Quiz: Acids Bases and Salts — 19 questions

1. According to Arrhenius theory, what defines an acid in aqueous solution?

A. It ionizes in water to produce OH− ions.

B. It changes red litmus paper to blue.

C. It ionizes in water to produce H+ ions.

D. It accepts a proton from another substance.

Answer: (C)

Explanation

An Arrhenius acid is defined by its production of H+ ions when it ionizes in water. Producing OH− ions is the Arrhenius definition of a base, while proton acceptance belongs to Brønsted–Lowry theory.

2. Which substance fits the Arrhenius definition of a base when dissolved in water?

A. A substance that turns blue litmus red

B. A substance that produces H+ ions

C. A substance that donates a proton

D. A substance that produces OH− ions

Answer: (D)

Explanation

An Arrhenius base ionizes in water and produces OH− ions. H+ production identifies an Arrhenius acid, and proton donation is a Brønsted–Lowry acid behavior.

3. What does a Brønsted–Lowry acid do during an acid–base reaction?

A. It accepts a proton.

B. It neutralizes every dissolved salt.

C. It donates a proton.

D. It produces hydroxide ions in water.

Answer: (C)

Explanation

A Brønsted–Lowry acid is defined as a proton donor. Proton acceptance characterizes a Brønsted–Lowry base, whereas hydroxide production is associated with the Arrhenius definition of a base.

4. What role does a Brønsted–Lowry base play in a proton-transfer reaction?

A. It produces hydrogen ions in water.

B. It accepts a proton.

C. It donates a proton.

D. It changes every acid into a salt.

Answer: (B)

Explanation

A Brønsted–Lowry base accepts a proton from another species. Proton donation identifies a Brønsted–Lowry acid, while hydrogen-ion production is an Arrhenius acid concept.

5. In the reaction $HCl + H_2O \longrightarrow H_3O^+ + Cl^-$, which species acts as the Brønsted–Lowry base?

A. H2O, because it accepts a proton

B. Cl−, because it donates a proton

C. HCl, because it accepts a proton

D. H3O+, because it donates a proton

Answer: (A)

Explanation

Water accepts a proton from HCl and becomes H3O+, so it acts as the proton-accepting base. HCl is the proton donor and therefore acts as the acid in this reaction.

6. Why is water described as amphoteric in Brønsted–Lowry acid–base chemistry?

A. It can donate or accept a proton, depending on the reaction.

B. It produces both acid and base ions in every solution.

C. It has a constant role as the proton donor.

D. It reacts with water to form two neutral substances.

Answer: (A)

Explanation

Water is amphoteric because it can donate a proton in one reaction and accept a proton in another. Its role depends on the reaction partner rather than remaining fixed as an acid or base.

7. What happens when a strong acid dissolves in aqueous solution?

A. It remains molecular while transferring protons to water.

B. It ionizes partially, producing ions from a small fraction of the acid.

C. It ionizes completely, producing ions from 100% of the acid.

D. It produces hydroxide ions instead of hydrogen ions.

Answer: (C)

Explanation

A strong acid ionizes completely, or 100%, in aqueous solution; HCl, HNO3, and H2SO4 are examples. Partial ionization describes a weak acid, while hydroxide production characterizes a base.

8. Which description best explains why ethanoic acid is classified as a weak acid?

A. It produces more hydroxide ions than a strong base.

B. It ionizes completely, reaching 100% in water.

C. It cannot form ions when dissolved in water.

D. It ionizes only partially, reaching up to about 5% in water.

Answer: (D)

Explanation

Ethanoic acid is weak because it ionizes only partially in water, with ionization reaching up to about 5%. Complete ionization is characteristic of strong acids, not ethanoic acid.

9. Which statement correctly describes a strong base in aqueous solution?

A. It donates protons while remaining largely molecular.

B. It forms H+ ions instead of hydroxide ions.

C. It ionizes completely, or 100%, in water.

D. It ionizes to a small extent and produces few OH− ions.

Answer: (C)

Explanation

A strong base ionizes completely, or 100%, in aqueous solution; NaOH, KOH, and Ca(OH)2 are examples. Limited ionization and fewer OH− ions describe a weak base rather than a strong base.

