Acids, Bases, Alkalis, Salts, Neutralisation and pH

1. A student adds excess solid copper(II) oxide to warm dilute sulfuric acid. The mixture is filtered and the filtrate is gently heated until crystallisation starts.

Which salt is prepared?

A copper(II) sulfide
B copper(II) sulfate
C copper(II) sulfite
D copper(II) carbonate

2. Which statement correctly distinguishes an alkali from a base?

A An alkali neutralises acids, but a base does not.
B An alkali is a soluble base that produces OH– ions in water.
C A base is always soluble, but an alkali is always insoluble.
D An alkali reacts only with metals, but a base reacts only with acids.

3. A solution has pH 3. Another solution has pH 6.

Which statement is correct?

A pH 3 is less acidic than pH 6.
B pH 3 has a lower concentration of hydrogen ions than pH 6.
C pH 3 is more acidic than pH 6.
D Both solutions are alkaline because their pH values are below 7.

4. Which equation correctly represents neutralisation?

A H+(aq) + OH–(aq) → H2O(l)
B H2(g) + O2(g) → H2O(l)
C Na+(aq) + Cl–(aq) → NaCl(aq)
D CO3 2–(aq) + 2H+(aq) → CO2(g) + H2O(l)

5. Which substance reacts with dilute hydrochloric acid to form a salt, water and carbon dioxide?

A magnesium
B sodium hydroxide
C copper(II) carbonate
D ammonia

6. A student wants to prepare pure dry crystals of potassium nitrate.

Which method is most suitable?

A add excess potassium carbonate to nitric acid, filter, crystallise
B titrate potassium hydroxide with nitric acid, repeat without indicator, crystallise
C add potassium metal to nitric acid, evaporate to dryness
D mix potassium chloride and nitric acid, filter, dry the residue

7. Which pair of substances reacts to form ammonium sulfate?

A ammonia and sulfuric acid
B ammonium hydroxide and hydrochloric acid
C ammonia and nitric acid
D ammonium chloride and sodium sulfate

8. Which oxide is amphoteric?

A sodium oxide
B magnesium oxide
C aluminium oxide
D sulfur dioxide

9. Which substance is a weak acid?

A hydrochloric acid
B sulfuric acid
C nitric acid
D ethanoic acid

10. Which statement about acid strength and acid concentration is correct?

A A dilute acid must be weak.
B A concentrated acid must be strong.
C Strength depends on degree of ionisation; concentration depends on amount dissolved per dm3.
D Strength and concentration always mean the same thing.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

11. A solution turns blue litmus red but does not react with calcium carbonate.

Which conclusion is safest?

A It is definitely an acid.
B It is definitely an alkali.
C It may be acidic, but the carbonate test result is unusual and more tests are needed.
D It must be pure water.

12. A student prepares copper(II) chloride by reacting copper(II) oxide with dilute hydrochloric acid.

Why is excess copper(II) oxide added?

A to make sure all the copper(II) oxide reacts
B to make sure all the acid is used up
C to make the salt insoluble
D to make chlorine gas

13. After adding excess copper(II) oxide to hydrochloric acid, why is the mixture filtered?

A to remove unreacted copper(II) oxide
B to remove dissolved copper(II) chloride
C to remove water
D to remove hydrochloric acid gas

14. Which salt is formed when calcium carbonate reacts with nitric acid?

A calcium nitrite
B calcium nitrate
C calcium carbonate nitrate
D calcium nitrogen oxide

15. Which equation is correctly balanced?

A CaCO3 + HCl → CaCl2 + H2O + CO2
B CaCO3 + 2HCl → CaCl2 + H2O + CO2
C CaCO3 + H2Cl2 → CaCl2 + H2O + CO2
D CaCO3 + 2HCl → CaCl + H2O + CO2

16. Which salt is insoluble in water?

A sodium nitrate
B potassium sulfate
C silver chloride
D ammonium chloride

17. Which pair of solutions forms a precipitate when mixed?

A sodium chloride and potassium nitrate
B barium chloride and sodium sulfate
C sodium nitrate and potassium chloride
D ammonium sulfate and sodium nitrate

18. Which ionic equation represents the formation of barium sulfate precipitate?

A Ba2+(aq) + SO4 2–(aq) → BaSO4(s)
B Ba+(aq) + SO4 2–(aq) → BaSO4(s)
C Ba2+(aq) + S2–(aq) → BaS(s)
D BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)

19. A student wants to prepare lead(II) iodide.

Which method is most suitable?

