Test – Moles

Define the term ‘mole’ and state the value of Avogadro’s constant.

Calculate the number of moles in:

1. 24.0g of magnesium (Mg)
2. 6.0g of carbon (C)
3. 4.0g of sodium hydroxide (NaOH)

Calculate the mass of:

1. 0.5 moles of oxygen gas (O₂)
2. 0.25 moles of calcium carbonate (CaCO₃)
3. 0.01 moles of potassium permanganate (KMnO₄)

Calculate the volume (at room temperature and pressure) of:

1. 0.75 moles of hydrogen gas (H₂)
2. 0.125 moles of carbon dioxide (CO₂)

Calculate the percentage by mass of:

1. Hydrogen in ammonia (NH₃)
2. Oxygen in calcium carbonate (CaCO₃)

Zinc reacts with hydrochloric acid according to the equation: Zn + 2HCl → ZnCl₂ + H₂

Calculate:

1. The mass of zinc needed to produce 12 dm³ of hydrogen gas at RTP
2. The volume of hydrogen gas produced when 6.5g of zinc fully reacts with excess acid

9.0g of aluminum reacts with 9.6g of oxygen to form aluminum oxide.

The equation for the reaction is: 4Al + 3O₂ → 2Al₂O₃

1. Calculate the number of moles of aluminum present
2. Calculate the number of moles of oxygen present
3. Identify the limiting reactant and explain your answer
4. Calculate the mass of aluminum oxide produced

A 0.25g sample of impure copper carbonate, CuCO₃, was heated strongly to produce copper oxide, carbon dioxide, and water vapor. The copper oxide formed weighed 0.16g.

1. Write a balanced equation for the decomposition of copper carbonate
2. Calculate the mass of pure copper carbonate in the original sample
3. Calculate the percentage purity of the original copper carbonate sample

Which two of the following contain the same number of atoms? Show your calculations.

1. 2.0g of hydrogen gas (H₂)
2. 16.0g of oxygen gas (O₂)
3. 14.0g of nitrogen gas (N₂)
4. 4.0g of helium (He)

The reaction between sodium thiosulfate and hydrochloric acid can be represented by the equation:

Na₂S₂O₃ + 2HCl → 2NaCl + SO₂ + S + H₂O

What volume of sulfur dioxide gas at RTP would be produced when 12.4g of sodium thiosulfate reacts with excess hydrochloric acid?