GCSE Combined Science Acids, electrolysis & salts questions by topic

A cleaner has a pH of about 12 on its label.

1. (a)State whether the cleaner is acidic, alkaline or neutral.[1]
2. (b)State which ion all alkalis release when dissolved in water.[1]
3. (c)Complete the sentence: neutralisation pairs hydrogen ions with ______ ions to make water.[1]
4. (d)Name the salt made when hydrochloric acid neutralises sodium hydroxide.[1]

Magnesium ribbon is dropped into dilute sulfuric acid and fizzes.

1. (a)Write the word equation for the reaction.[2]
2. (b)Name the gas and describe its test with a lighted splint.[2]

Name the salt in each reaction, or state the reaction family.

1. (a)Hydrochloric acid + potassium hydroxide →[1]
2. (b)Nitric acid + calcium carbonate → calcium nitrate + water + carbon dioxide. Name the salt family nitric acid always gives.[1]
3. (c)Sulfuric acid + zinc oxide →[1]
4. (d)State why farmers spread calcium hydroxide (lime) on fields.[1]

These steps of the salt-making practical are jumbled: filter; warm the dilute acid; cool the concentrated solution; add the insoluble base in excess; evaporate until crystals just form at the edges.

1. (a)Write the five steps in the correct order.[2]
2. (b)Name the residue left on the filter paper when copper(II) oxide is the base.[1]
3. (c)State one safety precaution for this practical.[1]

Predict the products of three acid reactions.

1. (a)Calcium carbonate + nitric acid →[2]
2. (b)Explain why copper metal does not react with dilute sulfuric acid, even though zinc does.[2]
3. (c)Iron oxide reacts with hydrochloric acid. Name the salt formed.[1]

A student prepares zinc sulfate crystals from zinc carbonate and dilute sulfuric acid.

1. (a)Explain why the zinc carbonate is added until some no longer dissolves.[1]
2. (b)Explain why the mixture is filtered before evaporation.[1]
3. (c)Explain why the filtrate is not evaporated to complete dryness.[1]
4. (d)Describe how crystals are obtained once the concentrated solution has cooled.[2]

Predict the electrode products when aqueous solutions are electrolysed with inert electrodes.

1. (a)Aqueous magnesium sulfate: name the product at the cathode and at the anode.[2]
2. (b)Copper chloride solution: name the product at the cathode and at the anode.[2]
3. (c)Name the electrode at which reduction happens.[1]

A factory electrolyses concentrated sodium chloride solution (brine) with inert electrodes.

1. (a)Name the three products of this electrolysis.[3]
2. (b)Give one use of any one product.[1]
3. (c)Describe the test that identifies the anode gas.[1]

(Higher) This question compares two acids of the same concentration.

1. (a)Explain what is meant by a strong acid.[2]
2. (b)Acid A has pH 2 and acid B has pH 5, with equal volumes of each. State how many times greater the hydrogen ion concentration of A is, and show how the value follows from the pH values.[2]
3. (c)Equal concentrations of hydrochloric acid and ethanoic acid are reacted separately with magnesium ribbon. Explain which fizzes faster and why.[2]

(Higher) Aqueous copper sulfate is electrolysed with inert carbon electrodes.

1. (a)Write the half equation for the reaction at the cathode.[1]
2. (b)Write the half equation for the reaction at the anode.[1]
3. (c)Explain, in terms of electrons, why the cathode reaction is reduction and the anode reaction is oxidation.[3]
4. (d)Explain why the blue colour of the solution fades during the electrolysis.[1]

(Higher) Explain the key choices and costs of the aluminium extraction cell.

1. (a)Explain why aluminium oxide must be electrolysed rather than reduced with carbon.[2]
2. (b)Explain why cryolite is added to the cell.[2]
3. (c)Explain why the carbon anodes must be replaced regularly.[2]

(Higher) Aqueous zinc bromide is electrolysed with inert electrodes.

1. (a)Name the cathode product and explain the choice.[2]
2. (b)Name the anode product and write its half equation.[2]