The characteristic properties of acids and bases
7.1What the syllabus asks of you
- State that aqueous solutions of acids contain H+ ions and aqueous solutions of alkalis contain OH– ions
- Define acids as proton donors and bases as proton acceptors
- State that bases are oxides or hydroxides of metals and that alkalis are soluble bases
- Describe the characteristic properties of acids in terms of their reactions with: (a) metals (b) bases (c) carbonates
- Describe the characteristic properties of bases in terms of their reactions with: (a) acids (b) ammonium salts
- State that a neutralisation reaction occurs between an acid and a base
- Describe the neutralisation reaction between an acid and an alkali to produce water, H+(aq) + OH−(aq) → H2O(l )
- Describe acids and alkalis in terms of their effects on: (a) litmus (b) thymolphthalein (c) methyl orange
- Define a strong acid as an acid that is completely dissociated in aqueous solution and a weak acid as an acid that is partially dissociated in aqueous solution
- State examples of strong acids, including hydrochloric acid, nitric acid and sulfuric acid and construct the symbol equations to show their complete dissociation, e.g. HCl(aq) → H+(aq) + Cl –(aq)
- State examples of weak acids, including carboxylic acids and construct the symbol equations to show their partial dissociation, e.g. for ethanoic acid, CH3COOH(aq) ⇌ H+(aq) + CH3COO–(aq)
- Describe how to compare hydrogen ion concentration, neutrality, relative acidity and relative alkalinity in terms of colour and pH using universal indicator paper
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Chapter 7: The characteristic properties of acids and bases
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55 questions
1May / June 2026 · Paper 11 · Q18Show mark scheme →
Aneither a base nor an alkali | a base and an alkali
Bneither a base nor an alkali | an alkali but not a base
Ca base but not an alkali | a base and an alkali
Da base but not an alkali | an alkali but not a base
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2May / June 2026 · Paper 11 · Q19Show mark scheme →
ACH3CH2COO+
BCH3CH2CH2COO–
CH+
DH–
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3May / June 2026 · Paper 12 · Q18Show mark scheme →
AMagnesium reacts with solution P to form a salt, but does not form a salt with solution Q.
BMore particles are dissociated in solution P than are dissociated in solution Q.
CSolution Q contains a stronger acid than solution P.
DThe particles are closer together in solution Q than they are in solution P.
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4Oct / Nov 2025 · Paper 11 · Q17Show mark scheme →
AEthanoic acid is a weak acid because when it is added to excess alkali not all of the ethanoic acid reacts.
BEthanoic acid is a weaker acid than sulfuric acid because a smaller proportion of its molecules dissociate in aqueous solution.
CHydrochloric acid is a stronger acid than ethanoic acid because hydrochloric acid always has a higher pH than ethanoic acid.
DSulfuric acid is a strong acid because it produces two hydrogen ions for every molecule that dissociates.
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5Oct / Nov 2025 · Paper 12 · Q19Also set in Oct / Nov 2021 Paper 11Show mark scheme →
Aatoms → molecules
Bions → molecules
Catoms → ions
Dions → atoms
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6May / June 2025 · Paper 11 · Q20Show mark scheme →
A3–4, increases
B3–4, decreases
C8–9, increases
D8–9, decreases
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7May / June 2025 · Paper 12 · Q20Show mark scheme →
Amethyl orange test: red; thymolphthalein test: colourless
Bmethyl orange test: yellow; thymolphthalein test: colourless
Cmethyl orange test: red; thymolphthalein test: blue
Dmethyl orange test: yellow; thymolphthalein test: blue
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8May / June 2025 · Paper 12 · Q21Show mark scheme →
Amethanoic acid: HCOOH(aq) → H⁺(aq) + HCOO⁻(aq); nitric acid: HNO₃(aq) → H⁺(aq) + NO₃⁻(aq)
Bmethanoic acid: HCOOH(aq) → H⁺(aq) + HCOO⁻(aq); nitric acid: HNO₃(aq) ⇌ H⁺(aq) + NO₃⁻(aq)
