MCAT General Chemistry: Percent by Mass Composition

What is the general rule for calculating any percentage?

• Part over whole times 100

• Whole over part times 100

• Whole times part times 100

• Part times whole times 100

In the pizza analogy, if you eat 3 slices out of 12, what percentage of the pizza have you consumed?

• 30%

• 20%

• 35%

• 25%

When calculating the percent composition of chlorine in NaCl, what is the molar mass of NaCl used?

• 60 grams per mol

• 58 grams per mol

• 35 grams per mol

• 23 grams per mol

What is the approximate percent composition of chlorine in NaCl?

• 60%

• 58%

• 50%

• 65%

Why is it important to understand empirical formulas when calculating percent composition?

• They are used to calculate the density of a compound.

• They are always larger than molecular formulas.

• They provide the exact mass of the compound.

• They simplify the ratio of elements in a compound.

What is the empirical formula of glucose?

• C6H12O6

• CH2O

• C2H4O2

• C3H6O3

How do you convert a decimal to a percentage?

• Divide by 100

• Multiply by 10

• Multiply by 100

• Add 100

What is the percent composition of carbon in glucose using the empirical formula?

• 30%

• 60%

• 40%

• 50%

What is the percent composition of hydrogen in glucose using the empirical formula?

• 5%

• 7%

• 12%

• 10%

What is the percent composition of oxygen in glucose using the empirical formula?

• 40%

• 45%

• 50%

• 55%