by-step guide to these calculations, emphasizing the importance of understanding the types and ratios of atoms in a compound. The video concludes with a recap of the key points about molecular and empirical formulas.

What does the molecular formula of a compound indicate?

• The types of atoms and their simplest ratio

• The simplest ratio of atoms only

• The types of atoms only

• The types of atoms and their exact number

How is the simplest ratio of atoms in a compound determined?

• By comparing the molecular and empirical formulas

• By dividing the number of each type of atom by their greatest common divisor

• By dividing the molecular formula by 2

• By analyzing the types of atoms

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

• Divide the percentages by the relative atomic mass

• Add the percentages together

• Convert percentages to decimals

• Multiply the percentages by the atomic mass

What is the empirical formula of a compound with 87.5% nitrogen and 12.5% hydrogen?

• NH3

• NH2

• N2H4

• NH

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

• Multiply the empirical formula by the atomic mass

• Divide the molecular mass by the empirical mass and multiply the empirical formula by this number

• Add the empirical formula to the molecular mass

• Subtract the empirical mass from the molecular mass