A warm lead with iodine until it melts
B mix aqueous lead(II) nitrate with aqueous potassium iodide, filter and dry the precipitate
C add excess lead(II) oxide to hydroiodic acid and crystallise
D titrate lead(II) hydroxide with potassium iodide

20. Which salt can be prepared by adding excess zinc carbonate to dilute sulfuric acid?

A zinc chloride
B zinc nitrate
C zinc sulfate
D zinc sulfide

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

21. Which observation shows that a metal is reacting with dilute acid?

A a white precipitate forms immediately
B bubbles of hydrogen gas are produced
C carbon dioxide turns limewater milky
D the acid turns blue litmus red

22. Which metal will not normally react with dilute hydrochloric acid to produce hydrogen?

A magnesium
B zinc
C iron
D copper

23. Which reaction produces a salt and water only?

A hydrochloric acid + magnesium
B hydrochloric acid + sodium hydroxide
C hydrochloric acid + calcium carbonate
D hydrochloric acid + ammonium carbonate

24. Which salt is formed when ammonia reacts with hydrochloric acid?

A ammonium chloride
B ammonium nitrate
C ammonium sulfate
D ammonia chloride

25. Which statement about pH is correct?

A pH 1 is weakly acidic.
B pH 7 is neutral.
C pH 10 is strongly acidic.
D pH 14 is neutral.

26. A solution changes methyl orange from orange to red.

Which conclusion is correct?

A The solution is acidic.
B The solution is neutral.
C The solution is alkaline.
D The solution contains carbonate ions.

27. Phenolphthalein is colourless in solution X and pink in solution Y.

Which row is most likely correct?

	X	Y
A	acid	alkali
B	alkali	acid
C	neutral	acid
D	alkali	neutral

28. A student adds sodium hydroxide solution to hydrochloric acid until the pH becomes 7.

Which statement is correct?

A The final solution contains only water.
B The final solution contains sodium chloride and water.
C Hydrogen gas is produced.
D Carbon dioxide is produced.

29. Which acid is needed to prepare copper(II) nitrate from copper(II) oxide?

A hydrochloric acid
B sulfuric acid
C nitric acid
D ethanoic acid

30. Which acid is needed to prepare zinc sulfate from zinc carbonate?

A hydrochloric acid
B sulfuric acid
C nitric acid
D carbonic acid

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

31. A salt is made by reacting an acid with an alkali using titration. Why is titration needed?

A Both reactants are soluble, so excess reactant cannot be removed by filtration.
B The salt formed is insoluble.
C The acid is always weak.
D The alkali is always coloured.

32. Which salt preparation method is best for making sodium sulfate crystals?

A excess sodium oxide with sulfuric acid, then filter
B sodium hydroxide solution titrated with sulfuric acid, then crystallise
C sodium chloride solution mixed with sulfuric acid, then filter
D sodium metal added to sulfuric acid, then evaporate strongly

33. Which statement about soluble salts is correct?

A All sulfates are soluble.
B All carbonates are soluble.
C All nitrates are soluble.
D All chlorides are insoluble.

34. Which salt is soluble in water?

A calcium carbonate
B silver chloride
C lead(II) sulfate
D sodium carbonate

35. Which salt is insoluble in water?

A potassium nitrate
B ammonium sulfate
C calcium carbonate
D sodium chloride

36. Which reaction can be used to prepare magnesium chloride crystals safely?

A magnesium carbonate + dilute hydrochloric acid
B magnesium + concentrated hydrochloric acid, evaporated to dryness
C magnesium oxide + sodium chloride solution
D magnesium sulfate + hydrochloric acid

37. Which gas is produced when ammonium chloride is warmed with sodium hydroxide solution?

A hydrogen
B ammonia
C carbon dioxide
D chlorine

38. Which statement about bases is correct?

A All bases dissolve in water.
B Bases neutralise acids.
C Bases are always liquids.
D Bases always produce hydrogen with metals.

