Acids Practice Questions

Question 1

4 marks

Acids and alkalis form ions when they dissolve in water. Indicators can be used to show whether a solution is acidic or alkaline.

(a)

Name the ion that all acids produce when they dissolve in water, and the ion that all alkalis produce when they dissolve in water.

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(b)

Complete the table to show the colour of each indicator in dilute hydrochloric acid and in sodium hydroxide solution. The litmus row has been done for you.

Indicator	Colour in dilute hydrochloric acid	Colour in sodium hydroxide solution
litmus	red	blue
methyl orange
phenolphthalein

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Question 2

3 marks

Bases and alkalis react with acids.

(a)

Which substance is an alkali?

Put a cross ( ☒ ) in the box next to your answer.

☐ A copper oxide

☐ B potassium hydroxide

☐ C calcium carbonate

☐ D zinc

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(b)

State what is meant by the term base.

/ 1

(c)

Name the type of reaction that takes place when an acid reacts with an alkali.

/ 1

Question 3

3 marks

A student adds a few pieces of zinc to dilute sulfuric acid in a test tube. The mixture fizzes and a gas is given off.

(a)

Name the salt formed in this reaction.

/ 1

(b)

Describe the chemical test for the gas given off, and state the positive result.

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Question 4

3 marks

Solubility rules can be used to decide whether a salt dissolves in water.

(a)

Which salt is insoluble in water?

Put a cross ( ☒ ) in the box next to your answer.

☐ A sodium carbonate

☐ B lead chloride

☐ C ammonium sulfate

☐ D potassium nitrate

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(b)

Use the solubility rules to complete the table by writing soluble or insoluble for each compound.

Compound	Soluble or insoluble in water
silver chloride
ammonium carbonate
barium sulfate
magnesium nitrate

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Question 0

4 marks

Zinc carbonate is an insoluble solid. It is added, a little at a time, to a beaker of warm dilute nitric acid until no more reacts.

(a)

Complete the word equation for the reaction.

zinc carbonate + nitric acid → .................... + .................... + ....................

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(b)

Write the balanced equation for this reaction. Formulae: zinc carbonate $\mathrm{ZnCO_3}$ , nitric acid $\mathrm{HNO_3}$ , zinc nitrate $\mathrm{Zn(NO_3)_2}$ .

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(c)

State one observation the student could make to show that the reaction has finished.

/ 1

Question 0

4 marks

A student investigates the change in pH when powdered calcium oxide is added to dilute hydrochloric acid.

The method used is:

step 1 pour dilute hydrochloric acid into a beaker up to the 50 cm³ mark
step 2 add one spatula of powdered calcium oxide and stir
step 3 measure the pH of the mixture using universal indicator paper
step 4 repeat steps 2 and 3 until the pH stops changing.

(a)

Name a piece of apparatus that would measure $50.0\ \mathrm{cm^3}$ of the dilute hydrochloric acid more accurately than a beaker or a measuring cylinder.

/ 1

(b)

Describe how the student uses the universal indicator paper in step 3 to find the pH of the mixture.

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(c)

Explain why the mixture is stirred in step 2.

/ 1

Question 0

4 marks

Solution A is dilute hydrochloric acid. Its pH is 1.0.

Solution B is propanoic acid of the same concentration as solution A. Its pH is 3.0.

Propanoic acid is a weak acid.

(a)

Explain, in terms of ions, what is meant by a weak acid.

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(b)

Compare the concentration of hydrogen ions in solution A with the concentration of hydrogen ions in solution B. Use the pH values in your answer.

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Question 0

3 marks

A student has $10\ \mathrm{cm^3}$ of dilute hydrochloric acid of pH 2. She adds distilled water until the total volume of the solution is $100\ \mathrm{cm^3}$ .

(a)

State the pH of the diluted acid.

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(b)

The student suggests using litmus to measure the pH of her solutions. Give two reasons why litmus is not suitable for measuring pH.

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Question 0

6 marks

Copper sulfate is a soluble salt. Copper oxide is an insoluble base.

Describe how to prepare pure, dry crystals of hydrated copper sulfate, starting from copper oxide powder and dilute sulfuric acid. Your answer should include how you know when enough copper oxide has been added, and how a water bath is used.

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Question 0

4 marks

Barium chloride solution is mixed with sodium sulfate solution in a beaker. A white precipitate forms.

(a)

Name the white precipitate.

/ 1

(b)

Describe how a pure, dry sample of the precipitate can be obtained from the mixture in the beaker.

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Question 0

4 marks

Potassium chloride is a soluble salt. It can be made from potassium hydroxide solution and dilute hydrochloric acid. Potassium hydroxide is a soluble base.

(a)

Explain why a titration must be used when preparing pure, dry potassium chloride from these two solutions.

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(b)

Name a suitable indicator for this titration and state the colour change seen at the end point, when the acid is added from the burette to the alkali in the conical flask.

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Question 0

4 marks

Acidic solutions in water are a source of hydrogen ions, $\mathrm{H^+}$ .

(a)

Zinc oxide reacts with dilute hydrochloric acid to form a solution containing zinc ions, $\mathrm{Zn^{2+}}$ .

Complete the balanced ionic equation for this reaction.

$\mathrm{ZnO + ........\ H^+ \rightarrow ................ + ................}$

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(b)

Write the ionic equation, including the ions that react, for the neutralisation of potassium hydroxide solution by dilute nitric acid.

/ 1

(c)

Magnesium reacts with dilute sulfuric acid to form a solution containing magnesium ions, $\mathrm{Mg^{2+}}$ , and a gas.

Write the balanced ionic equation for this reaction.

/ 1

Question 0

4 marks

A student adds powdered calcium hydroxide, $0.5\ \mathrm{g}$ at a time, to $50\ \mathrm{cm^3}$ of dilute hydrochloric acid in a beaker. The mixture is stirred after each addition and the pH is measured with a pH probe.

The results are shown in the table.

Total mass of calcium hydroxide added / g	0.0	0.5	1.0	1.5	2.0	2.5
pH of mixture	1.0	1.9	3.5	11.9	12.4	12.4

(a)

Explain, in terms of the ions present, why the pH of the mixture at the end of the experiment is 12.4.

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(b)

Explain why the pH does not change when the total mass added increases from $2.0\ \mathrm{g}$ to $2.5\ \mathrm{g}$ .

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Question 0

6 marks

Sodium sulfate is a soluble salt. A student is asked to prepare pure, dry crystals of sodium sulfate from sodium hydroxide solution and dilute sulfuric acid.

Describe a method the student could use. Your answer should include the apparatus used to measure the solutions and how crystals that are not contaminated by indicator are obtained.

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Question 0

4 marks

A bottle in a school laboratory is labelled dilute hydrochloric acid. Hydrochloric acid is a strong acid.

Explain how this acid can be described as both dilute and strong.

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Key Concepts in Chemistry

States of Matter & Mixtures

Chemical Changes

Extracting Metals & Equilibria

Groups in the Periodic Table

Rates of Reaction & Energy Changes

Fuels & Earth Science

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