GCSEChemistry: Combined ScienceEdexcelExam Questions3. Chemical changes3.1 Acids

Acids (Edexcel GCSE Chemistry: Combined Science)

Exam Questions

2 hours25 questions
Easy
Medium
Hard
1a1 mark
a)
When solid sodium chloride is mixed with water, sodium chloride solution forms.

What name is given to the process of mixing a solid with water to form a solution?
(1)
  ☐ A crystallising
  ☐ B diluting 
  ☐ C dissolving 
  ☐ D melting 

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1b4 marks
b)
Sodium reacts with hydrochloric acid to form sodium chloride and hydrogen.

i)
Write the word equation for this reaction.
(2)

.............................................................. → ...............................................................

ii)
The hazard symbol shown in Figure 1 is used on containers of sodium.

fig-1-q1aii-1cho-1f-paper-1-nov-2020

Figure 1

What is the meaning of this hazard symbol?

(1)

  ☐ A corrosive
  ☐ B flammable 
  ☐ C oxidising 
  ☐ D toxic 

iii)
Hydrogen has one electron in its electron shell.
Figure 2 shows the incomplete dot and cross diagram of a hydrogen molecule.

Complete Figure 2 to show the electrons in the covalent bond between the two atoms of hydrogen.

(1)

fig-2-q1biii-1cho-1f-paper-1-nov-2020

Figure 2

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1c2 marks
c)
The pH of a sodium chloride solution was measured.

i)
State what could be used to measure the pH of a solution.
(1)
ii)
Sodium chloride solution is neutral.

Give the pH of this solution.
(1)

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25 marks
The fertiliser ammonium sulfate may be made by titrating ammonia solution with dilute sulfuric acid.

Three pieces of apparatus, P, Q and R, used to measure volumes of liquid are shown in Figure 1.
fig-1-q1b-1cho-1f-paper-1-nov-2021

Figure 1

i)
Give the names of the pieces of apparatus P and Q.

(2)
P...............................................
Q ...............................................

ii)

In the titration experiment, small volumes of dilute sulfuric acid are added gradually to the ammonia solution in a flask.

Give the letter, P, Q or R, of the piece of apparatus in Figure 1 that should be used to add the dilute sulfuric acid.

(1)

iii)
The titration experiment is used to produce a solution of ammonium sulfate.

Describe how solid ammonium sulfate should be obtained from this solution.

(2)

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1a1 mark

Ammonium phosphate and ammonium sulfate are made from ammonia.

These compounds can be used as fertilisers.

a)
Ammonia solution is alkaline.
Which of the following could be used to show that ammonia solution is alkaline?

(1)

  ☐ A conical flask
  ☐ B pH meter
  ☐ C pipette
  ☐ D thermometer

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1b1 mark

Ammonium phosphate and ammonium sulfate are made from ammonia.

These compounds can be used as fertilisers.

b)
Give one advantage of using fertilisers made from ammonia rather than using manure.
(1)

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1c4 marks
c)
The fertiliser ammonium phosphate was made by reacting ammonia solution with dilute phosphoric acid.

i)
In the first step, 25 cm3 of dilute phosphoric acid was placed in a beaker.

Give the name of a piece of apparatus that could be used to measure out the 25 cm3 dilute phosphoric acid.

(1)

ii)
Complete the word equation for this reaction.

   ammonia + ................................... → .....................................

(1)

iii)
Some ammonium phosphate solution was made.

Describe how pure, dry crystals of ammonium phosphate are obtained from the ammonium phosphate solution.

(2)

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1d1 mark
d)
The formula of ammonium sulfate is (NH4)2SO4
What is the empirical formula of ammonium sulfate?
(1)

  ☐ A NHSO
  ☐ B NH2SO2
  ☐ C NH4SO4
  ☐ D N2H8SO4

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21 mark

A student added some sulfuric acid gradually to a solution of ammonia until it was in excess.

