Properties of small molecules

This question is about structure and bonding.

Calcium sulfide is an ionic compound.

Figure 13 represents the structure of calcium sulfide.

Determine the empirical formula of calcium sulfide.

Calcium is in Group 2 of the periodic table.

Sulfur is in Group 6 of the periodic table.

Describe what happens when a calcium atom reacts with a sulfur atom.

Answer in terms of electrons and ions.

Figure 14 shows the structure of graphite.

Describe the structure and bonding of graphite.

Substances that consist of small molecules do not conduct electricity.

Give one reason why.

Methane consists of small molecules.

Poly(ethene) is a polymer.

Why does poly(ethene) have a higher melting point than methane?

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This question is about structure and bonding.

Calcium sulfide is an ionic compound.

Figure 2 represents the structure of calcium sulfide.

Determine the empirical formula of calcium sulfide.

Calcium is in Group 2 of the periodic table.

Sulfur is in Group 6 of the periodic table.

Describe what happens when a calcium atom reacts with a sulfur atom.

Answer in terms of electrons and ions.

Figure 3 shows the structure of graphite.

Describe the structure and bonding of graphite.

Substances that consist of small molecules do not conduct electricity.

Give one reason why.

Methane consists of small molecules.

Poly(ethene) is a polymer.

Why does poly(ethene) have a higher melting point than methane?

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This question is about carbon and carbon compounds.

An atom of carbon is represented as:

What is the number of protons in this atom of carbon?

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What is the number of neutrons in this atom of carbon?

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What is the number of electrons in this atom of carbon?

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Figure 10 shows the structure of a carbon compound.

Complete the formula of the carbon compound.

C__ F__

Methane:

• is a carbon compound

• exists as small molecules

• has a low boiling point.

What is the reason for the low boiling point of methane?

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Buckminsterfullerene (C₆₀) is a form of carbon.

Buckminsterfullerene was the first fullerene to be discovered.

What is the shape of a buckminsterfullerene molecule?

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Graphite is a form of carbon.

Figure 11 represents the structure of graphite.

How many covalent bonds does each carbon atom form in graphite?

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Diamond is another form of carbon.

Figure 12 represents the structure of diamond.

Describe the structure and bonding in diamond.

This question is about propane (C₃H₈).

Figure 7 shows the displayed structural formula of propane.

Explain why propane has a low boiling point.

Propane reacts with oxygen to produce carbon dioxide and water.

The reaction is exothermic.

Figure 8 shows four reaction profiles.

Which is the correct reaction profile and labels for the reaction between propane and oxygen?

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Figure 9 shows the displayed formula equation for the reaction between propane and oxygen.

The overall energy change of this exothermic reaction is 2219 kJ/mol.

Table 4 shows the bond energies of the bonds in the reaction.

Calculate the bond energy of the C — H bond (X).

This question is about hydrogen and compounds of hydrogen. Figure 3 shows the displayed formulae for the reaction between hydrogen and chlorine.

Figure 3

Table 4 shows the bond energies.

Which expression shows how to calculate the overall energy change for the reaction in Figure 3 ? Use Table 4. Tick (✓) one box.

The reaction between hydrogen and chlorine is exothermic.

Explain why this reaction releases energy to the surroundings.

Figure 4 shows part of a reaction profile for the reaction between hydrogen and chlorine. Complete the reaction profile in Figure 4. You should:

• label the activation energy

• label the overall energy change.

Draw a dot and cross diagram for a molecule of hydrogen chloride (HC l). Show the outer shell electrons only.

Figure 5 represents molecules of methane and of poly(ethene).

Methane is a gas at room temperature but poly(ethene) is a solid at room temperature.

Explain why methane and poly(ethene) exist in different states at room temperature.

This question is about carbon and its compounds.

Fullerenes are molecules of carbon atoms.

The first fullerene to be discovered was Buckminsterfullerene (C₆₀).

What shape is a Buckminsterfullerene molecule?

Give one use of a fullerene.

Propanone is a compound of carbon, hydrogen and oxygen.

Figure 13 shows the dot and cross diagram for a propanone molecule.

Complete Figure 14 to show a propanone molecule.

Use a line to represent each single bond.

Use Figure 13.

Figure 14

Determine the molecular formula of propanone.

Use Figure 13.

Propanone is a liquid with a low boiling point.

Why does propanone have a low boiling point?

Tick (✓) one box.

Figure 15 represents the structure of graphite.

Explain why graphite is:

• a good electrical conductor

• soft and slippery.

You should answer in terms of structure and bonding.

This question is about carbon and its compounds.

Fullerenes are molecules of carbon atoms. The first fullerene to be discovered was Buckminsterfullerene (C₆₀).

What shape is a Buckminsterfullerene molecule?

Give one use of a fullerene.

Propanone is a compound of carbon, hydrogen and oxygen. Figure 1 shows the dot and cross diagram for a propanone molecule.

Complete Figure 2 to show a propanone molecule. Use a line to represent each single bond. Use Figure 1.

Figure 2

Determine the molecular formula of propanone. Use Figure 1.

Propanone is a liquid with a low boiling point. Why does propanone have a low boiling point? Tick (✓) one box.

Figure 3 represents the structure of graphite.

Explain why graphite is:

• a good electrical conductor

• soft and slippery.

You should answer in terms of structure and bonding.

This question is about structure and bonding.

Which two substances have intermolecular forces between particles? Tick (✓) two boxes.

Table 5 shows the structures of three compounds.

Compare the structure and bonding of the three compounds:

• carbon dioxide

• magnesium oxide

• silicon dioxide.

This question is about Group 7 elements. Chlorine is more reactive than iodine.

Name the products formed when chlorine solution reacts with potassium iodide solution.

Explain why chlorine is more reactive than iodine.

Chlorine reacts with hydrogen to form hydrogen chloride. Explain why hydrogen chloride is a gas at room temperature. Answer in terms of structure and bonding.

Bromine reacts with methane in sunlight. Figure 9 shows the displayed formulae for the reaction of bromine with methane.

Table 3 shows the bond energies and the overall energy change in the reaction.

Calculate the bond energy X for the C^___Br bond. Use Figure 9 and Table 3.

Titanium is a transition metal. Titanium is extracted from titanium dioxide in a two stage industrial process. Stage 1 TiO₂ + 2 C + 2 Cl₂ TiCl₄ + 2 CO Stage 2 TiCl₄ + 4 Na Ti + 4 NaCl

Suggest one hazard associated with Stage 1.

Water must be kept away from the reaction in Stage 2. Give one reason why it would be hazardous if water came into contact with sodium.

Suggest why the reaction in Stage 2 is carried out in an atmosphere of argon and not in air.

Titanium chloride is a liquid at room temperature. Explain why you would not expect titanium chloride to be a liquid at room temperature.

In Stage 2, sodium displaces titanium from titanium chloride.

Sodium atoms are oxidised to sodium ions in this reaction. Why is this an oxidation reaction?

Complete the half equation for the oxidation reaction.

In Stage 2, 40 kg of titanium chloride was added to 20 kg of sodium. The equation for the reaction is:

Relative atomic masses (A_r): Na = 23 Cl = 35.5 Ti = 48 Explain why titanium chloride is the limiting reactant. You must show your working.

For a Stage 2 reaction the percentage yield was 92.3% The theoretical maximum mass of titanium produced in this batch was 13.5 kg. Calculate the actual mass of titanium produced.