Which one of the following must be added to dilute hydrochloric acid to produce hydrogen?

A. Iron

B. Iron sulfide

C. Copper chloride

D. Sulfur

Answer Explanation:

A. Iron (Correct Answer): Iron can react with hydrochloric acid to produce hydrogen gas according to the following reaction:

2HCl + Fe => FeCl2 + H2

So, adding iron to dilute hydrochloric acid would produce hydrogen gas.

B. Iron sulfide: Iron sulfide may react with hydrochloric acid, but it does not directly produce hydrogen gas. The reaction would likely produce hydrogen sulfide gas instead.

C. Copper chloride: Copper chloride does not react with hydrochloric acid to produce hydrogen gas. The reaction between copper chloride and hydrochloric acid would likely produce copper chloride and hydrogen chloride gas.

D. Sulfur: Sulfur does not react with hydrochloric acid to produce hydrogen gas. The reaction between sulfur and hydrochloric acid would likely produce hydrogen sulfide gas.

Therefore, the Correct Answer is A.

Q #1: Which statement regarding metal and non-metal oxides is not true?

A. Metal oxides are bases and forms alkalis in water.

B. Non-metal oxides form acids in water.

C. Solutions of non-metal oxides change red litmus blue.

D. Metal oxides color universal indicator blue and non-metal oxides color it red.

Answer Explanation

A. Metal oxides are bases and form alkalis in water: This statement is generally true. Metal oxides typically react with water to form basic solutions (alkalis). Therefore, this statement is true.

B. Non-metal oxides form acids in water: This statement is generally true. Non-metal oxides typically react with water to form acidic solutions. Therefore, this statement is true.

C. Solutions of non-metal oxides change red litmus blue: This statement is not true. Non-metal oxides typically form acidic solutions in water, which would not change red litmus paper to blue. Instead, they would typically turn blue litmus paper red.

D. Metal oxides color universal indicator blue and non-metal oxides color it red: This statement is generally true. Metal oxides tend to produce basic solutions, which turn universal indicator blue. Non-metal oxides tend to produce acidic solutions, which turn universal indicator red. Therefore, this statement is true.
Q #2: Why is NaCl neutral?

A. Because it contains both hydrogen and hydroxide ions in equal amounts

B. Because it contains hydrogen ions (H+) and hydroxide ions (OH-) in equal amounts

C. Because it does not contain any hydrogen or hydroxide ions

D. Because it dissociates completely in water

Answer Explanation

Rationale for each choice:

A) Because it contains both hydrogen and hydroxide ions in equal amounts: This statement is incorrect. NaCl (sodium chloride) does not contain hydrogen or hydroxide ions. It dissociates into sodium ions (Na+) and chloride ions (Cl-) in water, not hydrogen or hydroxide ions.

B) Because it contains hydrogen ions (H+) and hydroxide ions (OH-) in equal amounts: This statement is incorrect. NaCl does not contain hydrogen or hydroxide ions. In aqueous solution, NaCl dissociates into sodium ions and chloride ions, not hydrogen or hydroxide ions.

C) Because it does not contain any hydrogen or hydroxide ions (Correct Answer): NaCl is a neutral compound composed of sodium ions (Na+) and chloride ions (Cl-). It does not contain any hydrogen or hydroxide ions, so it is neutral in aqueous solution.

D) Because it dissociates completely in water: NaCl does dissociate in water, but its dissociation does not involve the generation of hydrogen or hydroxide ions. It dissociates into sodium ions and chloride ions, which do not contribute to the pH of the solution. Therefore, the completeness of dissociation does not determine its neutrality.
Q #3: Why is KOH a strong alkali?

A. Because it reacts vigorously with acids

B. Because it forms a basic solution when dissolved in water

C. Because in solution it fully dissociates into K+ and OH-

D. Because it forms insoluble precipitates with metal cations

Answer Explanation

A) Because it reacts vigorously with acids: While KOH does react with acids to form salts and water, the strength of an alkali is not solely determined by its reactivity with acids.

B) Because it forms a basic solution when dissolved in water: This statement is true, but it does not fully explain why KOH is considered a strong alkali. Many compounds can form basic solutions when dissolved in water.

C) Because in solution it fully dissociates into K+ and OH- (Correct Answer): KOH is considered a strong alkali because it fully dissociates in aqueous solution into potassium ions (K+) and hydroxide ions (OH-). This dissociation leads to a high concentration of hydroxide ions in solution, making it strongly alkaline.

D) Because it forms insoluble precipitates with metal cations: This statement describes the formation of insoluble hydroxide precipitates when alkali solutions are added to solutions of metal salts. However, it does not fully explain why KOH itself is considered a strong alkali.

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Which one of the following must be added to dilute hydrochloric acid to produce hydrogen?

More Questions on TEAS 7 Science

Q #1: Which statement regarding metal and non-metal oxides is not true?

Answer Explanation

Q #2: Why is NaCl neutral?

Answer Explanation

Q #3: Why is KOH a strong alkali?

Answer Explanation

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