What happens to the pH during this reaction?

(1)

  ☐ A pH of ammonia at start: 11 pH after excess sulfuric acid: 7
  ☐ B pH of ammonia at start: 7 pH after excess sulfuric acid: 13
  ☐ C pH of ammonia at start: 11 pH after excess sulfuric acid: 2
  ☐ D pH of ammonia at start: 3 pH after excess sulfuric acid: 8

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31 mark

What is the ionic equation for neutralisation?

(1)

  ☐ A 2H+ (aq) + OH- (aq)   →    H2O (l)
  ☐ B H+ (aq) + OH- (aq)   →    H2O (aq)
  ☐ C H+ (aq) + OH- (aq)   →    H2O (l)
  ☐ D 2H2 + O2    →       2H2O

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4a2 marks

The method used to prepare a salt depends on its solubility in water.

a)
Complete Figure 19 by placing one tick in each row to show whether the salt is soluble or insoluble.

salt soluble insoluble
ammonium chloride    
lithium sulfate    
magnesium carbonate    

Figure 19

(2)

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4b4 marks
b)

The method used to make the lead sulfate is:

  • pour 100 cm3 lead nitrate solution into a beaker
  • add drops of sodium sulfate solution until a precipitate is seen
  • allow the precipitate to settle to the bottom of the beaker
  • pour off the liquid
  • use a spatula to transfer the solid lead sulfate onto a filter paper.

Explain two ways of improving this experimental method in order to increase the amount and quality of lead sulfate that could be obtained from 100 cm3 of lead nitrate solution.

(4)

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51 mark

Calcium reacts with hydrochloric acid to form the salt, calcium chloride and another product. 

calcium  +   hydrochloric acid            →         calcium chloride  + ___________

What is the unknown product?

(1)

  ☐ A Water
  ☐ B Oxygen
  ☐ C Hydrogen
  ☐ D Carbon dioxide

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61 mark

Which statement correctly describes a strong acid? 

(1)

  ☐ A Fully ionise in solution and have a high concentration of H+ ions
  ☐ B Fully ionise in solution and have a low concentration of H+ ions
  ☐ C Partially ionise in solution and have a high concentration of H+ ions
  ☐ D Partially ionise in solution and have a low concentration of H+ ions

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7a2 marks

Higher Only

Some acids such as hydrochloric acid are described as strong acids.
Some acids such as ethanoic acid are described as weak acids.

a)

 
i)
Explain the difference between a strong acid and a weak acid.

(2)

ii)

Give a reason why adding hydroxide ions to an acid solution leads to an increase in pH.

(1)

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7b2 marks
b)
The salt zinc nitrate can be made by reacting zinc oxide, ZnO, with dilute nitric acid, HNO3.

   Write the balanced equation for this reaction.

(2)

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7c
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c)
50 cm3 of potassium hydroxide solution of concentration 40g dm–3 is needed for an experiment.

Calculate the mass of potassium hydroxide that must be dissolved in water to make 50 cm3 of solution of this concentration.

(2)

mass of potassium hydroxide = ..................................................................... g

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7d6 marks
d)
Salts of metals can be made by reacting one of the metal’s compounds with the appropriate acid.

Plan an experiment to prepare pure, dry crystals of magnesium sulfate, MgSO4 , by reacting a suitable magnesium compound with a suitable acid.

You may use equations if you wish.

(6)

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81 mark

A student making copper sulfate crystals used the method below. 

RWJ7i1xw_4-2-making-copper-sulfate

Unreacted copper carbonate was left over as it had been added in excess.

What is the reason for adding it in excess and what would step 3 be of this method?

(1)

      Reason Step 3
  ☐ A to produce a greater amount of salt crystals filtration
  ☐ B to improve the colour intensity of the crystals crystallisation
  ☐ C to ensure all the acid reacts filtration
  ☐ D to increase the rate of reaction evaporation

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9a2 marks
a)
State two characteristic properties of metals.
(2)
property 1 ....................................................................

property 2 ....................................................................