39. Which oxide reacts with sodium hydroxide solution?

A magnesium oxide
B sodium oxide
C aluminium oxide
D carbon monoxide

40. Which oxide reacts with hydrochloric acid but not with sodium hydroxide?

A sulfur dioxide
B carbon dioxide
C magnesium oxide
D aluminium oxide

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

41. Which statement about a strong acid is correct?

A It is always concentrated.
B It completely ionises in water.
C It has pH exactly 7.
D It reacts only with strong alkalis.

42. Which statement about a weak acid is correct?

A It does not contain hydrogen.
B It partially ionises in water.
C It cannot neutralise an alkali.
D It always has pH above 7.

43. Equal volumes of 0.100 mol/dm3 hydrochloric acid and 0.100 mol/dm3 ethanoic acid are compared.

Which statement is correct?

A They contain the same total amount of acid molecules/formula units, but different concentrations of H+(aq).
B They contain the same concentration of H+(aq) because both are acids.
C Ethanoic acid has lower pH because it is weak.
D Hydrochloric acid is weaker because it has fewer atoms.

44. Which solution has the greatest concentration of hydroxide ions?

A pH 2
B pH 6
C pH 9
D pH 13

45. Which change will increase the pH of dilute hydrochloric acid?

A adding distilled water
B adding more hydrochloric acid
C adding sulfuric acid
D adding carbon dioxide

46. A solution of sodium hydroxide has pH 13. It is diluted with water.

Which pH is most likely after dilution?

A 1
B 7
C 11
D 14

47. An acid reacts with an unknown solid. Bubbles are produced. The gas turns limewater milky.

What is the solid most likely to contain?

A nitrate ions
B sulfate ions
C carbonate ions
D chloride ions

48. A solid reacts with dilute hydrochloric acid to produce a gas that gives a squeaky pop with a lighted splint.

Which solid could be used?

A calcium carbonate
B zinc
C copper(II) oxide
D sodium hydroxide

49. A solution reacts with both hydrochloric acid and sodium hydroxide.

Which substance could it contain?

A aluminium oxide
B sodium chloride
C magnesium chloride
D potassium nitrate

50. Which row correctly matches the reactants, salt formed and extra product?

	reactants	salt formed	extra product
A	acid + metal	salt	carbon dioxide
B	acid + carbonate	salt	hydrogen
C	acid + alkali	salt	water
D	acid + ammonium salt	salt	oxygen

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

1. B

A wrong: Copper(II) sulfide would need sulfide ions, not sulfuric acid.
B right: Copper(II) oxide + sulfuric acid → copper(II) sulfate + water.
C wrong: Sulfite comes from sulfurous acid/sulfite ions, not sulfuric acid.
D wrong: Carbonate comes from carbonate ions.

2. B

A wrong: Both alkalis and bases neutralise acids.
B right: An alkali is a soluble base that produces OH– ions in water.
C wrong: This is reversed and false.
D wrong: Bases and alkalis both react with acids.

3. C

A wrong: Lower pH means more acidic.
B wrong: pH 3 has a higher H+ concentration than pH 6.
C right: pH 3 is more acidic than pH 6.
D wrong: pH below 7 is acidic, not alkaline.

4. A

A right: Neutralisation is H+(aq) + OH–(aq) → H2O(l).
B wrong: This is combustion/formation of water.
C wrong: This shows ions forming sodium chloride, not neutralisation.
D wrong: This is acid + carbonate reaction, not the basic neutralisation ionic equation.

5. C

A wrong: Magnesium + acid gives salt + hydrogen.
B wrong: Sodium hydroxide + acid gives salt + water only.
C right: Copper(II) carbonate + acid gives salt + water + carbon dioxide.
D wrong: Ammonia + acid gives ammonium salt only.

