AQA GCSE Chemistry

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GCSEChemistryAQATopic Questions4. Chemical Changes4.2 Reactions of Acids

4.2 Reactions of Acids

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1a1 mark

This question is about the reactions of metals with acid.

Complete the general word equation for the reaction of a metal with an acid. 

Metal + acid → __________ + hydrogen

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1b2 marks

When metals react with acid, hydrogen gas is formed.

Describe the test for hydrogen, including the expected observation for a positive test.

Test: ______________________________ 

Positive result: ______________________________

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1c1 mark

Magnesium sulfate can be produced by the reaction of magnesium with an acid.

Which acid should the student use to produce magnesium sulfate?

Tick (✓) one box.

Hydrochloric acid  
Nitric acid  
Sulfuric acid  

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1d1 mark

Magnesium sulfate is made from the magnesium ion, Mg2+, and the sulfate ion, SO42–.

Write the chemical formula for magnesium sulfate.

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2a1 mark

This question is about acids, bases and salts.

A student reacts zinc carbonate with nitric acid.

Which salt is formed during this reaction?  

Tick (✓) one box. 

Zinc   
Zinc chloride   
Zinc nitrate  
Zinc oxide  

 

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2b2 marks

Complete the sentences. 

Choose answers from the box.

 
a colour change electrolysis a pungent smell
decomposition fizzing neutralisation oxidation
 

__________________ can be observed when zinc carbonate reacts with nitric acid.

 

This is due to the __________________ reaction releasing carbon dioxide gas.

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2c1 mark

The reaction of zinc carbonate with nitric acid can be represented with a balanced symbol equation.

Balance the symbol equation for this reaction. 

ZnCO3 + ___ HNO3 → Zn(NO3)2 + ___ H2O + CO2 

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3a1 mark

Copper oxide reacts with hydrochloric acid to form a salt and water.

What is the name of the salt that is formed?

Copper ________________

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3b1 mark

What type of reaction happens when copper oxide reacts with hydrochloric acid? 

Draw a circle around the correct reaction type. 

Combustion Precipitation Thermal decomposition Neutralisation

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3c1 mark

A student added an excess of copper oxide to warm dilute hydrochloric acid.

Describe how the student removed any unreacted solid copper oxide.

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3d3 marks

Complete the sentences. 

Choose answers from the box.

 
boiling  salt  water
melting  crystallisation
 

The student extracts the _______________ from the aqueous salt solution by _______________. 

This involves heating the solution until it is _______________. 

The solution is then left until only the salt remains

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4a1 mark

This question is about acids, bases and the pH scale.

Which ions make a solution alkaline?

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4b3 marks

Match the pH value to the description. 

Draw one line from each pH value to the correct description.

 
aqa-gcse-4-2e-q4b-ph-value-match-

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4c2 marks

pH can be measured in different ways.

What do each of the following sentences describe? 

One way of measuring pH involves a chemical that changes colour: _______________ 

Another way of measuring pH involves a piece of equipment that gives a more accurate pH reading: _______________

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4d4 marks

A student has three unlabelled bottles containing clear liquids.

The liquids are known to be dilute nitric acid, dilute sodium hydroxide and water.

Explain how the student could use universal indicator to determine the contents of each bottle?

Your answer should include expected observations.

Method: ____________________ 

Dilute nitric acid: ____________________ 

Dilute sodium hydroxide: ____________________ 

Water: ____________________

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4e2 marks

In a neutralisation reaction, H+ ions react with OH– ions to produce water.

Write the ionic equation of neutralisation.

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5a3 marks

This question is about strong and weak acids.

Use the information in Table 1 to help you answer all questions.

Table 1

  Nitric acid Sodium hydroxide
Type Strong acid Strong alkali
Ions in solution H+        NO3– Na+        OH–
pH 1 14
Colour with universal indicator Red Purple

Complete the sentences. 

The __________ ions in nitric acid make it acidic. 

The __________ ions in sodium hydroxide make it alkaline. 

Acids have a pH value that is __________ the pH value of alkalis.

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5b1 mark

Draw a ring around the correct answer to complete this sentence.

 

Weak acids and weak alkalis are

completely

not

partially
ionised in water.

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5c1 mark

The apparatus used to find the volume of sodium hydroxide solution that reacts with 25.0 cm3 of nitric acid is shown in Figure 1.

Figure 1

aqa-gcse-4-2e-q5c-basic-titration

What technique is shown in Figure 1?

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5d
Sme Calculator1 mark

A student completed the experiment shown in part (c) five times. The student's results are shown in Table 1.

Table 1

Titration

1

2

3

4

5

Volume of alkali added in cm3

21.1

21.9

21.0

21.1

21.7

How did the student know when enough sodium hydroxide had been added to neutralise the nitric acid?

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5e
Sme Calculator2 marks

Use three results to calculate the mean volume of sodium hydroxide reacted with the nitric acid.

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6a
Sme Calculator2 marks

25.0 cm3 of hydrochloric acid was titrated against a sodium hydroxide solution of 0.100 mol / dm3.