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9b1 mark
b)
Acids are used to make salts.

Give the name of the acid used to make chlorides.
(1)

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9c4 marks
c)
Salts of metals can be prepared by reacting the metal with an acid to produce the salt and hydrogen.

i)
Describe the test to show that the gas is hydrogen.
(2)
ii)
Nickel is a metal.
Explain how the structure of a nickel atom, Ni, changes when it forms a nickel ion, Ni2+.
(2)

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9d2 marks
d)
A nickel sulfate solution is made by dissolving 23.5 g of nickel sulfate to make 250 cm3 of solution.
(2)
concentration = ...................................................... g dm-3

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9e3 marks
e)
Excess solid nickel carbonate is added to dilute sulfuric acid in a beaker.

nickel carbonate + sulfuric acid → nickel sulfate + carbon dioxide + water

Nickel sulfate is formed in solution.
Describe how a sample of pure, dry nickel sulfate crystals can be obtained from the mixture of nickel sulfate solution and excess solid nickel carbonate in the beaker.
(3)

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101 mark

Which is the correct method for testing for hydrogen gas?

(1)

  ☐ A Hold the tube containing the gas upright and place a lit splint at the end of the tube
  ☐ B Hold the tube containing the gas upright and place a glowing splint at the end of the tube
  ☐ C Hold the tube containing the gas angled down and place a lit splint at the end of the tube
  ☐ D Hold the tube containing the gas angled down and place a glowing splint at the end of the tube

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111 mark

Which is not true about the test for carbon dioxide gas?

(1)

  ☐ A The gas is bubbled through limewater solution
  ☐ B Limewater is calcium hydroxide solution
  ☐ C The solution will turn cloudy due to the formation of a white precipitate
  ☐ D The colour will fade after a few minutes

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12a
Sme Calculator5 marks

The word equation for the reaction between copper carbonate and dilute sulfuric acid is

copper space carbonate space plus space sulfuric space acid space rightwards arrow space copper space sulfate space plus space carbon space dioxide space plus water

a)
i)
Complete the balanced equation for this reaction.

CuCO3 + ............................... → ............................... + CO2 + H2O
(2)
ii)
Calculate the relative formula mass of copper carbonate, CuCO3.
(relative atomic masses: C = 12.0, O = 16.0, Cu = 63.5)
(2)
relative formula mass of CuCO3 = ...........................

iii)
What is the chemical test to show that a gas is carbon dioxide?
(1)

  ☐ A bubble the gas through limewater, limewater turns cloudy
  ☐ B put damp blue litmus paper in the gas, litmus paper turns red 
  ☐ C put a lighted splint into the gas, splint is extinguished 
  ☐ D measure the pH of the gas, pH = 4 

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12b8 marks
b)
Figure 12 shows a conical flask containing dilute sulfuric acid.
Copper carbonate is added to the acid in the flask.
The copper carbonate is added one spatula measure at a time until the reaction has finished.

fig-12-q9b-1cho-1f-paper-1-nov-2020

Figure 12

i)
State two observations that would show the reaction has finished.
(2)
ii)
Describe how you would obtain a solution of copper sulfate from the mixture and how you would obtain pure, dry copper sulfate crystals from this solution.
Your description should include the apparatus you would use.
You may wish to use diagrams in your answer.
(6)

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12c2 marks
c)
The electronic configuration of carbon is 2.4
The electronic configuration of oxygen is 2.6

Draw a dot and cross diagram for a molecule of carbon dioxide.

Show outer electrons only.
(2)

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131 mark

Indicators are used during a titration to observe the end point. 

Different indicators turn different colours in acids and alkalis.

Indicator Colour in acid  Colour in alkali 
methyl orange red  yellow
universal indicator red  orange
litmus red  purple
phenolphthalein red  colourless 

Which indicator displays the correct colour in each solution?

