1. 1
   A student squeezes juice from a lemon into a test tube and adds a few drops of universal indicator solution, observing a red colour. She then crushes an indigestion tablet, dissolves it in water, adds universal indicator to this solution, and observes a blue colour.

   (a)

   What do the colours observed tell the student about the two solutions?

   [1 mark]

   • AThe lemon juice is acidic (low pH) and the indigestion tablet solution is alkaline (high pH)
   • BThe lemon juice is alkaline (high pH) and the indigestion tablet solution is acidic (low pH)
   • CBoth solutions are neutral, since universal indicator only shows colour in water
   • DThe colours show the temperature of each solution, not its pH

   (b)

   The indigestion tablet contains calcium carbonate, a base. Which type of reaction occurs, and which type of substances form, when the lemon juice (an acid) is added to a solution of the indigestion tablet?

   [1 mark]

   • ACombustion; a salt and hydrogen form
   • BNeutralisation; a salt, water and carbon dioxide form
   • CNeutralisation; only water forms, with no salt
   • DDisplacement; a different acid forms

   (c)

   Describe a simple test, other than tasting the solutions, that the student could carry out to compare the relative acidity of the lemon juice against a very dilute vinegar solution.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A technician prepares a sample of zinc sulfate crystals by adding excess powdered zinc metal to dilute sulfuric acid in a beaker, until no more bubbles of gas are produced and some unreacted zinc remains at the bottom. She then filters the mixture.

   (a)

   Why is excess zinc metal added to the acid, rather than an exact measured amount?

   [1 mark]

   • ATo make the reaction happen faster by increasing the concentration of the acid
   • BTo reduce the mass of zinc sulfate produced
   • CTo ensure all of the acid has reacted, leaving no leftover acid contaminating the salt solution
   • DBecause zinc does not react with dilute sulfuric acid at all

   (b)

   What must the technician do to obtain the zinc sulfate solution from the mixture after the reaction is complete?

   [1 mark]

   • AAdd more zinc to the mixture to react with the zinc sulfate formed
   • BAdd more dilute sulfuric acid until a precipitate forms
   • CEvaporate all the water immediately, without filtering
   • DFilter the mixture to remove the unreacted excess zinc, leaving the zinc sulfate solution

   (c)

   Write the word equation for the reaction between zinc and dilute sulfuric acid, and identify the gas produced.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student is given two oxide powders to test: oxide P dissolves in water to form a solution with a pH of 3, and oxide Q does not dissolve in water but reacts readily with dilute hydrochloric acid to form a colourless salt solution.

   (a)

   Classify oxide P and oxide Q as acidic, basic or amphoteric, giving a reason for each classification based on the information given.

   [3 marks]

   (b)

   Oxide Q is later also found to react with sodium hydroxide solution to form a salt and water. Explain what this additional result shows about oxide Q, and predict, giving a reason, whether oxide Q is more likely to be the oxide of a metal or of a non-metal.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A student prepares a pure, dry sample of potassium nitrate crystals. She uses a titration: she adds a measured volume of dilute potassium hydroxide solution to a conical flask with a few drops of phenolphthalein indicator, then adds dilute nitric acid from a burette until the indicator just changes colour, showing the solution is neutral. She notes the volume of acid needed.

   (a)

   Describe how the student could then obtain pure, dry crystals of potassium nitrate, given that the indicator itself must not be present in the final salt she isolates, and explain the purpose of each step.

   [6 marks]

   (b)

   Explain why a titration method, rather than simply adding excess solid potassium hydroxide to nitric acid, is the appropriate method to prepare potassium nitrate, and explain what would happen if too much nitric acid were accidentally added past the neutralisation point.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A conservator studying weathering of a limestone (calcium carbonate) statue exposed to acid rain places a small chip of the limestone into a test tube of dilute hydrochloric acid to model the reaction. Bubbles of gas form immediately and the chip visibly shrinks in size over several minutes.

   (a)

   Which type of substance is calcium carbonate reacting as in this reaction, and what type of reaction is occurring?

   [1 mark]

   • ACalcium carbonate reacts as a base/carbonate, in a neutralisation-type reaction with the acid
   • BCalcium carbonate reacts as an acid, in a displacement reaction
   • CCalcium carbonate reacts as a metal, in a redox reaction
   • DCalcium carbonate does not react chemically; the shrinking is only physical erosion

   (b)

   Which test could confirm that the gas produced is carbon dioxide?

   [1 mark]

   • AHolding a lit splint at the mouth of the test tube and listening for a squeaky pop
   • BBubbling the gas through limewater and observing whether it turns milky/cloudy
   • CHolding a glowing splint at the mouth of the test tube and observing whether it relights
   • DTesting the gas with damp red litmus paper and observing whether it turns blue

   (c)

   Write the word equation for the reaction between calcium carbonate and hydrochloric acid, naming all the products formed.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A technician prepares a sample of magnesium sulfate crystals. She adds excess powdered magnesium carbonate, an insoluble carbonate, to dilute sulfuric acid in a beaker and stirs until no more bubbles of gas are produced and a small amount of unreacted magnesium carbonate remains undissolved.

   (a)

   Why is excess magnesium carbonate used, rather than an exact measured amount?

   [1 mark]

   • ATo increase the rate of the reaction by increasing the acid concentration
   • BTo reduce the amount of magnesium sulfate produced
   • CTo make sure all the sulfuric acid has fully reacted, so no leftover acid contaminates the salt solution
   • DBecause magnesium carbonate does not react with dilute sulfuric acid

   (b)

   How should the technician remove the unreacted excess magnesium carbonate from the mixture to obtain the magnesium sulfate solution?

   [1 mark]

   • ASimple distillation
   • BChromatography
   • CAdding more dilute sulfuric acid until it dissolves completely
   • DFiltration

   (c)

   Write the word equation for the reaction between magnesium carbonate and dilute sulfuric acid, and name the gas produced.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A technician tests a sample of zinc oxide powder. In test tube 1, she adds the zinc oxide to dilute hydrochloric acid and it dissolves, forming a colourless solution. In test tube 2, she adds a fresh sample of zinc oxide to sodium hydroxide solution and it also dissolves, forming a colourless solution.

   (a)

   State what type of oxide zinc oxide is shown to be by these two results, and explain your reasoning.

   [3 marks]

   (b)

   Write word equations for the reaction of zinc oxide with dilute hydrochloric acid, and for the reaction of zinc oxide with sodium hydroxide solution, naming the salt formed in each case.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A materials scientist compares three oxides formed by elements across the same period: sodium oxide, aluminium oxide and sulfur trioxide. She tests each with dilute hydrochloric acid and with sodium hydroxide solution.

   (a)

   Predict and explain how each of sodium oxide, aluminium oxide and sulfur trioxide would behave when tested with dilute hydrochloric acid and with sodium hydroxide solution, linking your answer to the metallic or non-metallic character of the element forming each oxide.

   [6 marks]

   (b)

   The scientist notices this pattern — basic oxide, then amphoteric oxide, then acidic oxide — matches the change from metallic to non-metallic character seen across a period. Explain what this pattern shows about the general relationship between an element's position in the Periodic Table and the acid-base character of its oxide, and predict, giving a reason, what type of oxide would be formed by an element positioned between sodium and aluminium in the same period.

   [6 marks]

   Total for question 8: 12 marks

End of questions