Covalent bonding

This question is about organic compounds.

Chloroethene (C₂H₃Cl) is a covalent molecule that is used to make poly(chloroethene).

This is the displayed formula of chloroethene.

Draw a dot‑and‑cross diagram of chloroethene.

Show only the outer shell electrons.

Describe, in terms of electrostatic attraction, what is meant by a covalent bond.

Chloroethene is a monomer.

Draw the displayed formula of the repeat unit of poly(chloroethene).

Poly(chloroethene) is non‑biodegradable.

There are two main methods used to dispose of poly(chloroethene).

Describe one problem caused by each method.

An organic compound contains this percentage composition by mass.

C = 22.0% H = 4.6% Br = 73.4%

Calculate the empirical formula of this compound.

Ethane and ethene undergo different types of reaction with bromine.

Describe the differences between these two reactions.

This question is about ionic and covalent compounds.

The table gives the formulae of some positive ions, some negative ions and some compounds containing these ions.

Complete the table by giving the three missing formulae.

Give the name of the compound with the formula Al₂(SO₄)₃

The diagram shows the arrangement of electrons in an atom of magnesium and an atom of chlorine.

Describe, in terms of electrons, what happens when magnesium atoms and chlorine atoms form magnesium chloride.

Complete the dot-and-cross diagram to show the outer shell electrons in a molecule of ammonia.

Describe the forces of attraction in a covalent bond.

The table shows the formulae of some positive and negative ions, and the formulae of some compounds containing these ions.

Complete the table by giving the formulae of the missing compounds.

Give the name of the compound with the formula ZnSO₄

Hydrogen chloride and magnesium chloride have different types of bonding and have different structures.

Complete the dot-and-cross diagram to show the outer shell electrons in a molecule of hydrogen chloride.

H C l

The diagram shows the electronic configuration of a magnesium atom and of a chlorine atom.

Draw the electronic configuration of a magnesium ion and of a chloride ion in the boxes.

Show the charge on each ion.

Explain why magnesium chloride has a much higher melting point than hydrogen chloride.

Refer to structure and bonding in your answer.

Diamond and graphite are both forms of the element carbon.

Diamond and graphite both have covalent bonds and giant covalent structures.

The diagram represents the structure of diamond and the structure of graphite.

Give a reason why diamond is an element.

Describe the forces of attraction in a covalent bond.

Explain why graphite conducts electricity.

Explain why diamond is hard but graphite is soft.

Another form of carbon has molecules with the formula C_x

x represents the number of carbon atoms in each molecule.

Each molecule of C_x has a mass of 1.40 × 10⁻²¹ g.

One mole of C_x contains 6.02 × 10²³ molecules.

Calculate the M_r of C_x and the value of x

[for carbon, A_r = 12]

This question is about hydrogen chloride (HC l).

Hydrogen chloride is a covalent compound.

State, in terms of electrostatic attraction, what is meant by a covalent bond.

When hydrogen chloride gas is dissolved in an organic solvent, the hydrogen chloride remains a covalent molecule.

When hydrogen chloride gas is dissolved in water, ions are formed.

Explain what happens when dry blue litmus paper is dipped into separate samples of each solution.

In the presence of ultraviolet radiation, hydrogen reacts with chlorine to form hydrogen chloride.

This is the equation for the reaction.

The table shows the bond energies.

Calculate the enthalpy change (Δ H), in kJ/mol, for the reaction.

Include a sign in your answer.

ΔH =_........ kJ/mol

Draw a reaction profile for the reaction.

Label the reactants, the products, ΔH and the activation energy (E_a).

A student uses this apparatus to investigate the decomposition of hydrogen peroxide solution.

This is the equation for the reaction.

Give the test for oxygen.

Complete the dot‑and‑cross diagram for a molecule of hydrogen peroxide.

Show outer electrons only.

H O O H

The student measures the volume of oxygen collected at regular intervals until the reaction stops.

The table shows the student’s results.

Plot the student’s results on the grid.

Draw a curve of best fit.

Explain in terms of particle collision theory how decreasing the concentration affects the rate of a reaction.

The student repeats the experiment using the same volume of hydrogen peroxide solution but with half the original concentration.

