Giant Covalent Structures (Cambridge (CIE) O Level Chemistry): Exam Questions

The following table gives information about six substances.

Which substance could be a metal?

State all the substances that are liquid at room temperature.

Which substance could have a giant covalent structure similar to that of silicon(IV) oxide?

Which substance could be propane?

Which substance could be sodium chloride?

Carbon dioxide and silicon(IV) oxide are oxides of Group IV elements.

Complete the following table.

i) Name the type of bonds that exist between the atoms in silicon(IV) oxide.

 [1]

ii) Explain why silicon(IV) oxide has a very high melting point.

[1]

iii) Explain, in terms of attractive forces between particles, why carbon dioxide has a very low melting point.

[1]

iv) Explain, in terms of particles, why carbon dioxide is a non-conductor of electricity.

 [1]

i) Name the type of chemical reaction in which carbon dioxide is produced from fossil fuels.

 [1]

ii) Name the chemical process in which green plants convert carbon dioxide into carbohydrates.

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Carbon and silicon are elements in Group IV. They both form oxides of the type XO₂

Silicon(IV) oxide, SiO₂, has a giant covalent structure.

i) Describe the structure of silicon(IV) oxide

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ii) State three properties which silicon(IV) oxide and diamond have in common.

[3]

iii) How could you show that silicon(IV) oxide is acidic and not basic or amphoteric?

[2]

Explain why the physical properties of carbon dioxide are different from those of diamond and silicon(IV) oxide.

Germanium is an element in Group IV. The electron distribution of a germanium atom is 2 + 8 + 18 + 4. It has oxidation states of +2 and +4.

Germanium forms a series of saturated hydrides similar to the alkanes.

i) Draw the structural formula of the hydride which contains three germanium atoms per molecule.

[1]

ii) Predict the general formula of the germanium hydrides.

[1]

Draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound germanium(IV) chloride, GeCl₄.

Use o to represent an electron from a chlorine atom.

Use x to represent an electron from a germanium atom.

Describe the structure of the giant covalent compound germanium(IV) oxide, GeO₂. It has a similar structure to that of silicon(IV) oxide.

Is the change GeCl₂ to GeCl₄ reduction, oxidation or neither? Give a reason for your choice.

The first three elements in Group IV are carbon, silicon and germanium. The elements and their compounds have similar properties.

The compound, silicon carbide, has a giant covalent structure similar to that of diamond.

i) A major use of silicon carbide is to reinforce aluminium alloys which are used in the construction of spacecraft. Suggest three of its physical properties.

[3]

ii) Describe the bonding in silicon carbide.

Your answer should state which atoms each carbon atom is bonded to, and how many carbon atoms each silicon atom is bonded to.

[2]

Germanium(IV) oxide, GeO₂, has the same giant covalent structure as silicon(IV) oxide. Draw the structural formula of germanium(IV) oxide.

Germanium forms a series of hydrides comparable to the alkanes.

i) Draw the structural formula of the hydride which contains four germanium atoms per molecule.

[1]

ii) Predict the products of the complete combustion of this hydride.

[2]

The properties of five alkenes at room temperature are shown in Table 1.1

Table 1.1

Answer this question using only the information in the table.

Suggest why the densities of the first three alkenes are much lower than the density of pentene and hexene.

The diagrams show part of the structures of five substances, A, B, C, D and E.

Answer the following question about these structures.

Which one of these structures, A, B, C, D or E, is used in cutting tools?

Part of the structure of graphite is shown.

Use the information from the diagram to explain why graphite is used as a lubricant.

The names of eight substances are given.

aluminium oxide calcium oxide ethanol nitrogen

iron(III) oxide methane oxygen silicon(IV) oxide

State which substance has a giant covalent structure.

Carbon is an element which exists in different forms.

Name two forms of the element carbon that have giant covalent structures.

Magnesium is a metal.

Describe the structure and bonding of metals. Include a labelled diagram in your answer.

It was reported from America that a turbine engine, the size of a button, might replace batteries. The engine would be built  from silicon which has suitable properties for this purpose.

The engine will run on a small pack of jet fuel. What other chemical is needed to burn this fuel?

Silicon has the same type of giant covalent structure as diamond.

i) Explain why one atom of either element can form four covalent bonds.

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ii) Predict two physical properties of silicon.

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iii) Name a different element that has a similar structure and properties to silicon.

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Silicon is made by the carbon reduction of the giant covalent compound, silicon(IV) oxide.

i) Balance the equation for the reduction of silicon(IV) oxide.

SiO₂ + C → Si + CO

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ii) Explain why the silicon(IV) oxide is said to be reduced.

[1]

iii) Describe the structure of silicon(IV) oxide. You may use a diagram.

[3]

There are three types of giant structure – ionic, metallic and covalent.

Sodium nitride is an ionic compound. Draw a diagram that shows the formula of the compound, the charges on the ions and the arrangement of the valency electrons around the negative ion.

Use x to represent an electron from a sodium atom.
Use o to represent an electron from a nitrogen atom.

i) Describe metallic bonding.

[3]

ii) Use the above ideas to explain why:

metals are good conductors of electricity,

metals are malleable.

[3]

Silicon(IV) oxide has a giant covalent structure.

i) Describe the structure of silicon(IV) oxide (a diagram is not acceptable).

[3]

ii) Diamond has a similar structure and consequently similar properties. Give two physical properties common to both diamond and silicon(IV) oxide.

[2]

Carbon and silicon are elements in Group IV. Both elements have giant covalent structures.

Diamond and graphite are two forms of the element carbon.

i) Explain why diamond is a very hard substance.

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ii) Give one use of diamond.

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iii) Explain why graphite is a soft material.

[2]

iv) Give one use of graphite.

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Two of the oxides of these elements are carbon dioxide, CO₂, and silicon(IV) oxide, SiO₂.

i) Draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound carbon dioxide.

Use o to represent an electron from a carbon atom. Use x to represent an electron from an oxygen atom.

[3]

ii) A section of the giant covalent structure of silicon(IV) oxide is given below.

Use this diagram to explain why the formula is SiO₂ not SiO₄.

[2]

iii) Predict two differences in the physical properties of these two oxides.

[2]

The first three elements in Group IV are

   Carbon

   Silicon

   Germanium

The element germanium has a diamond-type structure. Describe the structure of germanium. A diagram is acceptable.

Unlike diamond, graphite is soft and is a good conductor of electricity.

i) Explain why graphite has these properties.

[3] 

ii) Give a use of graphite that depends on one of these properties.

Property .................................

Use .................................

[1] 

Carbon dioxide and silicon(IV) oxide have similar formulae but different types of structure.

i) Give the formulae of these oxides.

[1] 

ii) How are their structures different?

[2] 

Silicon(IV) oxide, SiO₂, and zirconium(IV) oxide, ZrO₂, have similar physical properties. Silicon(IV) oxide is acidic and zirconium(IV) oxide is amphoteric.

Silicon(IV) oxide and zirconium(IV) oxide have the same type of structure.

Name this type of structure.

i) Predict three physical properties of these two oxides.

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ii) Name an element which has the same physical properties as these two oxides.

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i) Name a reagent that reacts with the oxides of both elements.

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ii) Name a reagent that reacts with only one of the oxides.

reagent ..........................................

oxide which reacts .........................................

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