Properties of ionic compounds

This question is about metals and metal compounds.

The method used to extract a metal depends on the reactivity of the metal.

Explain which method is used to extract sodium metal from sodium chloride.

The diagram shows the arrangement of particles in a pure metal.

Explain why pure metals are soft.

The diagram shows the electronic structure of an atom of sodium and an atom of oxygen.

Describe, in terms of electrons, what happens when sodium reacts with oxygen.

The table shows the melting points of sodium and sodium oxide.

Explain why sodium and sodium oxide have different melting points.

In your answer you should refer to:

• the structures of sodium and sodium oxide

• the forces between the particles

This question is about the reactions of some compounds of lead.

Lead can be extracted from lead(II) sulfide, PbS, in two stages.

Stage 1 lead(II) sulfide is heated in air and reacts with oxygen to produce lead(II) oxide, PbO, and sulfur dioxide

Stage 2 lead(II) oxide is heated with carbon in a furnace

Write a chemical equation for the reaction in stage 1.

Give a reason why sulfur dioxide should not be released into the atmosphere.

This is the equation for stage 2.

A mass of 892 tonnes of lead(II) oxide is heated in a furnace with an excess of carbon.

Calculate the maximum mass, in tonnes, of carbon dioxide that could be released into the atmosphere.

[1 tonne = 110⁶g]

[for PbO, M_r = 223 for CO₂, M_r = 44]

The diagram shows the structures of lead(II) sulfide and sulfur dioxide.

Explain, in terms of bonding and structure, why lead(II) sulfide is a solid with a very high melting point at room temperature and why sulfur dioxide is a gas at room temperature.

lead(II) sulfide

sulfur dioxide

A different oxide of lead contains 90.7% by mass of lead and 9.3% by mass of oxygen.

Determine the empirical formula of this oxide of lead.

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.

A scientist reacts lead(II) nitrate solution with sodium bromide solution.

This is the equation for the reaction.

Pb(NO₃)₂(aq) + 2NaBr(aq) PbBr₂(s) + 2NaNO₃(aq)

Describe how the scientist could obtain a pure dry sample of lead(II) bromide (PbBr₂) from the reaction mixture.

The scientist reacts an excess of lead(II) nitrate solution with 25 cm³ of sodium bromide solution of concentration 2.0 mol/dm³.

Show that the amount of sodium bromide used is 0.050 mol.

Show that the maximum theoretical mass of lead(II) bromide is approximately 9 g.

[for PbBr₂ M_r = 367]

The scientist electrolyses molten lead(II) bromide using this apparatus.

Explain why lead(II) bromide needs to be molten rather than solid for electrolysis to occur.

The electrolyte is at a temperature of 400C.

Explain a suitable material for the electrodes.

Give the half‑equation that occurs at the negative electrode.

Bromine forms at the positive electrode.

This is the half‑equation for the reaction at the positive electrode.

State what is observed at the positive electrode.

State why the half‑equation represents an oxidation reaction.

This question is about ionic compounds.

Calcium nitrate has the formula Ca(NO₃)₂

Give the formula of each ion in calcium nitrate.

calcium ion

nitrate ion

Explain why calcium nitrate has a high melting point.

Refer to structure and bonding in your answer.

Calcium nitrate decomposes when heated.

Complete the chemical equation for the decomposition of calcium nitrate.

A student has four unlabelled beakers, each containing a colourless solution of a different salt.

These are the four salt solutions.

• calcium bromide

• calcium chloride

• sodium chloride

• sodium sulfate

Describe a series of tests to identify each solution.

Do not refer to safety precautions in your answer.

This question is about the insoluble salt, lead(II) bromide.

Lead(II) bromide can be made by a precipitation reaction.

This is the equation for the reaction.

Pb(NO₃)₂(aq) + 2KBr(aq) PbBr₂(s) + 2KNO₃(aq)

Describe how solutions of lead nitrate and potassium bromide can be used to make a pure, dry sample of lead(II) bromide.

A solution containing 0.150 mol of lead(II) nitrate is reacted with an excess of potassium bromide solution.

A mass of 49.6 g of pure, dry lead(II) bromide is produced.

Show, by calculation, that the percentage yield of lead(II) bromide is 90.1%.