6. B

A wrong: Potassium carbonate is soluble, so excess cannot be removed cleanly by filtration.
B right: Potassium nitrate is soluble and made from acid + alkali by titration, then crystallisation.
C wrong: Potassium metal with nitric acid is unsafe and unsuitable.
D wrong: Mixing potassium chloride and nitric acid does not give pure potassium nitrate crystals this way.

7. A

A right: Ammonia + sulfuric acid → ammonium sulfate.
B wrong: This forms ammonium chloride.
C wrong: This forms ammonium nitrate.
D wrong: Mixing soluble salts is not the proper preparation here.

8. C

A wrong: Sodium oxide is basic.
B wrong: Magnesium oxide is basic.
C right: Aluminium oxide is amphoteric because it reacts with both acids and alkalis.
D wrong: Sulfur dioxide is acidic.

9. D

A wrong: Hydrochloric acid is strong.
B wrong: Sulfuric acid is strong.
C wrong: Nitric acid is strong.
D right: Ethanoic acid is weak because it only partially ionises in water.

10. C

A wrong: Dilute means low concentration, not weak ionisation.
B wrong: Concentrated means high amount dissolved, not necessarily strong.
C right: Strength depends on ionisation; concentration depends on amount of acid per dm3.
D wrong: Strength and concentration are different ideas.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

11. C

A wrong: Blue litmus turning red suggests acidity, but no reaction with calcium carbonate creates doubt.
B wrong: Alkalis turn red litmus blue, not blue litmus red.
C right: The safest conclusion is that it may be acidic, but more tests are needed because acids normally react with carbonates.
D wrong: Pure water is neutral and would not turn blue litmus red.

12. B

A wrong: The aim is not to use up all the oxide; excess oxide remains.
B right: Excess copper(II) oxide ensures all hydrochloric acid is used up, so no acid contaminates the crystals.
C wrong: Copper(II) chloride is soluble.
D wrong: Chlorine gas is not made.

13. A

A right: Filtration removes unreacted excess copper(II) oxide.
B wrong: Dissolved copper(II) chloride passes through as filtrate.
C wrong: Filtration does not remove water.
D wrong: Hydrochloric acid gas is not being filtered.

14. B

A wrong: Nitric acid forms nitrates, not nitrites.
B right: Calcium carbonate + nitric acid → calcium nitrate + water + carbon dioxide.
C wrong: “Calcium carbonate nitrate” is not the salt name.
D wrong: Not a correct salt name.

15. B

A wrong: Not balanced; needs 2HCl.
B right: CaCO3 + 2HCl → CaCl2 + H2O + CO2.
C wrong: H2Cl2 is not used as hydrochloric acid formula.
D wrong: Calcium chloride is CaCl2, not CaCl.

16. C

A wrong: Sodium nitrate is soluble.
B wrong: Potassium sulfate is soluble.
C right: Silver chloride is insoluble.
D wrong: Ammonium chloride is soluble.

17. B

A wrong: All possible products remain soluble.
B right: Barium sulfate forms as an insoluble white precipitate.
C wrong: All ions remain in solution.
D wrong: No insoluble salt forms.

18. A

A right: Ba2+(aq) + SO4 2–(aq) → BaSO4(s).
B wrong: Barium ion is Ba2+, not Ba+.
C wrong: This forms barium sulfide, not barium sulfate.
D wrong: This is the full equation, not the ionic equation.

19. B

A wrong: Direct heating is not the standard safe precipitation method.
B right: Lead(II) iodide is insoluble, so mix two soluble salts, filter and dry the precipitate.
C wrong: Hydroiodic acid is not the usual O Level method here.
D wrong: This is not a correct titration method for insoluble lead(II) iodide.

20. C

A wrong: Chloride needs hydrochloric acid.
B wrong: Nitrate needs nitric acid.
C right: Zinc carbonate + sulfuric acid → zinc sulfate + water + carbon dioxide.
D wrong: Sulfide needs sulfide ions.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

21. B

A wrong: Metal + acid does not usually produce a precipitate.
B right: Metal + acid produces hydrogen gas bubbles.
C wrong: Limewater turning milky shows carbon dioxide, usually from carbonate + acid.
D wrong: Acid turning blue litmus red only shows acidity, not metal reaction.