The average titre of sodium hydroxide solution required for this reaction was 17.3 cm3. 

Calculate the number of moles of the NaOH. 

Use the equation: 

moles space equals space concentration space left parenthesis in space mol space divided by space dm cubed right parenthesis space cross times space volume space left parenthesis in space dm cubed right parenthesis

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6b
Sme Calculator1 mark

The ratio of hydrochloric acid to sodium hydroxide is 1 : 1.

HCl + NaOH → NaCl + H2O

State the number of moles in the 25.0 cm3 of hydrochloric acid.

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6c
Sme Calculator1 mark

What is the concentration of the hydrochloric acid?

Use the equation:  

Concentration = fraction numerator moles over denominator volume space left parenthesis in space dm cubed right parenthesis end fraction

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1a1 mark

This question is about the reactivity of metals.

One method that can be used to determine the order of reactivity of metals is to add the metals to cold water and to dilute hydrochloric acid.

The observations made when strips of four metals are added separately to cold water and to dilute hydrochloric acid are shown in Table 1.

Table 1

Metal Observation with cold water Observation with dilute hydrochloric acid
Magnesium Bubbles very slowly Bubbles very quickly
Platinum No change Not done
Potassium Bubbles very quickly, catches fire Not done
Zinc No change Bubbles very slowly

 

One reason for not completing the reaction of platinum with dilute hydrochloric acid is the high cost of platinum (roughly £25 per gram). 

Suggest how the reaction of platinum with dilute hydrochloric acid could be completed without increasing the cost of the experiment.

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1b2 marks

Explain why the experiment with potassium and dilute hydrochloric was not completed.

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1c2 marks

Explain why it is not possible to produce a reactivity series using just the observations with cold water.

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1d4 marks

Magnesium reacts slowly with cold water but quickly with dilute hydrochloric acid. 

Explain two reasons why the reaction with cold water is slower than the reaction with hydrochloric acid.

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2a4 marks

This question is about chemical analysis.

Two students have solid powders of three metal compounds, X, Y and Z.

  • Compound X is a black powder.
  • Compound Y is a grey powder.
  • Compound Z is a white powder.

The students both use the same method for their first experiment.

  1. Measure 1.0 g of each powder into a separate test tube
  2. Add 5.0 cm3 of dilute sulfuric acid into each test tube
  3. Record any observations

The observation of both students are shown in Table 1.

Table 1

Sulfuric acid test Student 1 observation Student 2 observation
Compound X Goes black Produces a blue solution
Compound Y Lots of fizzing and gets hot Effervescence 
Compound Z Lots of fizzing Very effervescent

 

Both student's observations for compound X are correct, however student 1 did not leave the reaction to stand for enough time to see the blue solution.

Suggest the identity of compound X. Justify your answer, including a balanced equation. 

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2b2 marks

Student 1 concludes that compounds Y and Z are metal carbonates because they fizz lots.

Evaluate student 1's conclusion.

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2c2 marks

The students burn a small amount of compounds Y and Z in a blue Bunsen flame. 

The students forget to record the results but they know one compound gives a white flame and the other gives a yellow flame. 

Student 1 suggests that compound Y is magnesium and student 2 suggests that compound Z is magnesium oxide. 

Which student is correct? Explain your reasoning using the observations from both experiments.

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2d3 marks

Both students agree that compound Z contains sodium. 

Student 1 thinks that it is sodium carbonate while student 2 thinks it is sodium hydrogen carbonate.

Sodium carbonate and sodium hydrogen carbonate are both basic.

Explain how the students could use universal indicator solution to determine the identity of compound Z.

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3a2 marks

Sodium hydroxide is a strong alkali.

Explain what is meant by a strong alkali.

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3b1 mark

Sodium hydroxide can be neutralised with citric acid. 

Write the word equation for this reaction.

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3c4 marks

A student neutralised a 0.125 mol / dm3 sodium hydroxide solution with citric acid. 

3NaOH + C6H8O7 → 3H2O + Na3C6H5O7 

This is the method used.

  • Pipette 25 cm3 of sodium hydroxide solution into a conical flask.
  • Add a few drops of universal indicator to the sodium hydroxide solution.
  • Using a measuring cylinder, add 20 cm3 of 0.050 mol / dm3 citric acid solution.

Explain why this method will not fully neutralise the sodium hydroxide solution.

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3d1 mark

Explain why litmus would not be a suitable indicator for this reaction.

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3e2 marks

The neutralisation of sodium hydroxide by citric acid can be completed by titration. 

Explain why a pipette would be used to measure the sodium hydroxide solution but a burette would be used to measure the citric acid solution. 

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4a3 marks

This question is about hydrochloric acid.

Hydrochloric acid has some domestic uses such as cleaning tiles and rust.

It is recommended that dilute hydrochloric acid is used in these situations.

What is the difference between the pH of dilute hydrochloric acid compared to the pH of concentrated hydrochloric acid? 

Give a reason for your answer.    