Cmethanoic acid: HCOOH(aq) ⇌ H⁺(aq) + HCOO⁻(aq); nitric acid: HNO₃(aq) ⇌ H⁺(aq) + NO₃⁻(aq)
Dmethanoic acid: HCOOH(aq) ⇌ H⁺(aq) + HCOO⁻(aq); nitric acid: HNO₃(aq) → H⁺(aq) + NO₃⁻(aq)
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9Oct / Nov 2024 · Paper 12 · Q21Show mark scheme →
Acarbon
Bcopper
Cmagnesium oxide
Dsodium carbonate
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10Oct / Nov 2024 · Paper 12 · Q22Show mark scheme →
Ahydrochloric acid
Bsodium chloride
Csodium hydroxide
Dsulfuric acid
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11May / June 2024 · Paper 11 · Q23Show mark scheme →
Agreater than 7, H+
Bgreater than 7, OH–
Cless than 7, H+
Dless than 7, OH–
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12May / June 2024 · Paper 11 · Q24Show mark scheme →
Acalcium carbonate
Bphosphoric acid
Cpotassium hydroxide
Dsodium nitrate
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13May / June 2024 · Paper 12 · Q21Show mark scheme →
Acalcium hydroxide
Bethanoic acid
Cnitric acid
Dsodium hydroxide
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14May / June 2024 · Paper 12 · Q22Show mark scheme →
ASome molecules are not dissociated.
BWeak acids do not react with carbonates.
CWeak acids always form more dilute solutions than strong acids.
DWeak acids always have lower pH values than strong acids.
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15Oct / Nov 2023 · Paper 11 · Q20Show mark scheme →
AIt has a pH below 7.
BIt gives a blue-green colour in the flame test.
CIt reacts with ammonia to form an ammonium salt.
DIt turns yellow when methyl orange is added.
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16Oct / Nov 2023 · Paper 12 · Q19Show mark scheme →
AA base will react with an ammonium salt to produce a gas that turns damp blue litmus paper red.
BAdding a base to an acidic solution will increase the pH of the solution.
CAqueous sodium hydroxide is an alkali but not a base.
DIn a neutralisation reaction, a base donates a proton to an acid.
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17May / June 2023 · Paper 11 · Q16Show mark scheme →
ApH decreases; colour of solution shifts towards colour X
BpH decreases; colour of solution shifts towards colour Y
CpH increases; colour of solution shifts towards colour X
DpH increases; colour of solution shifts towards colour Y
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18May / June 2023 · Paper 11 · Q19Show mark scheme →
AHCl(aq) is a weak acid and HNO3(aq) is a strong acid.
BHNO3(aq) has a lower formula mass than HCl(aq).
CThe HNO3(aq) is more concentrated than the HCl(aq).
DThe HCl(aq) has dissociated more than the HNO3(aq).
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19May / June 2023 · Paper 11 · Q20Show mark scheme →
Aaqueous sodium carbonate and dilute sulfuric acid
Baqueous sodium chloride and aqueous silver nitrate
Caqueous sodium hydroxide and dilute ethanoic acid
Dzinc and dilute hydrochloric acid
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20May / June 2023 · Paper 12 · Q21Show mark scheme →
AAn aqueous solution of X will not conduct electricity.
BAtoms of a metallic element are present in X.
CAtoms of hydrogen are present in X.
DX is ionically bonded.
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21May / June 2023 · Paper 12 · Q22Show mark scheme →
AHydrochloric acid reacts with magnesium carbonate to form three different products.
BHydrochloric acid reacts with magnesium to form magnesium chloride and water.
CWhen hydrochloric acid is added to a colourless solution of thymolphthalein, it turns blue.
DWhen hydrochloric acid is warmed with ammonium chloride, ammonia is formed.
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22May / June 2023 · Paper 12 · Q23Show mark scheme →
A1 and 2
B1 and 4
C2 and 3
D3 and 4
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23Oct / Nov 2022 · Paper 12 · Q27Show mark scheme →
AP is alkaline.
BQ has the lowest concentration of hydrogen ions.
CR can neutralise excess stomach acid.
DS has a pH value closest to neutral.
