11.09 Past Paper Practice
Practice Questions
Question 1
(a) Sulfuric acid has many uses.
(i) Define the term acid.
Marking Scheme Answer (1 mark)
- Proton donor [1]
Summary Explanation
An acid is a substance that donates a proton (H⁺) to another species in a chemical reaction. In water, acids release hydrogen ions, H⁺.
(ii) Define the term strong acid.
Marking Scheme Answer (1 mark)
- (An acid that is) completely dissociated in aqueous solution [1]
Summary Explanation
A strong acid fully ionizes in water, meaning virtually all of its acid molecules release their protons (H⁺), leaving no un-ionized acid molecules in solution.
(b) Dilute sulfuric acid is used to make salts known as sulfates.
A method of making zinc sulfate from zinc carbonate involves three steps:
- Step 1: Add an excess of zinc carbonate to 20 cm³ of 0.4 mol/dm³ dilute sulfuric acid until the reaction is complete.
- Step 2: Filter the mixture.
- Step 3: Heat the filtrate until a saturated solution forms and then allow it to crystallize.
(i) Suggest two observations which show that the reaction is complete in Step 1.
Marking Scheme Answer (2 marks)
- No more fizzing [1]
- (Zinc carbonate) stops dissolving / a (white) solid remains [1]
Summary Explanation
During the reaction of zinc carbonate with sulfuric acid, carbon dioxide is released (fizzing). Once no more bubbles are produced and some solid is left undissolved, it indicates all the acid is used up.
(ii) State the colour of methyl orange in aqueous sodium hydroxide.
Marking Scheme Answer (1 mark)
- Yellow [1]
Summary Explanation
Methyl orange changes color in different pH conditions. In basic (alkaline) solutions like sodium hydroxide, it turns yellow.
Question 2
(a) Solid sodium hydroxide is a base that dissolves to form an aqueous solution, NaOH(aq).
State what is meant by the term base.
Marking Scheme Answer (1 mark)
- Proton acceptor [1]
Summary Explanation
Bases are substances that accept protons (H⁺). When a base dissolves in water, it can accept H⁺ from water molecules or from acids.
(b) State the term given to a base which dissolves to form an aqueous solution.
Marking Scheme Answer (1 mark)
- Alkali [1]
Summary Explanation
An alkali is simply a base that is water-soluble, producing hydroxide ions (OH⁻) in solution.
(c) State the colour of thymolphthalein in NaOH(aq).
Marking Scheme Answer (1 mark)
- Blue [1]
Summary Explanation
Thymolphthalein is an acid-base indicator that appears blue in alkaline solutions.
(d) Complete the word equation for the reaction of NaOH(aq) with ammonium chloride.
Marking Scheme Answer (3 marks)
Products:
- Sodium chloride [1]
- Water [1]
- Ammonia [1]
Summary Explanation
When an alkali (NaOH) reacts with ammonium salts (e.g., NH₄Cl), ammonia gas, water, and a salt (NaCl) are formed.
(e) Some metal oxides react with NaOH(aq).
(i) State the term given to metal oxides which react with bases such as NaOH(aq).
Marking Scheme Answer (1 mark)
- Amphoteric (oxides) [1]
Summary Explanation
Amphoteric oxides react with both acids and bases. Aluminum oxide and zinc oxide are classic examples.
(ii) Name a metal oxide which reacts with NaOH(aq).
Marking Scheme Answer (1 mark)
- Aluminium oxide OR Zinc oxide [1]
Summary Explanation
Al₂O₃ and ZnO both show amphoteric behavior, reacting with acids to form salts and with bases to form complex ions or salts.
(f) Ethanoic acid, CH₃COOH, is a weak acid.
(ii) Suggest the pH of dilute ethanoic acid.
Marking Scheme Answer (1 mark)
- 3 ≤ pH < 7 [1]
Summary Explanation
Weak acids partially dissociate, typically having a pH in the acidic range but higher (less acidic) than strong acids of similar concentration.
(iii) Complete the symbol equation to show the dissociation of ethanoic acid.