All other conditions are kept the same.

On the grid, draw the curve you would expect the student to obtain.

In this reaction, the manganese(IV) oxide acts as a catalyst.

Explain how a catalyst works.

Diamond and graphite are made of carbon atoms, joined together by covalent bonds.

The diagram shows their structures.

State, in terms of electrostatic attractions, what is meant by a covalent bond.

Explain why diamond has a high melting point.

Explain why graphite is a good conductor of electricity.

C₆₀ fullerene is a molecule made of 60 carbon atoms.

The diagram shows the structure of C₆₀ fullerene.

One mole of atoms contains 6.010²³ atoms.

Determine the number of atoms in one mole of C₆₀ fullerene.

Give your answer in standard form.

This question is about unsaturated hydrocarbons.

Ethene (C₂H₄) is a member of the homologous series of alkenes.

Give two characteristics of a homologous series.

Draw a dot-and-cross diagram to show the bonding in a molecule of ethene.

Show outer electrons only.

Propene (C₃H₆) is another member of the homologous series of alkenes.

State why the empirical formula of all alkenes in this homologous series is CH₂

Propene can be polymerised to form poly(propene).

Draw the displayed formula of propene and the repeat unit of poly(propene).

propene
repeat unit of poly(propene)

This is the structural formula of another hydrocarbon compound.

Give the molecular formula and the empirical formula of this compound.

molecular formula

empirical formula

Explain why this compound is an unsaturated hydrocarbon.

Describe a test to show that this hydrocarbon is unsaturated.

This question is about propene.

The structural formula of propene is CH₃CH CH₂

Complete the dot-and-cross diagram for a molecule of propene.

Describe the forces of attraction that hold the atoms together in a molecule of propene.

The alkane pentadecane has the formula C₁₅H₃₂

Describe how propene can be produced from pentadecane.

Propene is used to make poly(propene).

Complete the equation for the formation of poly(propene).

Explain why the disposal of poly(propene) in landfill sites is a problem.

Propene can be converted into compound X.

Compound X contains these percentages by mass.

• carbon 60%

• hydrogen 13.3%

• oxygen 26.7%

Compound X has an M_r of 60

Determine the molecular formula of compound X.

Propene and compound X both have simple molecular structures.

Explain why compound X has a higher boiling point than propene.

This question is about organic compounds.

Give the total number of atoms in one molecule of methanoic acid.

Determine the relative molecular mass (M_r) of methanoic acid.

Explain why methanoic acid is not a hydrocarbon.

The atoms in methanoic acid are held together by covalent bonds.

State, in terms of electrostatic attractions, what is meant by the term covalent bond.

Draw a dot‑and‑cross diagram to show the bonding in a molecule of methanoic acid.

Show only the outer electrons of each atom.

Calculate the empirical formula of the organic compound with this composition by mass.

C = 52.2% H = 13.0% O = 34.8%

This question is about substances that contain covalent bonds.

The diagram represents a molecule of oxygen.

Describe the forces of attraction in a covalent bond.

The table shows the boiling points of three Group 7 elements.

Explain the trend in the boiling points.

Graphite is a naturally-occurring form of carbon.

Explain why graphite is soft and conducts electricity.

Refer to structure and bonding in your answer.

This question is about hydrazine, N₂H₄

This is the displayed formula for a molecule of hydrazine.

Complete the dot‑and‑cross diagram for hydrazine.

Use the data in the table to calculate the total energy needed to break all the bonds in the reactants.

Use the data in the table to calculate the total energy released when all the bonds in the products are made.

Calculate the enthalpy change, Δ H, in kJ/mol, for the reaction.

ΔH =_........ kJ/mol

Explain, in terms of bonds broken and bonds made, why this reaction is exothermic.

A sample of hydrazine is completely decomposed.

This is the equation for the decomposition of hydrazine.

The products of the decomposition are bubbled through 1100 cm³ of water.

The ammonia completely dissolves in the water, but nitrogen is insoluble in water.

The nitrogen has a volume of 1570 cm³ at room temperature and pressure (rtp).

Calculate the concentration, in mol/dm³, of the ammonia solution.