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4b
Sme Calculator2 marks

A solution of hydrochloric acid, with a concentration of 1.5 g / dm3, has a pH value of 1.45. 

Predict the pH value when it is diluted to make a solution with a concentration of 0.015 g / dm3. Explain your reasoning.

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4c1 mark

The reaction of hydrochloric acid with sodium carbonate solution is an example of a neutralisation reaction. 

Write the ionic equation, including state symbols, for neutralisation.

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4d3 marks

A student plans to complete a titration experiment using hydrochloric acid and sodium hydroxide. 

They have a choice of three possible indicators:

  • Methyl orange
  • Phenolphthalein
  • Universal indicator 

Evaluate the suitability of each indicator for this titration.

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5a3 marks

This question is about the preparation of magnesium sulfate.

A group of students are asked to prepare a sample of magnesium sulfate.

The students suggest four possible ways to do this:

  1. Magnesium + sulfuric acid
  2. Magnesium carbonate + sulfuric acid
  3. Magnesium hydroxide + sulfuric acid
  4. Magnesium oxide + sulfuric acid

Which of the student's suggestions can be classed as a redox reaction? Justify your choice including relevant equations.

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5b1 mark

Explain which reaction produces the most hazardous products.

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5c6 marks

Describe how to prepare a sample of magnesium sulfate using suggestion 2.

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6a1 mark

This question is about titrations.

Phenolphthalein is a common indicator for the titration of sodium hydroxide with hydrochloric acid because it is colourless in acidic and neutral conditions but pink / purple in basic conditions.

Suggest why an indicator is required for the titration of hydrochloric acid with sodium hydroxide.

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6b5 marks

An experiment was completed titrating 25.0 cm3 of the hydrochloric with 0.100 mol / dm3 sodium hydroxide solution. 

The titration results are shown in Table 1. 

Table 1
 
 

Rough

Run 1

Run 2

Run 3

Initial burette reading / cm3 

0.00

0.00

23.30

0.05

Final burette reading / cm3 

24.15

23.30

46.65

23.15
 

Calculate the concentration of the hydrochloric acid. 

Use only the student’s concordant results. 

Concordant results are those within 0.10 cm3 of each other. 

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1a1 mark

Figure 1 shows a bottle of vinegar which is used to flavour food. 

Vinegar is an aqueous solution of ethanoic acid, CH3COOH.

Figure 1 

4-2-reactions-of-acids-medium-q1a

Ethanoic acid is described as a weak acid.

What is the ion present in aqueous solutions of all acids?

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1b5 marks

Discuss the difference in pH between a weak acid and a strong acid of the same concentration.

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1c5 marks

Figure 2 shows the apparatus used to find the concentration of ethanoic acid in vinegar.

Figure 2 

aqa-gcse-4-2m-q1c-concentration-of-vinegar-experiment

27.00 cm3 of a 1.0 mol dm-3 solution of NaOH was required to neutralise 25.00 cm3 of vinegar.

Calculate the concentration of ethanoic acid in the vinegar.

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2a2 marks

The balanced chemical equation between iron and hydrochloric acid is:

Fe (s) + 2 HCl (aq) → FeCl2 (aq) + _____ (g)

What is the name and symbol of the missing product?

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2b1 mark

What class of compound is the other product in the reaction?

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2c6 marks

Describe a suitable method for separating the FeCl2.

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2d4 marks

State what type of reaction this is and explain, using appropriate half equations the species being oxidised and those being reduced.

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3a2 marks

This question is about alkalis and bases.

Give the name and formula of the ion present in aqueous solutions of all alkalis.

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3b3 marks

Explain the difference between the terms base, alkali and alkaline solution.

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3c1 mark

Metals, metal hydroxides and metal oxides can neutralise acids. 

Name one other type of compound that can neutralise an acid.

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3d1 mark

Write the simplest ionic equation which represents a neutralisation reaction.

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4a2 marks

This question is about acids and alkalis.

A dilute solution of hydrochloric acid is considered a strong acid.

Justify how an acid can be described as both strong and dilute.

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4b2 marks

A 1.0 × 10−4 mol/dm3 solution of HCl has a pH of 4.0

What is the pH of a 1.0 × 10−6 mol/dm3 solution of the same acid? 

Explain your answer.

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5a4 marks

Sodium hydroxide neutralises sulfuric acid in the following reaction:

2NaOH + H2SO4 → Na2SO4 + 2H2O

Sulfuric acid is a strong acid.

Explain what the term “strong acid” means, discussing how the strength of an acid is linked to its pH value.

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5b2 marks

Write down the ionic equation for this neutralisation reaction and include the state symbols.

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5c4 marks

A chemist used a volumetric pipette to add 25.0 cm3 of a solution of sodium hydroxide of unknown concentration to a conical flask.

The chemist then carried out a titration to find out the volume of 0.150 mol/dm3 sulfuric acid needed to neutralise the sodium hydroxide.

Describe how the chemist would complete the titration.

You should state a suitable indicator and give the colour change that would be observed.

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