Marking Scheme Answer (3 marks)CH3COOH⇌CH3COO−+H+
- M1: H⁺ [1]
- M2: CH₃COO⁻ [1]
- M3: Use of ⇌ [1]
Summary Explanation
A weak acid like ethanoic acid sets up an equilibrium: a portion of molecules release H⁺, while others remain undissociated.
(iv) Write the ionic equation for the reaction when an acid neutralizes a soluble base.
Marking Scheme Answer (1 mark)H++OH− → H2O
Summary Explanation
Neutralization is fundamentally a reaction between hydrogen ions (from an acid) and hydroxide ions (from a base) to form water.
Question 3
Sodium reacts with cold water to form hydrogen gas and a solution of a strong alkali.
(i) State the test for hydrogen gas.
Marking Scheme Answer (1 mark)
- Test: Apply a lit splint [½ mark]
- Positive result: A ‘pop’ sound [½ mark]
Summary Explanation
When hydrogen gas is ignited with a lit splint, it produces a characteristic ‘squeaky pop’ due to rapid combustion of H₂.
(ii) Suggest the pH of a solution of a strong alkali.
Marking Scheme Answer (1 mark)
- pH = 13–14 [1]
Summary Explanation
Strong alkalis (e.g., NaOH) typically have very high pH values, close to 14, indicating high [OH⁻] in solution.
(iii) Name a substance which can be used to confirm the pH of a solution of a strong alkali.
Marking Scheme Answer (1 mark)
- Universal indicator [1]
Summary Explanation
Universal indicator changes color through a full pH range, showing purple in strongly alkaline solutions.
(iv) Write the symbol equation for the reaction between sodium and cold water. Include state symbols.
Marking Scheme Answer (3 marks)2 Na(s)+2 H2O(l) → 2 NaOH(aq)+H2(g)
- M1: Correct reactants/products [1]
- M2: Correct balancing [1]
- M3: State symbols [1]
Summary Explanation
Alkali metals like sodium react vigorously with water, releasing hydrogen gas and forming sodium hydroxide solution.
Question 4
When potassium is added to water, it reacts vigorously, and a coloured flame is seen.
(i) State the colour of the flame seen.
Marking Scheme Answer (1 mark)
- Lilac [1]
Summary Explanation
Potassium burns with a characteristic lilac/purple flame when it reacts with water or is heated strongly in air
.
(ii) The solution formed is potassium hydroxide, a strong alkali.
State the formula of the ion responsible for alkalinity in a solution.
Marking Scheme Answer (1 mark)
- OH⁻ [1]
Summary Explanation
All alkaline solutions contain hydroxide ions (OH⁻), which are responsible for their basic properties.
(iii) State the colour of litmus in a strong alkali.
Marking Scheme Answer (1 mark)
- Blue [1]
Summary Explanation
Litmus turns blue in alkaline solutions (pH > 7), indicating the presence of OH⁻ ions.
Aqueous potassium hydroxide reacts with a dilute acid to produce aqueous potassium chloride, KCl(aq), which is a salt.
(i) Name the dilute acid used.
Marking Scheme Answer (1 mark)
- Hydrochloric (acid) [1]
Summary Explanation
Neutralizing potassium hydroxide with hydrochloric acid forms potassium chloride (KCl) and water.
(ii) State the type of reaction taking place.
Marking Scheme Answer (1 mark)
- Neutralisation [1]
Summary Explanation
An acid plus a base reacts to form a salt and water, which is a classic neutralization reaction.
(iii) Name the experimental technique used when salts are made by reacting a dilute acid with an aqueous alkali.
Marking Scheme Answer (1 mark)
- Titration [1]
Summary Explanation
Titration allows precise addition of acid to the alkali (or vice versa) until the neutralization endpoint is reached, forming a pure salt solution.
When aqueous silver nitrate, AgNO₃(aq), is added to aqueous potassium chloride, a precipitate is formed.
(i) State the colour of the precipitate formed.
Marking Scheme Answer (1 mark)
- White [1]
Summary Explanation
Silver chloride (AgCl) forms a white precipitate. Many silver halides are sparingly soluble, so they precipitate out of solution.
(ii) Name the precipitate formed.
Marking Scheme Answer (1 mark)
- Silver chloride [1]
Summary Explanation
Silver chloride is insoluble in water and appears as a white solid.