22. D

A wrong: Magnesium reacts with dilute hydrochloric acid.
B wrong: Zinc reacts with dilute hydrochloric acid.
C wrong: Iron reacts slowly with dilute hydrochloric acid.
D right: Copper is below hydrogen in the reactivity series and does not normally produce hydrogen with dilute hydrochloric acid.

23. B

A wrong: Acid + magnesium gives salt + hydrogen.
B right: Acid + sodium hydroxide gives salt + water only.
C wrong: Acid + carbonate gives salt + water + carbon dioxide.
D wrong: Acid + ammonium carbonate gives salt + water + carbon dioxide.

24. A

A right: Ammonia + hydrochloric acid → ammonium chloride.
B wrong: Ammonium nitrate needs nitric acid.
C wrong: Ammonium sulfate needs sulfuric acid.
D wrong: “Ammonia chloride” is not the correct salt name.

25. B

A wrong: pH 1 is strongly acidic.
B right: pH 7 is neutral.
C wrong: pH 10 is alkaline.
D wrong: pH 14 is strongly alkaline.

26. A

A right: Methyl orange turns red in acidic solution.
B wrong: Neutral solution gives orange/yellowish result, not red.
C wrong: Alkalis turn methyl orange yellow.
D wrong: Methyl orange does not specifically test carbonate ions.

27. A

A right: Phenolphthalein is colourless in acid and pink in alkali.
B wrong: Reversed.
C wrong: Phenolphthalein is not pink in acid.
D wrong: Phenolphthalein is not colourless in strong alkali.

28. B

A wrong: Neutralisation does not remove dissolved salt.
B right: NaOH + HCl → NaCl + H2O, so final solution contains sodium chloride and water.
C wrong: Hydrogen gas forms with acid + reactive metal.
D wrong: Carbon dioxide forms with acid + carbonate.

29. C

A wrong: Hydrochloric acid forms copper(II) chloride.
B wrong: Sulfuric acid forms copper(II) sulfate.
C right: Nitric acid forms copper(II) nitrate.
D wrong: Ethanoic acid forms copper(II) ethanoate.

30. B

A wrong: Hydrochloric acid forms zinc chloride.
B right: Sulfuric acid forms zinc sulfate.
C wrong: Nitric acid forms zinc nitrate.
D wrong: Carbonic acid is not used to make zinc sulfate.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

31. A

A right: Acid and alkali are both soluble, so excess cannot be filtered off; exact neutralisation by titration is needed.
B wrong: The salt made by titration is usually soluble.
C wrong: Titration is not needed because the acid is weak.
D wrong: Alkalis are usually colourless; indicator is added separately.

32. B

A wrong: Sodium oxide is reactive and not the best controlled method.
B right: Sodium sulfate is soluble, so use titration with sodium hydroxide and sulfuric acid, then crystallise.
C wrong: Mixing sodium chloride and sulfuric acid is not a clean salt-crystal preparation.
D wrong: Sodium metal is dangerous and strong evaporation may decompose/spit.

33. C

A wrong: Most sulfates are soluble, but barium sulfate and lead(II) sulfate are insoluble.
B wrong: Most carbonates are insoluble except Group I and ammonium carbonates.
C right: All nitrates are soluble.
D wrong: Most chlorides are soluble except silver chloride and lead(II) chloride.

34. D

A wrong: Calcium carbonate is insoluble.
B wrong: Silver chloride is insoluble.
C wrong: Lead(II) sulfate is insoluble.
D right: Sodium carbonate is soluble because all sodium salts are soluble.

35. C

A wrong: Potassium nitrate is soluble.
B wrong: Ammonium sulfate is soluble.
C right: Calcium carbonate is insoluble.
D wrong: Sodium chloride is soluble.

36. A

A right: Magnesium carbonate reacts safely with dilute hydrochloric acid to form magnesium chloride, water and carbon dioxide; excess solid can be filtered off.
B wrong: Concentrated acid and evaporating to dryness are unsafe/unsuitable.
C wrong: Magnesium oxide does not react with sodium chloride solution to form magnesium chloride.
D wrong: Magnesium sulfate + hydrochloric acid does not give a clean preparation of magnesium chloride.

