1.6 Which ONE of the following is a CORRECT description for a 0.1 mol·dm⁻³ hydrochloric acid solution?
A) Dilute strong acid
B) Dilute weak acid
C) Concentrated weak acid
D) Concentrated strong acid
1.7 Consider the reactant Y in the following reaction:
Y + H₂O ⇌ H₃O⁺ + H₂PO₄⁻
A) PO₄³⁻
B) H₂PO₄⁻
C) HPO₄²⁻
D) H₃PO₄
1.8 An aqueous solution that contains more hydronium ions than hydroxide ions is a(n)
A) basic solution
B) acidic solution
C) neutral solution
D) standardised solution
1.9 Consider the reaction represented by the equation below:
H₃PO₄(aq) + HCO₃⁻(aq) ⇌ H₂PO₄⁻(aq) + H₂CO₃(aq) Kₐ > 1
The strongest base in the above reaction is:
A) H₂PO₄⁻
B) HCO₃⁻
C) H₃PO₄
D) H₂CO₃
Answer (2)
Let's go through each question one by one to find the correct answers.
1.6. Description of 0.1 mol·dm⁻³ hydrochloric acid (HCl) solution:
Option A: Dilute strong acid is the correct choice.
Hydrochloric acid (HCl) is a strong acid because it completely dissociates in water. A concentration of 0.1 mol·dm⁻³ indicates that the solution is dilute, as it is much less concentrated than typical laboratory-grade hydrochloric acid solutions.
1.7. Identify reactant Y in the equation:
The equation is: Y + H₂O ⇌ H₃O⁺ + H₂PO₄⁻
To determine Y, consider the products:
H₂PO₄⁻ is produced from the loss of a proton (H⁺) by H₃PO₄ (phosphoric acid), thus making the reactant Y: H₃PO₄ .
Option D: H₃PO₄ is the correct answer.
1.8. Aqueous solution with more hydronium ions than hydroxide ions:
An aqueous solution with more hydronium ions (H₃O⁺) than hydroxide ions (OH⁻) is considered acidic.
Option B: Acidic solution is the correct choice.
1.9. Identify the strongest base in the reaction:
The reaction is:
H₃PO₄(aq) + HCO₃⁻(aq) ⇌ H₂PO₄⁻(aq) + H₂CO₃(aq)
Given that Kₐ > 1, the equilibrium favors the formation of the products, implying the base on the product side, HCO₃⁻, is stronger.
Option B: HCO₃⁻ is the strongest base in this reaction.
Overall, the answers we chose are:
1.6: Option A
1.7: Option D
1.8: Option B
1.9: Option B
The answers are as follows: 1.6 - Option A (Dilute strong acid), 1.7 - Option D (H₃PO₄), 1.8 - Option B (Acidic solution), and 1.9 - Option B (HCO₃⁻ as the strongest base).
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