(iii) Write the ionic equation for the reaction. Include state symbols.
Marking Scheme Answer (3 marks)Ag+(aq)+Cl−(aq) → AgCl(s)
- M1: AgCl (as only product) [1]
- M2: Ag⁺ and Cl⁻ (as only reactants) [1]
- M3: State symbols [1]
Summary Explanation
In precipitation reactions, only the ions directly involved in forming the insoluble product are included in the ionic equation.
Question 5
Sodium reacts vigorously with water to form aqueous sodium hydroxide, NaOH, which is a strong base.
(i) Explain in terms of proton transfer what is meant by a base.
Marking Scheme Answer (1 mark)
- Proton acceptor [1]
Summary Explanation
A base takes up protons (H⁺) from an acid or from water molecules, thereby increasing the pH of the solution.
(ii) State a pH number that indicates the presence of a strong alkali.
Marking Scheme Answer (1 mark)
- pH 14 [1]
Summary Explanation
A pH of 14 is typical of a very strong alkali in standard aqueous solutions.
(iii) State the colour of methyl orange in aqueous sodium hydroxide.
Marking Scheme Answer (1 mark)
- Yellow [1]
Summary Explanation
In strongly alkaline solutions, methyl orange appears yellow.
When NaOH(aq) is added to aqueous iron(III) chloride, FeCl₃(aq), a solid product is formed.
(i) Name the type of reaction where a solid is formed from two solutions.
Marking Scheme Answer (1 mark)
- Precipitation [1]
Summary Explanation
When two aqueous solutions react to form an insoluble product, it is called a precipitation reaction.
(ii) State the colour of this solid product.
Marking Scheme Answer (1 mark)
- Red-brown [1]
Summary Explanation
Iron(III) hydroxide typically appears as a brownish or red-brown precipitate.
(iii) Name this solid product.
Marking Scheme Answer (1 mark)
- Iron(III) hydroxide [1]
Summary Explanation
Fe3+ ions react with OH− ions to form Fe(OH)3, an insoluble solid.
(iv) Write the ionic equation for the reaction. Include state symbols.
Marking Scheme Answer (3 marks)Fe3+(aq)+3 OH−(aq) → Fe(OH)3(s)
- M1: Fe(OH)₃ as the only product [1]
- M2: Fe³⁺ and OH⁻ as the only reactants [1]
- M3: Correct state symbols [1]
Summary Explanation
This precipitation results from the insoluble iron(III) hydroxide forming when Fe³⁺ and OH⁻ combine in solution.
Question 6
Aluminium is more reactive than copper.
When aluminium is added to aqueous copper(II) sulfate, no immediate reaction is seen.
Explain why.
Marking Scheme Answer (1 mark)
- Unreactive coating of aluminium oxide [1]
Summary Explanation
Aluminium naturally forms a thin oxide layer that protects the metal from reacting until it is removed or disrupted.
Aluminium reacts with oxygen to form an amphoteric oxide.
(i) State what is meant by the term amphoteric.
Marking Scheme Answer (1 mark)
- Neutralises both acids and alkalis [1]
Summary Explanation
An amphoteric substance can behave as an acid or a base, reacting with both strong acids and strong bases.
(ii) The reaction between aluminium oxide and aqueous sodium hydroxide forms a salt containing the negative ion AlO₂⁻. The only other product is water.
Write a chemical equation for the reaction between aluminium oxide and aqueous sodium hydroxide.
Marking Scheme Answer (2 marks)2 NaOH+Al2O3 → 2 NaAlO2+H2O
- M1: NaAlO₂ on the right-hand side [1]
- M2: Equation fully correct [1]
Summary Explanation
Aluminium oxide dissolves in strong bases to form sodium aluminate (NaAlO2) and water, showing its amphoteric nature.
Question 7
Calcium hydroxide, Ca(OH)₂, is slightly soluble in water.
(a) Calcium hydroxide can be made by the reaction of calcium with water.
(i) Write the chemical equation for this reaction.
Marking Scheme Answer (2 marks)Ca+2 H2O → Ca(OH)2+H2
- M1: H₂ as a product [1]
- M2: Fully correct equation [1]
Summary Explanation
Calcium is less reactive than alkali metals but still reacts with water to form calcium hydroxide and hydrogen gas.