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24Oct / Nov 2022 · Paper 12 · Q28Show mark scheme →
Aaqueous sodium hydroxide / ammonia
Baqueous sodium hydroxide / carbon dioxide
Cdilute hydrochloric acid / ammonia
Ddilute hydrochloric acid / carbon dioxide
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25May / June 2022 · Paper 11 · Q13Show mark scheme →
ACa+ + OH– + H+ + NO3– → CaNO3 + H2O
BCa(OH)2 + 2HNO3 → Ca(NO3)2 + H2O
CCa2+(OH–)2 + 2H+NO3– → Ca2+(NO3–)2 + H2O
DOH– + H+ → H2O
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26May / June 2022 · Paper 11 · Q25Show mark scheme →
AAll strong acids react with carbonates but all weak acids do not.
BThe oxides of Group I metals are amphoteric.
CThe pH of 1.0 mol/dm³ ethanoic acid, CH₃COOH, is higher than the pH of 1.0 mol/dm³ sulfuric acid, H₂SO₄.
DThe pH of 1.0 mol/dm³ nitric acid, HNO₃, is lower than the pH of 1.0 mol/dm³ hydrochloric acid, HCl.
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27May / June 2022 · Paper 12 · Q25Show mark scheme →
A1, 2 and 3
B1 and 3 only
C1 only
D2 and 3 only
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28May / June 2022 · Paper 12 · Q26Show mark scheme →
Ahydrochloric | sulfuric | ethanoic
Bhydrochloric | nitric | ethanoic
Cnitric | sulfuric | hydrochloric
Dsulfuric | hydrochloric | nitric
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29Oct / Nov 2021 · Paper 11 · Q22Show mark scheme →
AMagnesium reacts with solution P to form a salt, but does not form a salt with solution Q.
BMore particles are dissociated in solution P than are dissociated in solution Q.
CSolution Q contains a stronger acid than solution P.
DThe particles are closer together in solution Q than they are in solution P.
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30Oct / Nov 2021 · Paper 12 · Q22Show mark scheme →
AA 0.1 mol / dm3 solution of ethanoic acid has a higher pH than a 0.1 mol / dm3 solution of hydrochloric acid.
BAll bases dissolve in water to produce OH– ions.
CBases react with nitrates to produce ammonia.
DOxides of metals are always acidic in character.
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31May / June 2021 · Paper 11 · Q23Show mark scheme →
Acalcium carbonate
Bphosphoric acid
Cpotassium hydroxide
Dsodium nitrate
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32May / June 2021 · Paper 12 · Q22Also set in May / June 2021 Paper 11, Oct / Nov 2016 Paper 11Show mark scheme →
ANH3 1, HCl 7, NaCl 13, NaOH 11
BNH3 7, HCl 1, NaCl 11, NaOH 13
CNH3 11, HCl 1, NaCl 7, NaOH 13
DNH3 13, HCl 11, NaCl 7, NaOH 1
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33May / June 2021 · Paper 12 · Q24Show mark scheme →
Acombustion
Bneutralisation
Coxidation
Dprecipitation
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34May / June 2020 · Paper 11 · Q22Show mark scheme →
AIt is manufactured by heating hydrogen, oxygen and sulfur together.
BIt is used as a battery acid.
CIt is used as a detergent.
DIt is used to neutralise alkaline soils.
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35May / June 2020 · Paper 12 · Q20Show mark scheme →
Ahigher / higher
Bhigher / lower
Clower / higher
Dlower / lower
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36May / June 2020 · Paper 12 · Q21Also set in May / June 2020 Paper 11Show mark scheme →
Acalcium nitrate
Bpotassium hydroxide
Csodium chloride
Dsulfuric acid
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37Oct / Nov 2019 · Paper 11 · Q18Show mark scheme →
ASodium hydroxide is an acid and reacts with an alkali to form water as a product.
BSodium hydroxide will lower the pH of the solution.
CThe pH of the neutral solution is 14.
DThe pH of the solution before sodium hydroxide is added is below 7.
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38Oct / Nov 2019 · Paper 11 · Q19Show mark scheme →
Ablue (weak alkali)
Bgreen (neutral)
Cpurple (strong alkali)
Dred (acidic)
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39Oct / Nov 2019 · Paper 12 · Q18Show mark scheme →
AIt contains more OH– ions than H+ ions.