37. B

A wrong: Hydrogen is produced by acid + metal, not ammonium salt + alkali.
B right: Ammonium salt + alkali on warming gives ammonia gas.
C wrong: Carbon dioxide comes from carbonates.
D wrong: Chlorine is not produced.

38. B

A wrong: Only soluble bases are alkalis; many bases are insoluble.
B right: Bases neutralise acids.
C wrong: Bases can be solids, such as copper(II) oxide.
D wrong: Metals produce hydrogen with acids, not bases.

39. C

A wrong: Magnesium oxide is basic and reacts with acids, not alkalis.
B wrong: Sodium oxide is basic.
C right: Aluminium oxide is amphoteric and reacts with sodium hydroxide.
D wrong: Carbon monoxide is neutral and does not react like this.

40. C

A wrong: Sulfur dioxide is acidic and reacts with alkalis, not acids.
B wrong: Carbon dioxide is acidic and reacts with alkalis.
C right: Magnesium oxide is basic, so it reacts with hydrochloric acid but not sodium hydroxide.
D wrong: Aluminium oxide is amphoteric and reacts with both acid and alkali.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

41. B

A wrong: Strong acid does not mean concentrated acid.
B right: A strong acid completely ionises in water.
C wrong: pH 7 is neutral.
D wrong: Strong acids react with weak and strong bases/alkalis.

42. B

A wrong: Weak acids still contain ionisable hydrogen.
B right: A weak acid partially ionises in water.
C wrong: Weak acids can neutralise alkalis.
D wrong: Weak acids still have pH below 7, though usually higher than a strong acid of same concentration.

43. A

A right: Equal volumes and equal concentrations mean same total acid amount, but HCl fully ionises while ethanoic acid partially ionises, so H+ concentration differs.
B wrong: Weak acids have lower H+ concentration than strong acids of same concentration.
C wrong: Ethanoic acid has higher pH than hydrochloric acid at the same concentration.
D wrong: Acid strength is not about number of atoms.

44. D

A wrong: pH 2 has high H+ and very low OH–.
B wrong: pH 6 is weakly acidic.
C wrong: pH 9 is alkaline but less alkaline than pH 13.
D right: pH 13 has the greatest hydroxide ion concentration.

45. A

A right: Adding distilled water dilutes the acid, lowers H+ concentration and increases pH towards 7.
B wrong: Adding more hydrochloric acid lowers pH.
C wrong: Adding sulfuric acid lowers pH.
D wrong: Carbon dioxide forms weak carbonic acid, so it will not increase pH.

46. C

A wrong: Diluting an alkali cannot make it strongly acidic.
B wrong: Dilution moves pH towards 7 but does not normally reach exactly 7 unless neutralised.
C right: pH may fall from 13 to around 11 after dilution.
D wrong: Dilution cannot make it more alkaline.

47. C

A wrong: Nitrates do not give CO2 with acid.
B wrong: Sulfates do not give CO2 with acid.
C right: Carbonates react with acids to produce CO2, which turns limewater milky.
D wrong: Chlorides do not give CO2 with acid.

48. B

A wrong: Calcium carbonate gives carbon dioxide.
B right: Zinc reacts with dilute hydrochloric acid to produce hydrogen, which gives a squeaky pop.
C wrong: Copper(II) oxide gives salt and water only.
D wrong: Sodium hydroxide gives salt and water only.

49. A

A right: Aluminium oxide is amphoteric, so it reacts with both acids and alkalis.
B wrong: Sodium chloride is neutral and does not react with both.
C wrong: Magnesium chloride is a salt, not amphoteric.
D wrong: Potassium nitrate is a neutral soluble salt.

50. C

A wrong: Acid + metal gives salt + hydrogen, not carbon dioxide.
B wrong: Acid + carbonate gives salt + water + carbon dioxide, not hydrogen.
C right: Acid + alkali gives salt + water.
D wrong: Acid + ammonium salt does not produce oxygen.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.