[for PbBr₂, M_r = 367]

A student investigates the change in electrical conductivity as dilute lead(II) nitrate solution is added to dilute potassium bromide solution.

This is the student’s method.

Step 1add 50 cm³ of potassium bromide solution to a beaker

Step 2 measure the electrical conductivity of the solution

Step 3add 10 cm³ of lead(II) nitrate solution to the beaker

Step 4 stir the mixture

Step 5 measure the electrical conductivity of the mixture

Repeat steps 3, 4 and 5 until a total of 50 cm³ of lead(II) nitrate solution has been added.

The table shows the student’s results.

Plot the student’s results on the grid.

Draw a line of best fit, ignoring the anomalous result.

Total volume of lead(II) nitrate in cm³

Explain the shape of the graph.

Suggest a mistake the student could have made to cause the anomalous result.

Further 10 cm³ volumes of lead(II) nitrate are added to the beaker so the lead(II) nitrate is in excess.

Predict what will happen to the conductivity of the mixture when the lead(II) nitrate is in excess.

The diagram shows the electrolysis of molten lead(II) bromide, PbBr₂

This is the ionic half‑equation for the formation of bromine at electrode A.

Give a reason why this half‑equation shows oxidation.

This question is about ionic compounds.

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

Complete the table by giving the missing formulae.

Give the name of the compound with the formula MgO

Calculate the relative formula mass (M_r) of Na₃N

[for Na, A_r = 23 for N, A_r = 14]

The diagram shows the arrangement of electrons in atoms of lithium and in an atom of oxygen.

Describe the changes in the electron configurations of lithium and oxygen when these atoms form lithium oxide, Li₂O

Lithium oxide has a giant ionic structure.

Explain why lithium oxide has a high melting point.

This question is about metals.

Explain why metals are malleable.

Explain why molten sodium chloride conducts electricity.

Explain how sodium metal forms at the negative electrode.

Write an ionic half-equation for the formation of chlorine gas at the positive electrode.

Give a reason why sodium metal does not form in the electrolysis of an aqueous solution of sodium chloride.

Copper can be produced by reacting an oxide of copper with methane.

The diagram shows the apparatus used.

The oxide of copper is heated until the reaction is complete.

The table shows the results.

Use the results to show that this oxide has the empirical formula CuO

[for Cu, A_r = 63.5 for O, A_r = 16]

This question is about the element phosphorus and some of its compounds.

The atomic number of phosphorus is 15

Give the electronic configuration of an atom of phosphorus.

Calcium phosphide is an ionic compound used in pest control.

The formula of a calcium ion is Ca²⁺

Explain why the formula of calcium phosphide is Ca₃P₂

Calcium phosphide can be produced by heating calcium phosphate with carbon.

Complete the equation for the reaction.

Explain the role of carbon in the reaction.

Calcium phosphide reacts with water to form calcium hydroxide and phosphine, PH₃

Give a chemical equation for this reaction.

Explain why calcium phosphide has a high melting point.

You should refer to structure and bonding in your answer.

Iron metal was discovered several thousand years ago. Iron is produced industrially from iron(III) oxide by extraction using carbon.

Sodium is a metal in Group 1 of the Periodic Table. Sodium was discovered by Sir Humphrey Davy in 1807. It is produced industrially by the electrolysis of sodium chloride.

Explain, using the reactivity series, why carbon can be used to extract iron from iron(III) oxide.

Suggest why sodium was not discovered until 1807.

The diagram shows a simplified version of the Downs cell, which can be used to produce sodium industrially. The electrolyte is molten sodium chloride.

Explain why the molten electrolyte conducts electricity.

What is the formula of the cation in the electrolyte?

During the production of sodium, small explosions can be heard.

Explain why using sodium chloride that is not completely dry could cause these small explosions.

Give ionic half-equations for the reactions at the anode and cathode.

Explain why the reactivity of metals in Group 1 increases from lithium to potassium.

A student investigates how the electrical conductivity changes as dilute sulfuric acid is added to barium hydroxide solution.

This is the student’s method.

