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CAMBRIDGE INTERNATIONAL SCHOOL, DUBAI

Subject: Chemistry Year: 10

Name: Acids, Bases & Salts Worksheet-2 Date:

1 The salt magnesium chloride can be prepared by reacting hydrochloric acid with magnesium oxide.

The method for preparing pure dry crystals of magnesium chloride is given.

Complete the missing steps 4 and 6.

1 Add excess magnesium oxide to dilute hydrochloric acid.

2 Warm the mixture to complete the reaction.
3 Filter off the excess magnesium oxide and collect the filtrate.
4 .......................................................................................................................................
5 Remove the crystals.
6 .......................................................................................................................................[2]

[Total: 2]

2 The method for preparing pure dry crystals of zinc chloride is given.

Complete the missing steps 3 and 6.

1 Add excess zinc oxide to dilute hydrochloric acid.

2 Warm the mixture to complete the reaction.
3 .......................................................................................................................................
4 Evaporate the filtrate until the point of crystallisation and leave for crystals to form.
5 Remove the crystals.
6 .......................................................................................................................................[2]

[Total: 2]

3 Describe how to prepare pure dry crystals of sodium sulfate from an aqueous solution of sodium
sulfate.

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[Total: 2]
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4 A student prepares magnesium sulfate crystals, MgSO4, by adding excess magnesium to dilute
sulfuric acid.

Describe two observations which show the reaction has finished.

1 ...............................................................................................................................................

2 ............................................................................................................................................... [2]

[Total: 2]

5 Aqueous potassium hydroxide reacts with a dilute acid to produce aqueous

potassium chloride, KCl(aq), which is a salt.

(a) Name the dilute acid used.

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(b) State the type of reaction taking place.

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(c) Name the experimental technique used when salts are made by reacting a dilute acid with an
aqueous alkali.

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[Total: 3]

6 A student prepares magnesium sulfate crystals, MgSO4, by adding excess magnesium to dilute
sulfuric acid.

The aqueous magnesium sulfate is heated until crystals begin to appear.

(a) Suggest the name for a solution in which no more solute can dissolve.

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(b) Suggest why more crystals of magnesium sulfate appear on cooling.

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[Total: 2]

7 A student prepares calcium nitrate, Ca(NO3)2, by adding calcium carbonate to dilute nitric acid.

The student continues to add calcium carbonate until it is in excess.

The student then removes the excess calcium carbonate by filtration and collects the aqueous
calcium nitrate.

The student gently heats the aqueous calcium nitrate until the solution is saturated.
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(a) Suggest what is meant by the term saturated solution.

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(b) Describe how crystals are produced from a hot saturated solution.

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[Total: 3]

8 A solution is a mixture of a solute and a solvent.

(a) Name the process when a solid substance mixes with a solvent to form a solution.

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(b) Name the type of reaction when two solutions react to form an insoluble substance.

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[Total: 2]
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9 Dilute sulfuric acid and aqueous sodium hydroxide can be used to prepare sodium sulfate crystals
using a method that involves titration.

dilute
sulfuric acid

conical flask

25.0 cm3 aqueous

sodium hydroxide

3 3 3
20.0 cm of dilute sulfuric acid neutralises 25.0 cm of 1.00 mol / dm aqueous sodium hydroxide.

At the end of the titration the conical flask contains aqueous sodium sulfate with the dissolved
indicator as an impurity.

Describe how to prepare a pure sample of sodium sulfate crystals from the original solutions of
dilute sulfuric acid and aqueous sodium hydroxide of the same concentrations.

You are not required to give details of how to carry out the titration.

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[Total: 5]
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10 Some sulfates are hydrated.

When hydrated sodium sulfate crystals, Na2SO4•xH2O, are heated, they give off water.

Na2SO4•xH2O(s) → Na2SO4(s) + xH2O(g)

A student carries out an experiment to determine the value of x in Na2SO4•xH2O.

step 1 Hydrated sodium sulfate crystals are weighed.

step 2 The hydrated sodium sulfate crystals are then heated.

step 3 The remaining solid is weighed.

Describe how the student can check that all the water has been given off.

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[Total: 2]
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11 This question is about salts.

Salts that are insoluble in water are made by precipitation.

• Lead(II) iodide, PbI2, is insoluble in water.

• All nitrates are soluble in water.
• All sodium salts are soluble in water.

You are provided with solid lead(II) nitrate, Pb(NO3)2, and solid sodium iodide, NaI.

Describe how you would make a pure sample of lead(II) iodide by precipitation.

Your answer should include:

• practical details
• a chemical equation for the precipitation reaction.

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[Total: 5]
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12 This question is about salts.

Salts that are soluble in water can be made by the reaction between insoluble carbonates and
dilute acids. Zinc sulfate is soluble in water.

You are provided with solid zinc carbonate, ZnCO3, and dilute sulfuric acid, H2SO4.

Describe how you would make a pure sample of zinc sulfate crystals.

Your answer should include:

• practical details
• how you would make sure that all the dilute sulfuric acid has reacted
• a chemical equation for the reaction.

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[Total: 5]

13 Insoluble salts can be made by mixing solutions of two soluble salts.

A student followed the procedure shown to make silver bromide, an insoluble salt.

step 1 Add aqueous silver nitrate to a beaker. Then add aqueous potassium bromide and stir.

step 2 Filter the mixture formed in step 1.

step 3 Dry the residue

(a) State the term used to describe this method of making salts.

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(b) Give the observation the student would make during step 1.

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(c) Write the ionic equation for the reaction between aqueous silver nitrate and aqueous potassium
bromide

Include state symbols.

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[Total: 5]

14 Describe how you could prepare a pure sample of crystals of hydrated zinc sulfate using dilute
sulfuric acid and an excess of zinc.

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[Total: 3]

15 Describe how you could prepare a pure sample of crystals of hydrated copper(II) sulfate using
dilute sulfuric acid and an excess of copper(II) oxide.

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[Total: 3]

16 A student prepares crystals of magnesium chloride by adding an excess of magnesium carbonate

3 3
to 50.00 cm of 2.00 mol / dm hydrochloric acid.

The student filters the mixture and rinses the residue.

(a) Why does the student add an excess of magnesium carbonate?

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(b) Why does the student rinse the residue?

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(c) Describe how the student would obtain pure crystals of magnesium chloride from the filtrate.

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[Total: 5]

17 Ethanoic acid, CH3COOH, is a weak acid. It reacts with copper(II) carbonate to form the salt
copper(II) ethanoate, Cu(CH3COO)2.

Describe how a crystalline sample of copper(II) ethanoate can be prepared starting with
ethanoic acid and copper(II) carbonate.

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[Total: 3]

18 All sodium salts are soluble in water. All nitrates are soluble in water. Barium carbonate is insoluble
in water.

Describe how you would make a pure, dry sample of barium carbonate by precipitation.
Include:
● the names of the starting materials
● full practical details
● a chemical equation.

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[Total: 5]