(1)

  ☐ A Methyl orange
  ☐ B Universal indicator
  ☐ C Litmus
  ☐ D Phenolphthalein

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14a5 marks
a)

Hydrochloric acid reacts with solid B.
Solid B is an alkali.

A student carries out an experiment to see how the pH changes when different masses of solid B are added to dilute hydrochloric acid.

The student uses the following method.

step 1 use a measuring cylinder to measure out 100 cm3 of dilute hydrochloric acid

step 2 pour the acid into a beaker

step 3 measure the pH with a pH probe

step 4 add half a spatula of solid B and stir

step 5 repeat steps 3 and 4 until the pH stops changing.

i)
Give a safety precaution that should be taken during the experiment.

(1)

ii)

Give an improvement to step 4 that would produce more accurate results.

(1)

iii)
What is the most likely change in pH during the experiment?

  ☐ A from 1 to 7
  ☐ B from 1 to 12
  ☐ C from 7 to 12
  ☐ D from 12 to 1

(1)

iv)

If some methyl orange indicator is added to the acid in step 2, the mixture changes colour during the experiment.

State the colour change.

(2)

   colour at start in acid ....................................

   colour at end ..........................

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14b4 marks
b)
Concentrated hydrochloric acid can be broken down using electricity.

The apparatus that can be used is shown in Figure 6.

fig-6-q6b-1cho-1f-paper-1-nov-2021

Figure 6

i)
Give the name of the piece of apparatus labelled X.

(1)

ii)
The rod labelled Y in Figure 6 is made of graphite.

What is the name of this piece of apparatus?

  ☐ A electrode
  ☐ B electrolysis
  ☐ C electrolyte
  ☐ D electron

(1)

iii)
Give one reason why graphite is a suitable material to make Y.

(1)

iv)
Complete the balanced equation for the reaction that occurs.

(1)

..........HCl → H2+ Cl2

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151 mark

Below are five steps in the preparation of a soluble salt. The sentences are not in the correct order.

  1. Heat to evaporate most of the water
  2. Add solid copper(II) oxide until no more dissolves
  3. Measure out 25 cm3 of dilute sulfuric acid
  4. Leave in a warm place to cool and crystallise
  5. Filter to remove the excess solid

What is the correct order of the sentences?

(1)

  ☐ A 5, 1, 4, 3, 2 
  ☐ B 2, 5, 3, 1, 4
  ☐ C 3, 2, 5, 1, 4
  ☐ D 5, 1, 3, 2, 4

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161 mark

Silver nitrate solution and dilute hydrochloric acid react to product silver chloride solution and nitric acid.

What is the state symbol for the silver chloride produced?

(1)

  ☐ A g
  ☐ B aq
  ☐ C l
  ☐ D s

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17a2 marks

The scientist John Dalton lived over 200 years ago.

a)

John Dalton suggested an early model of atoms.

When Dalton first described atoms he said that

  • all elements are made of atoms
  • atoms are not formed of any smaller particles
  • all atoms of the same element are identical.

Give two differences between Dalton’s model of atoms and today’s model of atoms.

(2)

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17b2 marks
b)
Dalton also investigated different gases.

One of the gases that Dalton investigated was ethene.

The structure of one molecule of ethene is shown in Figure 8.

fig-2-q2b-1cho-1h-paper-1-nov-2021Figure 8

Give the molecular formula and the empirical formula of ethene.

(2)


molecular formula ............................................................................................

empirical formula ............................................................................................

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17c7 marks
c)
Another gas that Dalton investigated was chlorine.

Chlorine gas reacts with water.
The two products are a solution of hydrogen chloride and the substance HClO.

i)
Complete the balanced equation for this reaction, including the three missing state symbols.

(3)


 ................(..............) + ............... (..............) rightwards harpoon over leftwards harpoon for blank of ............... (..............) + HClO (aq)

ii)
Hydrogen chloride solution is acidic.

