CIE IGCSE Chemistry

Topic Questions

IGCSEChemistryCIETopic Questions7. Acids, Bases & Salts7.1 The Characteristic Properties of Acids & Bases

7.1 The Characteristic Properties of Acids & Bases

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1a3 marks

Zirconium (Zr) is a metal in Period 5. Its main oxidation state is +4.

The following are all zirconium atoms: Zr presubscript 40 presuperscript 90, Zr presubscript 40 presuperscript 91, Zr presubscript 40 presuperscript 92.

In terms of numbers of electrons, neutrons and protons, how are these three atoms the same and how are they different?


They are the same because ...


They are different because ...

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1b2 marks

Above 900°C, zirconium reacts with water to form zirconium(IV) oxide, ZrO2, and hydrogen. Write an equation for this reaction.

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1c4 marks

Extended Only

It is possible to determine whether zirconium(IV) oxide is acidic, neutral, basic or amphoteric using an acid and an alkali. Complete the table of possible results. If the oxide is predicted to react write ‘R’, if it is predicted not to react write ‘NR’.

if the oxide is predicted result with hydrochloric acid predicted result with aqueous sodium hydroxide
acidic    
basic    
neutral    
amphoteric    

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2a8 marks

Extended Only

Ethanoic acid is a colourless liquid at room temperature. It has the typical acid properties and forms compounds called ethanoates.

A pure sample of ethanoic acid is slowly heated from 0 oC to 150 oC and its temperature is measured every minute. The results are represented on the graph below.

heating-curve-ethanoic-acid

i)
Name the change that occurs in the region D to E.

[1]

ii)
What would be the difference in the region B to C if an impure sample had been used?

[1]

iii)
Sketch on the graph how the line would continue if the acid was heated to a higher temperature.

[1]

iv)
Complete the following table that compares the separation and movement of the molecules in regions C to D with those in E to F.

  C to D E to F
separation (distance
between particles)		    

movement of particles

 random and slow  
Can particles move apart to
fill any volume?		    

[5]

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2b2 marks

Complete the word equations for the reactions of ethanoic acid.

calcium + ethanoic acid → .......................................... +  ..........................................

 .......................................... + ethanoic acid → zinc ethanoate + water

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2c2 marks

Separate: Chemistry Only

Write the symbol equation for the reaction between ethanoic acid and sodium hydroxide.

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3a2 marks

Universal indicator is added to an aqueous solution of sodium oxide.

What colour change is observed?

from green to ________________

Give a reason for your answer.

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3b4 marks

Acids have characteristic properties.

Hydrochloric acid reacts with magnesium carbonate.
Name the products of this reaction and give the observations.

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42 marks

Separate: Chemistry and Extended Only

Some acids are described as weak acids.

State the meaning of the term weak acid.

weak    __________________

acid      __________________

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5a2 marks

Limestone is added to the blast furnace. The limestone is converted into calcium oxide and carbon dioxide. The reaction is endothermic.

                                                    CaCO3 rightwards arrow with heat on top  CaO + CO2

What type of oxide is calcium oxide?
Give a reason for your answer.

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5b1 mark

Sulfur dioxide is a pollutant in the air.

Sulfur trioxide dissolves in rainwater to form acid rain.


Which one of the following pH values could be the pH of acid rain? Draw a  circle around the correct answer.


                               pH 4      pH  7     pH 9     pH 13

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61 mark

Oxides of nitrogen are pollutants in the air.

Oxides of nitrogen are formed during the manufacture of nitric acid. Which one of the pH values could be the pH of nitric acid? Draw a circle around the correct answer.

                                      pH 1   pH 7   pH 10   pH 14

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7a2 marks

Aqueous ethanoic acid has chemical properties which are typical of acids.
Describe two chemical properties of aqueous ethanoic acid.

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7b1 mark

When carbon is completely burned in air, carbon dioxide is formed. Carbon dioxide forms a slightly acidic solution in water.

Which one of these pH values is the pH of a slightly acidic solution? Draw a circle around the correct answer.

                                              pH 6     pH 7   pH 8    pH 10

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1a
Sme Calculator3 marks

Hydrogen reacts with the halogens to form hydrogen halides.

Bond energy is the amount of energy, in kJ, that must be supplied (endothermic) to break one mole of a bond.

 
bond bond energy in kJ/mol 
H-H +436
Cl-Cl +242
H-Cl +431
 

Use the above data to show that the following reaction is exothermic.