Give your answer to 3 significant figures.

[for a gas at rtp, molar volume = 24 000 cm³]

concentration =_........ mol/dm

Silicon hydride (SiH₄) and silicon dioxide (SiO₂) both contain covalent bonds but they have different structures.

Describe the forces of attraction in a covalent bond.

Complete the diagram to show the outer shell electrons in a molecule of silicon hydride (SiH₄).

The diagram represents part of the structure of silicon dioxide (SiO₂).

State how the diagram shows that the atom labelled A is oxygen, not silicon.

Silicon hydride has a simple molecular structure.

Silicon dioxide has the same type of structure as diamond.

Explain why silicon dioxide has a much higher melting point than silicon hydride.

Refer to structure and bonding in your answer.

Silicon hydride reacts with oxygen to form silicon dioxide and water.

Write a chemical equation for the reaction between silicon hydride and oxygen.

This question is about ammonia and ammonium compounds.

Ammonia (NH₃) is a simple covalent molecule.

Draw a dot-and-cross diagram to show the bonding in a molecule of ammonia.

The table shows the names and formulae of some ammonium compounds.

Complete the table by giving the missing information.

When ammonia reacts with sulfuric acid, ammonium sulfate is formed.

Write a chemical equation for this reaction.

Describe a test for ammonium ions.

The table gives some information about ammonia and ammonium compounds.

Calculate the percentage of nitrogen in ammonium nitrate.

[M_r of NH₄NO₃ = 80]

Fertilisers add nitrogen to the soil to help plants grow.

Ammonia and ammonium sulfate can both be used as fertilisers.

Discuss the advantages and disadvantages of using each of these compounds as fertilisers.

Use information from the table in your answer.

[pH of rainwater is approximately 5.6]

This question is about substances with covalent bonds.

Draw a dot and cross diagram to show the outer shell electrons in a molecule

Describe the forces of attraction in a covalent bond.

The diagram shows three different structures of carbon.

Name structure A.

Graphite and C₆₀ fullerene contain covalent bonds, but have different structures.

Explain why C₆₀ fullerene has a much lower melting point than graphite.

Refer to structure and bonding in your answer.

The formation of ions and covalent bonds involves electrons.

The table gives the electronic configurations of atoms of hydrogen, lithium and chlorine.

Describe the different roles of electrons in the formation of

ions in lithium chloride

covalent bonds in hydrogen chloride

Explain why lithium chloride has a higher melting point than hydrogen chloride.

Refer to structure and bonding in your answer.

The diagram shows the displayed formula of the organic compound methanol, CH₃OH

Determine the number of atoms in one molecule of methanol.

State why methanol is not a hydrocarbon.

The atoms in methanol are held together by covalent bonds.

State what is meant by the term covalent bond.

Draw a dot-and-cross diagram to show the bonding in a molecule of methanol.

Show only the outer electrons of each atom.

Another organic compound has the percentage composition by mass

C = 38.7% H = 9.7% O = 51.6%

Calculate the empirical formula of this compound.

The relative molecular mass (M_r) of the compound is 62

Determine the molecular formula of the compound.

Chlorine, bromine and iodine are elements in the Periodic Table.

Explain how the position of these elements in the Periodic Table depends on their electronic configurations.

Chlorine reacts with methane to form CH₃Cl and HCl

State the condition necessary for this reaction.

Give the equation for this reaction.

The bonds in a molecule of CH₃Cl are covalent.

Explain, in terms of electrostatic attractions, what is meant by a covalent bond.

CH₃Cl has a simple molecular structure.

Explain why CH₃Cl has a low boiling point.

Graphite is another substance that contains covalent bonds.

The diagram shows the structure of graphite.

Most covalent substances do not conduct electricity.

Explain why graphite is able to conduct electricity.

This question is about carbon and its compounds.

Draw a dot-and-cross diagram to show the outer shell electrons in a molecule

The atoms in carbon dioxide are held together by covalent bonds.

Describe the forces of attraction in a covalent bond.

The diagram shows three different structures of carbon.

Explain why graphite conducts electricity.

Explain why diamond has a much higher melting point than C₆₀ fullerene.

Refer to structure and bonding in your answer.