Step 1 =$~dd=RMKM cm³ of barium hydroxide solution to a beaker

Step 2 measure the electrical conductivity of the solution

Step 3 =$~dd=NMKM cm³ of dilute sulfuric acid to the beaker

Step 4 stir the mixture

Step 5 measure the electrical conductivity of the mixture

Step 6 repeat steps 3 to 5 until a total of 100 cm3³ of dilute sulfuric acid has been added

The table shows the student’s results.

Name a piece of apparatus the student could use to add 10.0 cm³ of dilute sulfuric acid to the beaker.

Plot the student’s results.

Ignoring the anomalous result, draw two lines of best fit, making sure that the two lines cross.

Total volume of acid added in cm³

Give the trend shown on the graph for the first 50 cm³ of acid added.

Suggest a mistake the student could have made to cause the anomalous result.

This is the equation for the reaction.

When 50 cm³ of dilute sulfuric acid have been added, only barium sulfate and water are present in the mixture.

Explain why this mixture does not conduct electricity. Refer to the type of bonding in barium sulfate and in water in your answer.

Name a technique the student could use to separate barium sulfate from the mixture after 100 cm³ of dilute sulfuric acid has been added.

This question is about sodium oxide, Na₂O

The diagram shows the electronic configuration of atoms of sodium and oxygen.

Describe the changes in the electronic configuration of the atoms of sodium and oxygen to form the ions in sodium oxide.

Calculate the relative formula mass (M_r) of sodium oxide, Na₂O, using information from the Periodic Table.

Explain why solid sodium oxide does not conduct electricity.

Give a test to show that sodium oxide contains sodium ions.

When sodium oxide is heated it reacts to form sodium metal and sodium peroxide, Na₂O₂

Complete the equation for this reaction.

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 arrangement of electrons in an atom of calcium and in an atom of chlorine.

Describe, in terms of electrons, what happens when calcium reacts with chlorine to form the ionic compound calcium chloride, CaCl₂

Describe tests to show that an aqueous solution of calcium chloride contains calcium ions and chloride ions.

Solid calcium chloride does not conduct electricity. Aqueous solutions of calcium chloride do conduct electricity.

A student uses this method to investigate how the conductivity of a solution changes when calcium chloride is dissolved in pure water.

Step 1 add 100 cm³ of pure water to a beaker

Step 2 add one spatula of solid calcium chloride to the beaker

Step 3 stir the solution

Step 4 measure the conductivity of the solution

Step 5 repeat until nine spatulas of solid calcium chloride have been added

The table shows the student’s results.

Plot the results on the grid and draw two straight lines of best fit.

Ignore the anomalous result.

State the trend shown on the graph for the first six spatulas of calcium chloride.

Suggest an error the student could have made to cause the anomalous result.

Describe another way to make solid calcium chloride conduct electricity.

This question is about the metal, lead.

Explain why metals, such as lead, are malleable.

A teacher uses this apparatus in a fume cupboard to demonstrate the electrolysis of lead(II) bromide.

The lead(II) bromide is heated until it melts.

When the lead(II) bromide melts, the lamp lights.

One of the products of this electrolysis is lead.

State why solid lead(II) bromide does not conduct electricity.

Bromine is formed by the oxidation of bromide ions at the positive electrode.

Complete the ionic half-equation for the oxidation of bromide ions.

Explain why lead metal forms at the negative electrode.

The teacher stops heating the mixture and allows it to solidify.

Suggest why the lamp stays alight.

This question is about the halogens and their compounds.

The table gives the colour and physical state at room temperature of the halogens.

Complete the table by predicting the colour of astatine and the physical state of fluorine at room temperature.

Chlorine gas is bubbled into a colourless solution of potassium bromide.

Explain why the solution turns orange.

Potassium bromide is an ionic compound.

Draw diagrams to show the outer electrons in a potassium ion and in a bromide ion.

Include the charges on the ions.

A student sets up a circuit to test the electrical conductivity of water, solid sodium chloride and aqueous sodium chloride.

The table shows the student’s results.

Explain these results, with reference to the structure and bonding of the substances.

A concentrated aqueous solution of sodium chloride is electrolysed using graphite electrodes.

Chlorine is formed at the positive electrode (anode).

Give an ionic half‑equation for the formation of chlorine at the positive electrode.

State why this ionic half‑equation represents an oxidation reaction.

Which substance is formed at the negative electrode (cathode)?