 
H─H + Cl─Cl → 2H─Cl
 

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1b5 marks

They react with water to form acidic solutions.

 
HCl + H2O rightwards harpoon over leftwards harpoon H3O+ + Cl–
 
HF + H2O rightwards harpoon over leftwards harpoon H3O+ + F–
 
i)
Explain why water behaves as a base in both of these reactions.
 
[2]
 
ii)
At equilibrium, only 1% of the hydrogen chloride exists as molecules, the rest has formed ions. In the other equilibrium, 97% of the hydrogen fluoride exists as molecules, only 3% has formed ions.
 
What does this tell you about the strength of each acid?
 
[2]
 
iii)
How would the pH of these two solutions differ?
 
[1] 

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2a5 marks

Ethylamine is a weak base and sodium hydroxide is a strong base.

i)
In terms of proton transfer, explain what is meant by the term weak base.

[2]

ii)
Given aqueous solutions of both bases, describe how you could show that sodium hydroxide is the stronger base. How could you ensure a ‘fair’ comparison between the two solutions? 
[3]

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2b4 marks

Ethylamine reacts with acids to form salts.

CH3CH2NH2 + HCl → CH3CH2NH3Cl
               ethylammonium chloride

i)
Complete the equation for the reaction between sulfuric acid and ethylamine.

......CH3CH2NH2 + ............ → .........................

Name the salt formed.
[3]

ii)
Amines and their salts have similar chemical properties to ammonia and ammonium salts.

Suggest a reagent that could be used to displace the weak base, ethylamine, from its salt ethylammonium chloride.
[1]

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2c5 marks

Gases diffuse, which means that they move to occupy the total available volume.

i)
Explain, using kinetic particle theory, why gases diffuse.
[2] 
ii)

When the colourless gases hydrogen bromide and ethylamine come into contact, a white solid is formed.

CH3CH2NH2 (g) + HBr (g) → CH3CH2NH3Br (s)
               white solid

The following apparatus can be used to compare the rates of diffusion of the two gases ethylamine and hydrogen bromide.

CIE IGCSE 7.1 Q3

Predict at which position, A, B or C, the white solid will form. Explain your choice.

[3]

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3a6 marks

Sulfuric acid and malonic acid are both dibasic acids. One mole of a dibasic acid can form two moles of hydrogen ions.

H2SO4 → 2H+ + SO42–

Dibasic acids can form salts of the type Na2X and CaX.

Malonic acid is a white crystalline solid which is soluble in water. It melts at 135 °C. The structural formula of malonic acid is given below. It forms salts called malonates.

CH2(COOH)2 or HOOC–CH2 –COOH

i)
How could you determine if a sample of malonic acid is pure?

Technique used ..........................................................................................................

Result if pure .........................................................................................................
[2]
ii)
What is the molecular formula of malonic acid?
[1]

iii)
When malonic acid is heated there are two products, carbon dioxide and a simpler carboxylic acid. Deduce the name and molecular formula of this acid.
[2]

iv)

Malonic acid reacts with ethanol to form a colourless liquid which has a ‘fruity’ smell.
Its structural formula is given below.

screen-shot-2022-09-05-at-21-26-48

What type of compound contains the group which is circled?

[1] 

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3b3 marks
i)
Suggest why a solution of malonic acid, concentration 0.2 mol /dm3, has a higher pH than one of sulfuric acid of the same concentration.
[1]
ii)
Describe a test, other than measuring pH, which can be carried out on both acid solutions to confirm the explanation given in (b)(i) for the different pH values of the two acids.
[2]

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3c7 marks

Complete the following equations for reactions of these two acids.

i)
sodium hydroxide + malonic acid → ........................ .......................... + ....................
[1]
ii)
CuO + H2SO4 → .................... + ....................
[2]
iii)
Mg + CH2(COOH)2 → .................... + ....................
[2]
iv)
K2CO3 + H2SO4 → .................... + .................... + ....................
[2]

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4a1 mark

Ethylamine, CH3–CH2–NH2, is a base which has similar properties to ammonia.

In aqueous ethylamine, there is the following equilibrium.

CH3–CH2–NH2 + H2O rightwards harpoon over leftwards harpoonCH3–CH2–NH3+ + OH–

Explain why water is behaving as an acid in this reaction.

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4b3 marks

Given aqueous solutions of ethylamine and sodium hydroxide, describe how you could show that ethylamine is a weak base like ammonia and not a strong base like sodium hydroxide.

