Acids And Bases

The conjugate base of ammonia (NH ) is formed when it donates a proton (H ). In this case, when ammonia loses a proton, it forms NH OH (hydroxylamine), which is the conjugate base. Thus, the correct answer is (D) NH OH.

So, the correct ans is (D):

1. Understanding the Relationship Between Kₐ and Conjugate Base Strength:
The strength of a conjugate base is inversely related to the strength of its parent acid. A weaker acid (smaller Kₐ) produces a stronger conjugate base. The Kₐ value represents the acid dissociation constant, and a smaller Kₐ indicates less dissociation, meaning the acid is weaker and its conjugate base is stronger.

2. Listing the Acids and Their Kₐ Values:
We are given:
- H₂SO₃: Kₐ = 1.3 × 10⁻²
- HNO₂: Kₐ = 4 × 10⁻⁴
- CH₃COOH: Kₐ = 1.8 × 10⁻⁵
- HCN: Kₐ = 4 × 10⁻¹⁰

3. Comparing the Kₐ Values:
To find the weakest acid, we compare the Kₐ values. The smaller the Kₐ, the weaker the acid, and thus the stronger its conjugate base:
- H₂SO₃: 1.3 × 10⁻² (largest Kₐ, strongest acid)
- HNO₂: 4 × 10⁻⁴
- CH₃COOH: 1.8 × 10⁻⁵
- HCN: 4 × 10⁻¹⁰ (smallest Kₐ, weakest acid)

4. Identifying the Weakest Acid:
HCN has the smallest Kₐ value (4 × 10⁻¹⁰), making it the weakest acid among the given options.

5. Determining the Strongest Conjugate Base:
The conjugate base of HCN is CN⁻. Since HCN is the weakest acid, CN⁻ is the strongest conjugate base in aqueous solution.

Final Answer:
The acid that produces the strongest conjugate base is HCN, so the answer is (D) HCN.

The strength of a conjugate base is inversely related to the strength of its corresponding acid. This means that as the acid becomes weaker, its conjugate base becomes stronger. The strength of an acid is represented by its dissociation constant, . A lower value indicates a weaker acid.

Given the values:

• :
• :
• :
• :

From these values, has the smallest value. Therefore, it is the weakest acid among the given options, making its conjugate base, , the strongest.

Let's summarize why is the correct answer:

• The smallest value corresponds to , making it the weakest acid.
• The weaker the acid, the stronger its conjugate base.
• Hence, , derived from , is the strongest conjugate base among the options.

When a weak acid and a weak base are mixed in equal proportions, the resulting solution forms a buffer. The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation:

Henderson-Hasselbalch equation:

Since the concentrations of the acid and its conjugate base are equal, the ratio is 1, so the equation simplifies to:

However, we also need to take into account the relationship between pKa and pKb for the conjugate acid-base pair. The equation linking pKa and pKb is:

Substituting the given values for pKa and pKb: The pH of the buffer solution is approximately the average of the pKa and pKb values, giving:

Conclusion:

The correct pH of the resulting solution is 7.05.

Answer: Option B: 7.05