Percentage Composition

Question 1

Formula for Mass Percent

Answer 1

Mass of element in compound divided by mass of the compound, x 100

Question 2

Law of Definite Proportions

Answer 2

*t! A compound always contains the same proportion of elements by mass
evenif mass changes, percentages stay the same

Question 3

Law of Definite Proportions: Quantity of compound is unknown

Answer 3

• Use molar mass to find the mass of each element and the compound per 1 mole
  Then divide using formula
• All percents should add to 100
• Units do not matter as they will cancel out in formula

Question 4

Percentage Composition connected to Technology, Society and the Real World

Answer 4

• Helps to identify chemicals (through empirical and molecular formula)
• Helps to synthesize chemicals in the lab due to fixed ratios
• Medicinal drugs, vitamins, household detergent
• Helps to extract elements from a compound
• As most metals are not found as pure elements
• How much percentage to take out to get metal in compound