Percent Composition and Molar Mass

This video tutorial explains how to find the percent composition by mass for each element in potassium hydroxide (KOH). It begins with calculating the molar mass of the compound and then proceeds to determine the percent composition of potassium, oxygen, and hydrogen. Each element's contribution to the total mass is calculated and expressed as a percentage. The tutorial concludes by summarizing the process and results.

What is the main focus of the video tutorial?

• Learning about the history of KOH

• Finding the percent composition by mass for each element in KOH

• Calculating the density of KOH

• Understanding the chemical reactions of KOH

What is the first step in finding the percent composition by mass?

• Identifying the number of atoms in the compound

• Calculating the molar mass of the compound

• Measuring the volume of the compound

• Balancing the chemical equation

How is the molar mass of a compound expressed?

• In moles per gram

• In grams per liter

• In grams per mole

• In liters per mole

What is the percent composition by mass of potassium in KOH?

• 69.68%

• 56.11%

• 1.80%

• 28.52%

What is the atomic mass of potassium used in the calculation?

• 1.01

• 39.10

• 56.11

• 16.00

What is the percent composition by mass of oxygen in KOH?

• 69.68%

• 28.52%

• 1.80%

• 39.10%

Why are the units grams per mole not written for oxygen in the calculation?

• Because they are not needed for oxygen

• Because they are too large

• Because they cancel out

• Because they are irrelevant

What is the percent composition by mass of hydrogen in KOH?

• 39.10%

• 28.52%

• 1.80%

• 69.68%

What should the sum of the percent compositions of all elements in KOH be?

• 100%

• 50%

• 90%

• 75%

What is the significance of the percent composition by mass?

• It shows the contribution of each element to the total mass

• It helps in determining the volume of the compound

• It is used to calculate the density of the compound

• It is used to find the boiling point of the compound