Understanding Relative Formula Mass and Percentage Composition

What does the relative atomic mass of an element represent?

• The mass of the most common isotope

• The number of protons in the element

• The average mass of all isotopes of the element

• The mass of the element's nucleus

How do you calculate the relative formula mass of a compound?

• By dividing the total mass by the number of elements

• By adding the number of protons in each element

• By adding the relative atomic masses of all atoms in the compound

• By multiplying the atomic numbers of all elements

What is the relative formula mass of magnesium chloride (MgCl2)?

• 71

• 95

• 84

• 59

How do you find the percentage mass of an element in a compound?

• By dividing the element's atomic number by the compound's mass

• By multiplying the element's relative atomic mass by the number of its atoms and dividing by the compound's relative formula mass

• By adding the element's atomic mass to the compound's mass

• By subtracting the element's mass from the compound's mass

What is the percentage mass of oxygen in calcium hydroxide (Ca(OH)2)?

• 32.7%

• 43.2%

• 50.0%

• 25.0%