How To calculate Percentage Mass

This video tutorial explains how to calculate the percent mass of elements within a chemical formula, using water as an example. It covers the basics of chemical formulas, the concept of molar mass, and the step-by-step process to determine the percent mass of hydrogen and oxygen in water. The tutorial also includes a challenge to calculate the percent mass of oxygen and summarizes the method for any chemical formula.

What does the chemical formula H2O indicate about the composition of water?

• Two oxygen atoms for every hydrogen atom

• Two hydrogen atoms for every oxygen atom

• Equal number of hydrogen and oxygen atoms

• One hydrogen atom for every two oxygen atoms

How is the molar mass of water calculated?

• By adding the atomic masses of two oxygen atoms

• By multiplying the atomic mass of hydrogen by three

• By subtracting the atomic mass of oxygen from hydrogen

• By adding the atomic masses of two hydrogen atoms and one oxygen atom

What is the percentage mass of hydrogen in water?

• 33.3%

• 50%

• 11.1%

• 88.9%

How can you calculate the percent mass of oxygen in water?

• By subtracting the percent mass of hydrogen from 100%

• By adding the percent mass of hydrogen to 100%

• By dividing the percent mass of hydrogen by 2

• By multiplying the percent mass of hydrogen by 2

What is the general formula for calculating mass percent of an element in a compound?

• Total mass of compound multiplied by mass of element, divided by 100

• Mass of element multiplied by total mass of compound, divided by 100

• Total mass of compound divided by mass of element, multiplied by 100

• Mass of element divided by total mass of compound, multiplied by 100