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4c2 marks

Ethylamine, like ammonia, reacts with acids to form salts.

CH3–CH2–NH2 + HCl → CH3–CH2–NH3Cl
                                                        ethylammonium chloride

Suggest how you could displace ethylamine from the salt, ethylammonium chloride.

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4d2 marks

Explain the chemistry of the following reaction:

When aqueous ethylamine is added to aqueous iron(III) chloride, a brown precipitate is formed.

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5a1 mark

Silicon(IV) oxide, SiO2, and zirconium(IV) oxide, ZrO2, are both macromolecules. They have similar physical properties but silicon(IV) oxide is acidic and zirconium(IV) oxide is amphoteric.

Define the term macromolecule.

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5b4 marks
i)
Predict three physical properties of these two oxides.
[3]

ii)
Name an element which has the same physical properties as these two oxides.
[1]

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5c3 marks
i)
Name a reagent that reacts with the oxides of both elements.

[1]

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

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

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

[2]

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6a6 marks

Sulphuric acid is a typical strong acid.

Change the equations given into a different format.

i)
Mg + H2SO4 → MgSO4 + H2
Change into a word equation.
[1]

ii)
Lithium oxide + sulphuric acid → lithium sulphate + water
Change into a symbol equation.
[2]

iii)
CuO + 2H+ → Cu2+ + H2O
Change the ionic equation into a symbol equation.
[2]

iv)
Na2CO3 + H2SO4 → Na2SO4 + CO2 + H2O
Change into a word equation.
[1]

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6b2 marks

When sulphuric acid dissolves in water, the following reaction occurs.

H2SO4 + H2O → HSO4– + H3O+

Explain why water is behaving as a base in this reaction.

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6c2 marks

Sulphuric acid is a strong acid, ethanoic acid is a weak acid.

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

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7a4 marks

Antimony oxide is a white powder which is insoluble in water. Describe how you would find out if it is a basic, an acidic or an amphoteric oxide.

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7b4 marks

When antimony chloride is added to water, a faint white precipitate forms and the mixture slowly goes cloudy.

forward 

SbCl3 (aq) + H2O (l) rightwards harpoon over leftwards harpoon 2HCl (aq) + SbOCl (s)

colourless  backward      white 

i)
Explain why after some time the appearance of the mixture remains unchanged.

[2]

ii)
When a few drops of concentrated hydrochloric acid are added to the mixture, it changes to a colourless solution. Suggest an explanation.

[1]

iii)
Suggest how you could make the colourless solution go cloudy.

[1]

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8a3 marks

The major use of sulfur dioxide is to manufacture sulfuric acid.

Complete the following description of the manufacture of sulfuric acid.


Sulfur dioxide reacts with .............................. to form sulfur trioxide.

The above reaction is catalysed by ................................................. .

The optimum temperature for this reaction is .............................. °C.

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8b3 marks
i)
Define the term acid.

[1]

ii)
Sulfuric acid is a strong acid. Ethanedioic acid is a weak acid.
Given solutions of both acids, how could you show that sulfuric acid is a strong acid and ethanedioic acid is a weak acid?

Method

[1]

   Result for each acid

[1]

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8c
Sme Calculator5 marks

20.0 cm3 of sulfuric acid, concentration 0.30 mol / dm3, was added to 40 cm3 of sodium hydroxide, concentration 0.20 mol / dm3.


2NaOH + H2SO4 → Na2SO4 + 2H2O

i)
How many moles of H2SO4 were added?

[1]

ii)
How many moles of NaOH were used?

[1]

iii)
Which reagent is in excess? Give a reason for your choice.

Reagent in excess 
[1]
Reason

[1]

iv)
Is the pH of the final mixture less than 7, equal to 7 or more than 7?
[1]

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1a3 marks

Sulfuric acid is a strong acid. In aqueous solution, it ionises as shown below.

H2SO4  → 2H+ + SO42–

i)
What is meant by the term acid?

[1]

   Sulfurous acid, H2SO3, is a weak acid.

ii)
State the difference between a weak acid and a strong acid.

[2]

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1b4 marks

Sulfurous acid forms salts called sulfites and contain the ion SO32-

When barium nitrate solution is added to aqueous sulfurous acid, a white precipitate, A, forms. Bromine water changes from brown to colourless when added to aqueous sulfurous acid. 

