Moles & amount of substance

Buckminsterfullerene is a form of carbon.

Buckminsterfullerene is a covalent molecule that consists of 60 carbon atoms.

Describe the structure of a buckminsterfullerene molecule.

Calculate the number of molecules in 9.00 g of buckminsterfullerene (C₆₀).

Relative atomic mass (A_r): C = 12

The Avogadro constant = 6.02 × 10²³ per mole

This question is about acids and salts.

Nitric acid is a strong acid.

A solution of nitric acid can be dilute.

Explain how nitric acid can be both strong and dilute.

The pH value of a solution of nitric acid increases by 1.

How does the hydrogen ion concentration of the solution change?

Tick (✓) one box.

Decreases by a factor of 10

Decreases by a factor of 100

Increases by a factor of 10

Increases by a factor of 100

Question 8 continues in the next page

A student reacted nitric acid with excess calcium carbonate.

The word equation for the reaction is:

calcium carbonate + nitric acid calcium nitrate + water + carbon dioxide

This is the method used.

1. Measure 100 cm³ of nitric acid into a beaker.

2. Add calcium carbonate powder to the nitric acid.

3. Stir the mixture.

4. Repeat steps 2 and 3 until the calcium carbonate is in excess.

5. Filter the mixture.

Describe the additional steps that should be included in the method to determine the mass of calcium carbonate that reacted.

The formula of nitric acid is HNO₃

Which expression gives the percentage (%) by mass of oxygen in HNO₃?

Relative atomic mass (A_r): O = 16

Relative formula mass (M_r): HNO₃ = 63

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What is the formula of calcium nitrate?

Use the periodic table.

Tick (✓) one box.

CaNO₃

Ca(NO₃)₂

Ca₂NO₃

Ca₂(NO₃)₃

Question 8 continues in the next page

Magnesium chloride is a salt.

Calculate the number of magnesium ions in 47.5 g of magnesium chloride (MgCl₂).

Relative atomic masses (A_r): Mg = 24 Cl = 35.5

Avogadro constant = 6.02 × 10²³ per mole

This question is about chemical quantities.

0.40 dm³ of a solution contains 48.4 g of solute.

Calculate the concentration of the solution.

Give the unit.

Calculate the number of carbon dioxide molecules in 3.00 moles of carbon dioxide.

The Avogadro constant = 6.02 × 10²³ per mole.

Give your answer to 3 significant figures.

Metal M forms a metal oxide with the formula M₂O₃

The relative formula mass of the metal oxide is 152.

Determine the identity of metal M.

Relative atomic mass (A_r): O = 16

Copper oxide reacts with sulfuric acid to produce copper sulfate.

What type of substance is copper oxide?

Tick (✓) one box.

Acid

Alkali

Base

Salt

A student produced a pure, dry sample of copper sulfate crystals.

This is the first part of the method.

1. Measure 100 cm³ of sulfuric acid into a beaker.

2. Gently warm the sulfuric acid.

3. Add 1.0 g of copper oxide powder to the sulfuric acid.

4. Stir the mixture.

5. Repeat steps 3 and 4 until the copper oxide is in excess.

6. Filter the mixture.

Describe the additional steps needed to produce a pure, dry sample of copper sulfate crystals.

The student added excess copper oxide.

Describe the steps that the student could include in the method to find the mass of copper oxide that reacted.

The student found that 2.4 g of copper oxide had reacted.

Copper oxide (CuO) is an ionic compound.

Calculate the total number of ions in 2.4 g of copper oxide.

Relative atomic masses (A_r): Cu = 63.5 O = 16

The Avogadro constant = 6.02 × 10²³ per mole

This question is about halogens.

Bromine reacts with sodium to produce sodium bromide.

Describe the structure of and bonding in sodium bromide.

The equation for the reaction is:

1 g of bromine reacts with sodium.

Calculate the number of bromine molecules in 1 g of bromine.

1 mole of bromine contains 6.02 × 10²³ bromine molecules.

Relative formula mass (M_r) of bromine = 160

Table 5 shows the boiling points of some halogens.

Explain the trend in the boiling points of the halogens.

A 1 kg mass is made from a platinum and iridium alloy.

The platinum and iridium alloy is harder than pure platinum.

Explain why alloys are harder than the pure metal.

The 1 kilogram mass consisted of 900 g platinum and 100 g iridium.

What was the ratio of platinum atoms to iridium atoms in the alloy?

Relative atomic masses (A_r): Pt = 195
Ir = 192

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The Avogadro constant is the number of atoms in 1 mole of a substance.

What is the value of the Avogadro constant?

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Scientists could use a sample of silicon to define the Avogadro constant.

Copper is an impurity in the silicon sample.

There are 70 nanograms of copper in 1 g of the sample.

Calculate the mass of copper in grams in 1 kg of the sample.

Give your answer in standard form.

1 nanogram = 10^–9 g

Silicon mainly occurs in the Earth’s crust as silicon dioxide.

Figure 8 represents part of the structure of silicon dioxide.

Determine the empirical formula of silicon dioxide.

Use Figure 8.

Describe the structure and bonding in silicon dioxide.

Copper can be extracted using biological methods.

Name two biological methods used to extract copper from copper ores.

For each method, name the type of organism used in the process.

Give three reasons why biological methods are being introduced to extract copper.

The biological methods produce copper compounds such as copper sulfate.

Copper can be extracted from copper sulfate solution by adding scrap iron.

Explain why.

Complete the chemical equation for the reaction between iron and copper sulfate solution.

Include state symbols.

A solution of copper sulfate contains 3.175 g of copper ions.

Calculate the number of copper ions in the solution.

Give your answer in standard form.

Relative atomic mass (A_r): Cu = 63.5

The Avogadro constant is 6.02 × 10²³ per mole.