Grade 9

What is the percent by mass of magnesium in MgO?

• 20%

• 40%

• 50%

• 60%

What is the percent by mass of chlorine in NaCl?

• 39%

• 61%

• 35%

• 35%

What is the percent by mass of fluorine in CaF₂ (gram-formula mass = 78 g/mol)?

• 24%

• 49%

• 49%

• 65%

What is the percent by mass of calcium in CaF₂ (gram-formula mass = 78 g/mol)?

• 24%

• 49%

• 51%

• 65%

Find the percent composition of Cu₂S?

• %Cu= 67.987 %S= 32.013

• %Cu= 79.854 %S= 20.145

• %Cu= 35.946 %S= 64.054

What is the percent composition of Benzene, C₆H₆?

• C = 50%

  H = 50%

• C = 85.7 %

  H = 14.3%

• C = 92.2%

  H = 7.8%

• C = 71.9%

  H = 28.1%

Which element in the compound potassium cyanide, KCN, has a percent composition of 60.97%?

• K

• C

• N

• None

What is the mass of one mole of aluminum chloride (remember to determine the correct formula first)?

• 62.435g

• 116.399g

• 133.341g

• 97.888g

Which of the following is NOT needed to calculate percent composition?

• Mass of specific element

• Molar Mass

• Avogadro's Number

• Division

The molar mass of an element is equal to its...

• Atomic mass

• Atomic number

• Oxidation number

• Valence electrons