(ii) Name another substance that reacts with water to form calcium hydroxide.
Marking Scheme Answer (1 mark)
- Calcium oxide [1]
Summary Explanation
Calcium oxide (quicklime) reacts with water in an exothermic process called “slaking,” producing calcium hydroxide (slaked lime).
(b) When calcium hydroxide dissolves in water, it dissociates into ions and forms a weakly alkaline solution.
(i) Suggest the pH of aqueous calcium hydroxide.
Marking Scheme Answer (1 mark)
- 7 < pH < 12 [1]
Summary Explanation
Because Ca(OH)₂ is only slightly soluble, it forms a mildly alkaline solution rather than a very high pH solution.
(ii) Give the formula of the ion responsible for making the solution alkaline.
Marking Scheme Answer (1 mark)
- OH⁻ [1]
Summary Explanation
Hydroxide ions (OH⁻) increase the pH of a solution, making it alkaline.
Question 8
Acids are important laboratory chemicals.
(a) Some acids completely dissociate in water to form ions.
(i) State the term applied to acids that completely dissociate in water.
Marking Scheme Answer (1 mark)
- Strong [1]
Summary Explanation
Strong acids ionize fully in water, releasing a high concentration of H⁺ ions.
(ii) Complete the equation to show the complete dissociation of sulfuric acid in water.
Marking Scheme Answer (2 marks)H2SO4 → 2 H++SO42−
- M1: H⁺ [1]
- M2: Correct equation [1]
Summary Explanation
Sulfuric acid (H₂SO₄) yields two protons per molecule, making it a diprotic strong acid.
(iii) State the colour of methyl orange in sulfuric acid.
Marking Scheme Answer (1 mark)
- Pink/Red [1]
Summary Explanation
Methyl orange is red (or sometimes described as pink) in acidic solutions.
(b) The equation for the reaction between powdered zinc carbonate and dilute nitric acid is shown:
ZnCO3 + 2 HNO3 → Zn(NO3)2 + H2O + CO2
(i) Complete the equation by adding state symbols.
Marking Scheme Answer (2 marks)ZnCO3(s)+2 HNO3(aq) → Zn(NO3)2(aq)+H2O(ℓ)+CO2(g)
- Reactant states [1]
- Product states [1]
Summary Explanation
Zinc carbonate is a solid, nitric acid is aqueous, zinc nitrate is soluble (aqueous), water is liquid, and carbon dioxide is a gas.
Question 9
Ammonia is a base which forms a weakly alkaline solution when dissolved in water.
(i) Define the term base.
Marking Scheme Answer (1 mark)
- Proton acceptor [1]
Summary Explanation
Ammonia (NH₃) accepts protons from water, forming NH₄⁺ and OH⁻, which slightly raises the solution’s pH.
(ii) Suggest the pH of aqueous ammonia.
Marking Scheme Answer (1 mark)
- 7 < x ≤ 11 [1]
Summary Explanation
Because ammonia is a weak base, it partially ionizes, giving a pH typically in the mildly to moderately alkaline range.
Question 10
When Group I metals are added to water, they fizz, and an alkaline solution forms.
(i) Name the gas given off.
Marking Scheme Answer (1 mark)
- Hydrogen [1]
Summary Explanation
All Group I metals (e.g., Na, K) release hydrogen gas upon contact with water.
(ii) Identify the ion present in the solution which makes the solution alkaline.
Marking Scheme Answer (1 mark)
- Hydroxide / OH⁻ [1]
Summary Explanation
The reaction forms metal hydroxides, creating OH⁻ ions in solution.
(iii) Write the chemical equation for the reaction between sodium and water.
Marking Scheme Answer (2 marks)2 Na+2 H2O → 2 NaOH+H2
- M1: NaOH (as a product) [1]
- M2: Rest of equation correct [1]
Summary Explanation
Similar to Question 3(iv), this shows sodium reacting vigorously with water to form sodium hydroxide and hydrogen gas.
Question 11
This question is about reactions of bases and acids.
(a) Ammonia is a gas at room temperature.
What is the test for ammonia gas? Describe the positive result of this test.
