Moles Practice

What is the gram formula mass of Mg(ClO₃)₂?

• 107 g

• 142 g

• 174 g

• 191 g

What is the percent composition by mass of

oxygen in Ca(NO₃)₂ (molar mass=164 g/mol)?

• 75%

• 59%

• 48%

• 29%

How many moles are in 168 g of KOH? (molar mass = 56 g)

• 0.3 mol

• 0.5 mol

• 1.0 mol

• 3.0 mol

What is the total number of molecules of hydrogen in 0.25 mole of hydrogen? (molar mass = 2.0 g/mol)

• 6.0 × 10²³

• 4.5 × 10²³

• 3.0 × 10²³

• 1.5 × 10²³

What is the volume of 1.50 moles of an N₂ gas at STP? (molar mass = 28.0 g/mol)

• 11.2 L

• 22.4 L

• 33.6 L

• 44.8 L

What is the total number of atoms contained in 80. grams of neon? (molar mass = 20.7 g/mol)

• 6.0 × 10²³

• 1.2 × 10²⁴

• 2.4 × 10²⁴

• 4.8 × 10²⁴

A student determining the percent by mass of water in a hydrated sample of salt obtained the following data:

Mass of hydrate before heating 6.25 g

Mass of sample after 1st heating 5.12 g

Mass of sample after 2nd heating 5.12 g

The correct expression for obtaining the percent by mass of water in the sample is

The theoretical percent by mass of water in the hydrate Na₂SO₄•10H₂O is closest to

• 18%

• 44%

• 56%

• 76%