Bromine oxidises sulfurous acid. When this solution is tested with acidified barium nitrate a different white precipitate B is formed. 

i)
Identify the white precipitate, A.
[1]
ii)
Identify the white precipitate, B.
[1]
iii)
Write an ionic equation for the reduction of the bromine molecule.
[1]
iv)
Name the product formed by the oxidation of sulfurous acid.

[1]

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1c3 marks

Complete the following word equations.

i)
magnesium hydroxide + dilute sulfuric acid

   .......................................................................................................................................

[1]

ii)
zinc + dilute sulfuric acid

   .......................................................................................................................................

[1]

iii)
copper carbonate + dilute sulfuric acid

   ......................................................................................................................................

[1]

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1d5 marks

Write equations for the reaction of dilute sulfuric acid with each of the following.

i)
ammonia
[1]

ii)
sodium hydroxide
[2]

iii)
iron
[2]

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2a1 mark

This question is concerned with the following oxides.

   aluminium oxide
   carbon monoxide
   copper(II) oxide
   silicon(IV) oxide
   sodium oxide
   sulfur dioxide
   zinc oxide

Choose one oxide from the above list to match each of the following descriptions. An oxide may be used once, more than once or not at all.

This oxide does not react with acid or alkali.

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2b1 mark

This oxide reacts with water to give a strong alkali solution.

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2c1 mark

This oxide is used as a bleach.

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2d1 mark

Extended Only

This oxide is amphoteric.

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2e1 mark

This oxide has a giant covalent structure.

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2f1 mark

This oxide is soluble in water and it is acidic.

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3a5 marks

Match the following pH values to the solutions given below

1    3    7    10    13 


The solutions all have the same concentration.

Solution  pH
aqueous ammonia, a weak base ...............
dilute hydrochloric acid, a strong acid ...............
aqueous sodium hydroxide, a strong base ...............
aqueous sodium chloride, a salt ...............
dilute ethanoic acid, a weak acid ...............

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3b1 mark

Separate: Chemistry and Extended Only

Explain why solutions of hydrochloric acid and ethanoic acid with the same concentration, in mol/dm3, have a different pH.

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3c2 marks

Separate: Chemistry and Extended Only

Measuring pH is one way of distinguishing between a strong acid and a weak acid.

Describe another method.

method .......................................................................................................................................

......................................................................................................................................................

results ........................................................................................................................................

......................................................................................................................................................

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4a4 marks

Extended Only

This question is concerned with the following oxides.

sulfur dioxide
carbon monoxide
lithium oxide
aluminium oxide
nitrogen dioxide
strontium oxide

i)
Which of the above oxides will react with hydrochloric acid but not with aqueous sodium hydroxide?
[1]

ii)
Which of the above oxides will react with aqueous sodium hydroxide but not with hydrochloric acid?
[1]

iii)
Which of the above oxides will react with both hydrochloric acid and aqueous sodium hydroxide?
[1] 

iv)
Which of the above oxides will not react with hydrochloric acid or with aqueous sodium hydroxide?
  [1]

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4b5 marks

Two of the oxides are responsible for acid rain.

Identify the two oxides and explain their presence in the atmosphere.

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4c3 marks

Lithium oxide is an ionic compound.

i)
Identify another ionic oxide in the list in part a)
[1]
ii)
Draw a diagram which shows the formula of lithium oxide, the charges on the ions and the arrangement of the valency electrons around the negative ion.

Use x to represent an electron from an atom of oxygen.
Use o to represent an electron from an atom of lithium.
[2]

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5a2 marks

Four bottles were known to contain aqueous ammonia, dilute hydrochloric acid, sodium hydroxide solution and vinegar, which is dilute ethanoic acid. The bottles had lost their labels. The pH values of the four solutions were 1, 4, 10 and 13.

Complete the table.

solution pH
aqueous ammonia   
dilute hydrochloric acid  
sodium hydroxide solution  
vinegar  

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5b2 marks

When nitric acid is added to water the following reaction occurs.

HNO3 + H2O → NO3– + H3O+

Give the name and the formula of the particle which is transferred from nitric acid to water.


name

formula

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5c4 marks

Extended Only

This question is concerned with the following oxides.

aluminium oxide Al2O3
calcium oxide CaO
carbon dioxide CO2
carbon monoxide CO
magnesium oxide  MgO
sulphur dioxide SO2


i)
Which of the above oxides will react with hydrochloric acid but not with aqueous sodium hydroxide?
[1]
ii)
Which of the above oxides will react with aqueous sodium hydroxide but not with hydrochloric acid?
[1]
iii)
Which of the above oxides will react both with hydrochloric acid and with aqueous sodium hydroxide?
[1]
iv)
Which of the above oxides will react neither with hydrochloric acid nor with aqueous sodium hydroxide?
[1]

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6a1 mark

Sulfuric acid is a strong acid. Hexanesulfonic acid is also a strong acid. It has similar properties to sulfuric acid.