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

A. An alkali is a base that contains a metal ion

B. An alkali is a base that reacts with every acid

C. An alkali is a base that changes blue litmus red

D. An alkali is a base that dissolves in water

Answer: (D)

Explanation

An alkali is defined as a base that is soluble in water, while some bases are insoluble. The reaction with acids and litmus behavior do not distinguish alkalis from other bases.

11. Which substance is a base but not an alkali because it does not dissolve in water?

A. Copper hydroxide

B. Potassium hydroxide

C. Sodium hydroxide

D. Aqueous ammonia

Answer: (A)

Explanation

Copper hydroxide is an insoluble metal hydroxide, so it is a base but not an alkali. Sodium hydroxide, potassium hydroxide, and aqueous ammonia are water-soluble bases.

12. What products form when an acid reacts with a metal?

A. A salt and hydrogen gas

B. Water and oxygen gas

C. A salt, water, and carbon dioxide

D. A base and hydrogen gas

Answer: (A)

Explanation

Acid–metal reactions produce a salt and hydrogen gas. Carbon dioxide is associated with acid–carbonate reactions, not ordinary acid–metal reactions.

13. A carbonate sample is added to an acid and bubbles of gas appear. Which products are expected from this reaction?

A. A metal and carbon dioxide

B. A salt, water, and carbon dioxide

C. A salt and hydrogen gas

D. A base, water, and oxygen

Answer: (B)

Explanation

Acids reacting with metal carbonates form a salt, water, and carbon dioxide, which causes the bubbling. Hydrogen gas is produced when an acid reacts with a suitable metal instead.

14. Which reaction is classified as neutralization?

A. An acid reacting with a base to form salt and water

B. An acid reacting with a metal to form salt and hydrogen

C. A base decomposing an ammonium salt to release ammonia

D. An acid reacting with a carbonate to form carbon dioxide

Answer: (A)

Explanation

Neutralization occurs when an acid and a base react to produce a salt and water. The other reactions describe acid–metal, acid–carbonate, or base–ammonium salt processes.

15. What happens when a base neutralizes an acid?

A. They form a carbonate and oxygen

B. They form hydrogen and a metal oxide

C. They form a salt and water

D. They form ammonia and carbon dioxide

Answer: (C)

Explanation

Bases neutralize acids by producing salt and water. Ammonia formation instead occurs when a base reacts with an ammonium salt, particularly on heating.

16. What gas is liberated when a base decomposes an ammonium salt on heating?

A. Carbon dioxide

B. Hydrogen

C. Oxygen

D. Ammonia

Answer: (D)

Explanation

Heating a base with an ammonium salt causes decomposition and liberates ammonia gas. Hydrogen and carbon dioxide are characteristic products of different acid reactions.

17. What makes acid rain more acidic than normal rain?

A. Suspended metal particles produce sodium and potassium acids

B. Evaporated water produces phosphoric and nitric acids

C. Dissolved oxygen produces hydrochloric and carbonic acids

D. Dissolved acid oxides produce nitric and sulphuric acids

Answer: (D)

Explanation

Acid rain forms when atmospheric acid oxides dissolve in rainwater and produce nitric and sulphuric acids. Normal rain is only slightly acidic because it contains dissolved carbon dioxide, not because it contains these stronger acids.

18. A marble statue and an iron railing are exposed to acid rain for many years. Why can both structures be damaged?

A. Acid rain removes oxygen from metals and carbonates

B. Acid rain converts all surface materials into neutral salts

C. Acid rain freezes inside both materials and causes expansion

D. Acid rain corrodes metals and reacts with metal carbonates

Answer: (D)

Explanation

The corrosive nature of acid rain allows it to damage structures containing metals and metal carbonates, such as iron railings and marble statues. Freezing can damage materials in some conditions, but it is not the relevant effect of acid rain here.

19. Which sequence correctly describes the formation of a metal hydroxide from a metal?

A. A metal reacts with oxygen to form an oxide, which reacts with water

B. A metal reacts with water to form an oxide, which reacts with nitrogen

C. A metal reacts with an acid to form a salt, which reacts with hydrogen

D. A metal reacts with carbon dioxide to form a carbonate, which reacts with oxygen

Answer: (A)

Explanation

Metals first react with oxygen to form metal oxides, and those oxides can then react with water to form metal hydroxides. The other sequences describe different substances or reactions and do not represent this oxide-to-hydroxide process.