Marking Scheme Answer (2 marks)
- Test: (Damp) litmus [1]
- Result: (Turns) blue [1]
Summary Explanation
Ammonia is alkaline, so moist red litmus paper turns blue in its presence.
(b) Ammonia reacts with water to form ions.
(i) How does this equation show that ammonia, NH₃, behaves as a base?
Marking Scheme Answer (1 mark)
- Proton acceptor [1]
Summary Explanation
NH₃ accepts H⁺ (from H₂O), generating NH₄⁺ (ammonium).
(ii) Aqueous ammonia is described as a weak base. Suggest the pH of aqueous ammonia.
Marking Scheme Answer (1 mark)
- Above pH 7 up to 11 [1]
Summary Explanation
Being only partially ionized, ammonia solutions have a moderate pH in the alkaline region.
(iii) Describe what is seen when aqueous ammonia is added to aqueous copper(II) sulfate, until no further change is seen.
Marking Scheme Answer (3 marks)
- Blue precipitate [1]
- Precipitate dissolves [1]
- Deep blue solution remains [1]
Summary Explanation
A pale blue precipitate of copper(II) hydroxide initially forms, which then dissolves in excess ammonia to form a deep blue complex ion [Cu(NH3)4]2+
(c) Aqueous sodium hydroxide, NaOH(aq), is a strong alkali that reacts with dilute sulfuric acid exothermically.
(i) What type of reaction is this?
Marking Scheme Answer (1 mark)
- Neutralisation [1]
Summary Explanation
Mixing a strong acid (H₂SO₄) with a strong base (NaOH) produces salt and water, releasing heat.
(ii) Complete the equation for the reaction between aqueous sodium hydroxide and dilute sulfuric acid.
Marking Scheme Answer (2 marks)2 NaOH+H2SO4 → Na2SO4+2 H2O2
- Na₂SO₄ [1]
- 2H₂O [1]
Summary Explanation
Balancing requires two moles of NaOH for every mole of H₂SO₄ to fully neutralize the acid, forming sodium sulfate and water.
Question 12
Some acids are described as weak acids.
State the meaning of the term weak acid.
Marking Scheme Answer (2 marks)
- Donate or lose protons [1]
- Does not fully ionize / partially ionizes / forms an equilibrium mixture [1]
Summary Explanation
A weak acid only partially releases H⁺ ions in solution, setting up an equilibrium between the un-ionized acid and its ions.
Question 13
Zinc oxide is amphoteric.
Describe two simple experiments to show that zinc oxide is amphoteric. Name the reagents you would use and describe the observations you would make.
Marking Scheme Answer (3 marks)
- Reagent 1: Add a named acid (e.g., HCl) [1]
- Observation: Zinc oxide dissolves/disappears in acid [1]
- Reagent 2: Add a named alkali (e.g., NaOH) [1]
- Observation: Zinc oxide dissolves/disappears in alkali [1]
Summary Explanation
Amphoteric oxides react both with strong acids and with strong bases. Zinc oxide, for example, dissolves in dilute HCl to form zinc chloride and also dissolves in strong alkali to form zincates.
Question 14
Ethanoic acid is a weak acid, and hydrochloric acid is a strong acid. Both dissociate in aqueous solution.
(a) (i) Define the term acid.
Marking Scheme Answer (1 mark)
- Proton donor [1]
Summary Explanation
Acids donate H⁺ ions when dissolved in water or when reacting with bases.
(ii) The chemical equation shows the changes when the strong acid, hydrochloric acid, is added to water.
Complete the chemical equation to show the changes which occur when the weak acid, ethanoic acid, is added to water.
Marking Scheme Answer (2 marks)CH3COOH⇌CH3COO−+H+
- M1: CH₃COO⁻ [1]
- M2: Correct use of ⇌ [1]
Summary Explanation
Unlike HCl, which fully ionizes, ethanoic acid partially ionizes, so the equilibrium arrow (⇌) is used instead of a single arrow.
(b) A student does experiments to show that hydrochloric acid is a strong acid and ethanoic acid is a weak acid. Both acids are added to separate samples of lumps of calcium carbonate.
(i) State two observations which would show that hydrochloric acid is a stronger acid than ethanoic acid.