The formula of the hexanesulfonate ion is C6H13SO3–.


The formula of the barium ion is Ba2+. What is the formula of barium hexanesulfonate?

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6b4 marks

Complete the following equations.

i)
Magnesium + hexanesulfonic acid → ............................. ......................... + ......................... 
[1]
ii)
Calcium oxide + hexanesulfonic acid → ............................. ......................... + ......................... 
[1]
iii)
.....C6H13SO3H + Na2CO3 → ............................. + ............ + ............
[2]

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6c5 marks

Separate: Chemistry and Extended Only

i)
Sulfuric acid is a strong acid. You are given aqueous sulfuric acid, concentration 0.1 mol /dm3 , and aqueous hexanesulfonic acid, concentration 0.2 mol /dm3. Describe how you could show that hexanesulfonic acid is also a strong acid.
[2]

ii)
Deduce why, for a fair comparison, the two acid solutions must have different concentrations. 

[1]

iii)
Explain the terms strong acid and weak acid.
[2]

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7a1 mark

A student investigates the reaction of small pieces of zinc with dilute sulfuric acid at 20 °C. The zinc is in excess.
Sulfuric acid is a compound.

Define the term compound.

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7b1 mark

State the formula of the ion that is present in an aqueous solution of all acids.

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7c1 mark

A few drops of the indicator methyl orange are added to aqueous dilute sulfuric acid. State the colour change observed

from orange to ____________________

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7d
Sme Calculator2 marks

The formula of sulfuric acid is H2SO4.
Complete Table 1 to calculate the relative molecular mass of sulfuric acid.
                          
                                                       Table 1q4civ_specimen-paper-0620-03-cie-igcse-chemistry

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8a1 mark

Aqueous sodium hydroxide is a base.

Complete this sentence about the different types of bases.
Bases are metal hydroxides or metal _______________________

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8b4 marks

Describe the reaction of aqueous sodium hydroxide with:

i)
A named acid

ii)
An ammonium salt

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8c1 mark

Ammonia is a soluble base.
Draw a circle around the pH value of aqueous ammonia.

                            pH 1    pH 5    pH 7    pH 10

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9a1 mark

Magnesium, calcium and strontium are Group II elements.

Calcium reacts with cold water to form two products:

  • a colourless gas, P, which ‘pops’ with a lighted splint
  • a weakly alkaline solution, Q, which turns milky when carbon dioxide is bubbled through it.

Name gas P.

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9b1 mark

Identify the ion responsible for making solution Q alkaline.

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9c1 mark

Suggest the pH of solution Q.

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9d2 marks

Write a symbol equation for the reaction of calcium with cold water.

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10a1 mark

Separate: Chemistry and Extended Only

Sulfuric acid has many uses. Sulfuric acid is a strong acid.

Define the term acid.

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10b1 mark

Separate: Chemistry and Extended Only

Define the term strong acid.

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11a1 mark

Separate: Chemistry and Extended Only

Ammonia reacts with water to form ions.

                                          NH3 + H2Orightwards harpoon over leftwards harpoonNH4+ + OH–

How does this equation show that ammonia, NH3, behaves as a base?

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11b1 mark

Separate: Chemistry and Extended Only

Aqueous ammonia is described as a weak base.
Suggest the pH of aqueous ammonia.

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11c1 mark

Aqueous sodium hydroxide, NaOH (aq), is a strong alkali that reacts with dilute sulfuric acid exothermically.
What type of reaction is this?

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12a1 mark

Separate: Chemistry and Extended Only

Ethanoic acid is a weak acid and hydrochloric acid is a strong acid.
Both ethanoic acid and hydrochloric acid dissociate in aqueous solution.

Define the term acid.

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12b2 marks

Separate: Chemistry and Extended Only

The chemical equation shows the changes which occur when the strong acid, hydrochloric acid, is added to water.

                                      HCl (aq)rightwards arrowH+ (aq) + Cl– (aq)

Complete the chemical equation to show the changes which occur when the weak acid, ethanoic acid, is added to water.

CH3COOH (aq)  ______________________________

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