The formulae of four ions are shown in Figure 9.

H+                                                 H–                                                 Cl+                                             Cl–


Figure 9

Give the formula of the ion in Figure 9 that causes the hydrogen chloride solution to be acidic.

(1)
formula .............................................................................................

iii)

An acid reacts with an alkali.

Give the name of this type of reaction.

(1)

iv)
Describe what you would see when some copper carbonate powder is added to a beaker of dilute sulfuric acid.

(2)

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18
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Higher Only

A solution of sulfuric acid with a pH of 4 has a hydrogen ion concentration of 1 x 10-4 mol/dm3.

Another acid has a hydrogen ion concentration of 1 x 10-6 mol/dm3.

What is the pH of this acid?

(1)

  ☐ A 2
  ☐ B 3
  ☐ C 5
  ☐ D 6

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1a2 marks

Higher Only

X and Y are solutions of two different acids.

The concentration of acid in each solution, in mol dm−3, is the same.

Solution X has a pH of 3.40 and solution Y has a pH of 4.40.

i)
State what could be used to measure these pH values of 3.40 and 4.40.
(1)

ii)
What is the concentration of hydrogen ions in solution X compared with that in solution Y?
(1)
  ☐ A ten times lower
  ☐ B lower by a factor of 3.40 / 4.40
  ☐ C higher by a factor of 4.40 / 3.40
  ☐ D ten times higher

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1b5 marks

Higher Only

An experiment is planned to record the change in pH as a powdered base is added to 50 cm3 dilute hydrochloric acid.

 The method suggested is

   step 1 add dilute hydrochloric acid up to the 50 cm3 mark on a beaker
   step 2 add one spatula of the base and stir
   step 3 measure the pH of the mixture
   step 4 repeat steps 2 and 3 until the pH stops changing.
  
i)
State how you could change the method so that the amounts of dilute hydrochloric acid and of the base can be measured more accurately.
 
(2)
 
dilute hydrochloric acid .............................................................................................
 
base ...................................................................................................

ii)
During the experiment the pH changes from 2 to 10.
If phenolphthalein indicator is added at the beginning of the experiment, a colour change occurs as the base is added.
 
State the colour change that occurs.
 
(1)
 
colour at start .............................................................................................
 
colour at end .............................................................................................

iii)
Explain, in terms of the particles present, why the pH increases during the experiment.
 
(2)

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1c6 marks

Some properties of four solids, A, B, C and D, are shown in Figure 6.
The solids, in no particular order, are copper carbonate, copper oxide, magnesium metal and sodium hydroxide.

  A B C D
colour of solid black silver white green
observation when
solid is added to
water		 black solid
remains		 a few bubbles
appear on surface
of solid

solid dissolves
and forms
colourless
solution

 green solid
remains
pH of mixture of
solid added to
water		 7 8 13 7
observation when
solid is added to
dilute sulfuric acid		 on warming,
solid disappears
to form blue
solution		 effervescence
solid disappears
to form colourless
solution		 solid disappears
to form colourless
solution		 effervescence
solid disappears
to form blue
solution

Figure 6

Identify the solids A, B, C and D, explaining how the information in Figure 6 supports the identification of each solid.

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2a3 marks

Higher Tier Only 

Dilute hydrochloric acid is a strong acid.

i)
Explain why dilute hydrochloric acid is described as a strong acid.
(2)
ii)
1 cm3 of hydrochloric acid of pH 2 is made up to a volume of 10 cm3 with distilled water.
State the pH of the new solution.
(1)

pH = ..........................................................

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2b3 marks

Higher Tier Only 

Magnesium oxide reacts with dilute hydrochloric acid to produce magnesium chloride solution and water.

MgO (s) + 2HCl (aq) → MgCl2 (aq) + H2O (l)

Write the ionic equation for this reaction.

