Calculating Percent Composition by Mass

This video tutorial explains how to calculate percent composition by mass, also known as percent by mass. It covers the formula used for these calculations, which involves dividing the total molar mass of an element by the molar mass of the entire compound and multiplying by 100%. The tutorial includes examples for calculating the percent composition of hydrogen in water (H2O), iron in iron(III) chloride (FeCl3), and carbon in a compound (C6H10O4). Each example demonstrates the step-by-step process of determining the molar masses and performing the calculations.

What does percent composition by mass measure in a compound?

• The number of molecules of each element

• The mass of each element as a percentage of the total mass

• The volume of each element compared to the total volume

• The density of each element in the compound

What is the first step in calculating the percent composition by mass of an element in a compound?

• Multiply the molar mass of the element by 100%

• Divide the molar mass of the element by the molar mass of the compound

• Add the molar masses of all elements in the compound

• Subtract the molar mass of the element from the molar mass of the compound

What does the calculation of percent composition by mass involve?

• Adding the molar masses of all elements and dividing by 100

• Dividing the molar mass of the element by the total molar mass and multiplying by 100

• Subtracting the molar mass of the element from the total molar mass

• Multiplying the molar mass of the element by 100 and dividing by the molar mass of the compound

How do you calculate the molar mass of water (H2O)?

• Subtract the molar mass of oxygen from hydrogens

• Multiply the molar masses of hydrogen and oxygen

• Add the molar masses of two hydrogens and one oxygen

• Divide the molar mass of oxygen by two hydrogens

What is the percent composition by mass of hydrogen in H2O?

• 11.2%

• 88.8%

• 50%

• 18.02%

What is the molar mass of iron used in the calculation for FeCl3?

• 35.45

• 18.02

• 55.85

• 162.2

What is the percent composition by mass of iron in FeCl3?

• 55.85%

• 65.57%

• 100%

• 34.43%

How many carbons are considered in the calculation for the compound C6H10004?

• Four

• One

• Ten

• Six

What is the total molar mass of the compound C6H10004?

• 72.06

• 146.2

• 100

• 12.01

What is the percent composition by mass of carbon in C6H10004?

• 12.01%

• 49.29%

• 50.71%

• 100%