Marking Scheme Answer (2 marks)
Any two from:
- Faster rate of fizzing [1]
- Solid dissolves quicker [1]
- Fizzing stops quicker [1]
- Dissolving stops quicker [1]
Summary Explanation
Stronger acids release more H⁺ ions rapidly, causing faster reaction rates with calcium carbonate (more vigorous fizzing).
(ii) The student uses the same size container and ensures the same pressure for each experiment. State three other conditions which must be kept the same to ensure fair testing.
Marking Scheme Answer (3 marks)
Any three from:
- Temperature [1]
- Volume of acid [1]
- Concentration of acid [1]
- Mass/amount of CaCO₃ [1]
- Particle size/surface area of CaCO₃ [1]
Summary Explanation
Experimental control requires consistent conditions except for the variable being tested (type of acid). This ensures that any difference in reaction rate is due only to acid strength.
Question 15
Phosphorus(V) oxide, P₄O₁₀, is an acidic oxide.
It reacts with aqueous sodium hydroxide to form a salt containing the phosphate ion, PO₄³⁻. Water is the only other product.
Write a chemical equation for the reaction between phosphorus(V) oxide and aqueous sodium hydroxide.
Marking Scheme Answer (2 marks)P4O10+12 NaOH → 4 Na3PO4+6 H2O
- M1: Na₃PO₄ [1]
- M2: Equation completely correct [1]
Summary Explanation
P₄O₁₀ is an acidic oxide and reacts with a strong base (NaOH) to form sodium phosphate and water.
Question 16
Some airbags contain silicon(IV) oxide. When the airbag is used, sodium oxide is formed.
Oxides can be classified as acidic, amphoteric, basic, or neutral.
Classify each of these oxides:
- Sodium oxide
- Silicon(IV) oxide
Marking Scheme Answer (2 marks)
- Sodium oxide – Basic [1]
- Silicon dioxide – Acidic [1]
Summary Explanation
Metal oxides like Na₂O are typically basic, while many non-metal oxides (e.g., SiO₂) are acidic oxides.
Question 17
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.
(i) Name gas P.
Marking Scheme Answer (1 mark)
- Hydrogen [1]
Summary Explanation
Calcium reacting with water releases hydrogen gas (the pop test confirms H₂).
(ii) Identify the ion responsible for making solution Q alkaline.
Marking Scheme Answer (1 mark)
- Hydroxide or OH⁻ [1]
Summary Explanation
Calcium hydroxide slightly dissolves to form OH⁻ ions, raising the pH of the solution.
(iii) Suggest the pH of solution Q.
Marking Scheme Answer (1 mark)
- 7 < pH ≤ 12 [1]
Summary Explanation
Because Ca(OH)₂ is only sparingly soluble, the solution is weakly alkaline, usually in the 8–12 range.
(iv) Write a chemical equation for the reaction of calcium with cold water.
Marking Scheme Answer (2 marks)Ca+2 H2O → Ca(OH)2+H2
- M1: Ca(OH)₂ [1]
- M2: Rest of equation [1]
Summary Explanation
Similar to other Group II metals, calcium forms hydroxide and hydrogen gas upon reacting with water.
Question 18: Reactions of Dilute Sulfuric Acid
(i) Reaction with Magnesium Hydroxide
Mg(OH)2+H2SO4 → MgSO4+2 H2O
Mark Scheme
- M1: Correct formula of both Mg(OH)₂ and MgSO₄
- M2: Fully correct equation
Summary Explanation
Magnesium hydroxide neutralizes sulfuric acid to give magnesium sulfate and water.
(ii) Reaction with Zinc
Zn+H2SO4 → ZnSO4+H2
Mark Scheme
- M1: Correct formula of ZnSO₄
- M2: Fully correct equation
Summary Explanation
Zinc displaces hydrogen from sulfuric acid, forming zinc sulfate and hydrogen gas.
(iii) Reaction with Sodium Carbonate
Na2CO3 + H2SO4 → Na2SO4 + H2O + CO2
Mark Scheme
- M1: Correct formulae of both Na₂CO₃ and Na₂SO₄
- M2: Fully correct equation
Summary Explanation
Acids react with carbonates to form a salt, water, and carbon dioxide gas (the fizzing indicates CO₂ release).