BIt has pH 9.
CIts reaction with calcium carbonate produces hydrogen.
DIt reacts with aqueous ammonia.
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40May / June 2019 · Paper 12 · Q21Also set in May / June 2019 Paper 11Show mark scheme →
AIt is an organic acid.
BIt is a poor conductor of electricity.
CIt is only slightly dissociated in water.
DIt reacts only with very reactive metals.
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41Oct / Nov 2018 · Paper 11 · Q23Show mark scheme →
Aas a bleach
Bas a food preservative
Cin the manufacture of detergents
Din the manufacture of vanadium(V) oxide, V2O5
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42Oct / Nov 2018 · Paper 12 · Q20Also set in Oct / Nov 2018 Paper 11Show mark scheme →
ANaOH(aq) and NH4Cl(s): ✓; H2SO4(aq) and NH4Cl(s): ✓; H2SO4(aq) and Mg(s): ✗
BNaOH(aq) and NH4Cl(s): ✓; H2SO4(aq) and NH4Cl(s): ✗; H2SO4(aq) and Mg(s): ✓
CNaOH(aq) and NH4Cl(s): ✗; H2SO4(aq) and NH4Cl(s): ✓; H2SO4(aq) and Mg(s): ✗
DNaOH(aq) and NH4Cl(s): ✗; H2SO4(aq) and NH4Cl(s): ✗; H2SO4(aq) and Mg(s): ✓
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43May / June 2018 · Paper 11 · Q22Show mark scheme →
Aa strong acid
Ba strong base
Ca weak acid
Da weak base
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44Oct / Nov 2017 · Paper 11 · Q26Show mark scheme →
A1, 2 and 3
B1 and 2 only
C1 and 3 only
D2 and 3 only
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45Oct / Nov 2017 · Paper 12 · Q23Show mark scheme →
ApH 2
BpH 7
CpH 10
DpH 14
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46Oct / Nov 2017 · Paper 12 · Q24Show mark scheme →
ACu ✓, CuO ✓, CuCO3 ✓
BCu ✗, CuO ✓, CuCO3 ✗
CCu ✓, CuO ✗, CuCO3 ✓
DCu ✗, CuO ✓, CuCO3 ✓
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47Oct / Nov 2017 · Paper 12 · Q25Show mark scheme →
ANa+, Cl–, H+ and OH–
BNa+, Cl– and H+ only
CNa+ and Cl– only
DH+ and OH– only
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48May / June 2017 · Paper 11 · Q21Show mark scheme →
Aas a bleach.
Bin food preservation.
Cin the manufacture of detergents.
Din the purification of drinking water.
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49May / June 2017 · Paper 11 · Q22Show mark scheme →
Astrong acids, weak acids, weak bases, strong bases
Bstrong bases, weak bases, weak acids, strong acids
Cweak acids, strong acids, weak bases, strong bases
Dweak bases, strong bases, strong acids, weak acids
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50May / June 2017 · Paper 11 · Q31Show mark scheme →
AThe calcium ions reacted with the ammonium ions, producing ammonia gas.
BThe calcium ions reacted with the nitrate ions, producing oxides of nitrogen.
CThe hydroxide ions reacted with the ammonium ions, producing ammonia gas.
DThe hydroxide ions reacted with the nitrate ions, producing oxides of nitrogen.
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51May / June 2017 · Paper 12 · Q19Show mark scheme →
ACarbon dioxide is formed.
BNeutralisation takes place.
COxidation takes place.
DWater is formed.
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52May / June 2017 · Paper 12 · Q20Show mark scheme →
AThey are partially ionised.
BThey do not react with metals.
CThey do not react with strong alkalis.
DTheir solutions have pH values in the range 0 to 2.
Mark scheme
53May / June 2017 · Paper 12 · Q21Show mark scheme →
Aammonia
Bcarbon dioxide
Cnitrogen dioxide
Dsulfur dioxide
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54May / June 2016 · Paper 11 · Q16Show mark scheme →
AH+
BOH–
CSO3 2–
DSO4 2–
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55May / June 2016 · Paper 12 · Q19Also set in May / June 2016 Paper 11Show mark scheme →
A1
B2
C7
D9
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