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2c5 marks

Higher Only

In an experiment magnesium hydroxide powder is added in 0.1 g portions to 25 cm3 of dilute hydrochloric acid until the magnesium hydroxide is just in excess.

Universal indicator paper can be used to test the pH of the solution after each addition of magnesium hydroxide.

i)
Give the name of an alternative piece of equipment that can be used to measure pH.
(1)
ii)
State and explain how the pH changes as the magnesium hydroxide is added to the dilute hydrochloric acid.
(4)

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3a2 marks

Higher Only

Copper carbonate reacts with dilute nitric acid.

i)

During the reaction the copper carbonate powder completely disappears.

State what can be deduced about the amount of acid used.

(1)

ii)
During the reaction, the pH of the mixture changed from 2 to 6.

By what factor has the concentration of the hydrogen ions in the mixture changed?

  ☐ A × 10 000
  ☐ B × 4
  ☐ C × 1⁄4
  ☐ D × fraction numerator 1 over denominator 10 space 000 end fraction

(1)

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3b2 marks

Using different reactants, a solution of copper sulfate was prepared.

Describe what should be done to obtain copper sulfate crystals from this copper sulfate solution.

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3c1 mark

Higher Only

When chloride ions are added to a pale blue solution containing copper ions, the mixture turns yellow.

This is a reversible reaction.

pale blue solution + chloride ions rightwards harpoon over leftwards harpoon for blank of yellow solution + water

What effect does the removal of chloride ions have on the colour of the yellow mixture?   

  ☐ A does not change colour
  ☐ B turns blue 
  ☐ C turns colourless
  ☐ D turns darker yellow

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3d
Sme Calculator4 marks

Higher Only

Hydrated copper sulfate has the formula CuSO4.5H2O.
The formula tells us that each mole of copper sulfate contains 5 moles of water.

A sample of CuSO4.5H2O was heated gently until all the water was removed to
form anhydrous copper sulfate, CuSO4.

CuSO4.5H2O → CuSO4 + 5H2O

The mass of water formed was 4.5 g.

Calculate the mass of hydrated copper sulfate that was heated.

(relative atomic masses: H = 1.0, O = 16.0;
relative formula mass: CuSO4.5H2O = 249.5)

mass of CuSO4.5H2O = ............................................................... g

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4a2 marks

Copper(II) chloride is soluble in water.

Calculate the mass of copper(II) chloride that needs to be dissolved in 100 cm3 of water to make a solution with concentration 50 g dm-3.

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4b1 mark

Higher Only

Give one change to the method in part a) that would result in a more concentrated solution.

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4c1 mark

Copper(II) chloride solution reacts with sodium hydroxide solution.
Sodium hydroxide is an alkali.

Define alkali.

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4d3 marks

Complete the symbol equation for the reaction by adding the state symbols.

CuCl2 (...) + 2NaOH (.....) → Cu(OH)2 (.....) + 2NaCl (.....)

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5a
Sme Calculator2 marks

A student wanted to find the volume of dilute sulfuric acid that would react with 25.0 cm3 of potassium hydroxide solution.

They used the equipment in Figure 1.

edx-3-1h-q5a-titration-equipment

Figure 1

Write the balanced symbol equation for the reaction.

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5b2 marks

Explain why universal indicator would not be a suitable indicator to be used in this titration.

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5c2 marks

The student carried out 4 titrations.

Figure 2 shows their results.

  Titration 1 Titration 2 Titration 3 Titration 4
Final burette reading (cm3) 30.40 33.80 33.60 46.10
Initial burette reading (cm3) 0.00 0.30 0.20 12.70
Volume of acid used (cm3) 30.40 33.50 33.40 33.40

Figure 2

Calculate the mean volume of acid.

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5d3 marks

The student uses this mean volume of acid to produce a salt solution in the conical flask.

Devise a plan to produce a sample of dry salt from this solution.

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