Which one of the following acids has highest heat of neutralization with one equivalent of NaOH?

Options

A. HCl
B. HF
C. `H_2SO_4`
D. HCN

Answer

To determine which acid has the highest heat of neutralization with one equivalent of NaOH, we can follow these steps:

### Step 1: Understand the Concept of Heat of Neutralization
The heat of neutralization is defined as the amount of energy released when one mole of an acid reacts with one mole of a base to form a neutral solution (salt and water).

**Hint:** Remember that strong acids and strong bases typically release more heat during neutralization compared to weak acids and weak bases.

### Step 2: Identify the Acids
The acids provided in the question are:
1. Hydrochloric acid (HCl)
2. Hydrogen fluoride (HF)
3. Sulfuric acid (H₂SO₄)
4. Hydrogen cyanide (HCN)

**Hint:** Classify the acids into strong and weak categories. Strong acids will generally have higher heat of neutralization.

### Step 3: Classify the Acids
- **Hydrochloric acid (HCl)**: Strong acid
- **Hydrogen fluoride (HF)**: Weak acid
- **Sulfuric acid (H₂SO₄)**: Strong acid (first dissociation is strong)
- **Hydrogen cyanide (HCN)**: Weak acid

**Hint:** Strong acids completely dissociate in solution, while weak acids do not.

### Step 4: Determine the Strongest Acid
Among the strong acids listed, sulfuric acid (H₂SO₄) is the strongest because it has two dissociable protons, while hydrochloric acid (HCl) has only one.

**Hint:** The strength of an acid can often be determined by its ability to donate protons (H⁺ ions).

### Step 5: Analyze the Heat of Neutralization
The heat of neutralization is highest when a strong acid reacts with a strong base. Since NaOH is a strong base, we need to pair it with the strongest acid available.

**Hint:** The reaction of a strong acid with a strong base will yield the highest amount of heat.

### Step 6: Write the Reaction for Sulfuric Acid
The balanced reaction for sulfuric acid with sodium hydroxide is:
\[ \text{H}_2\text{SO}_4 + 2 \text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + 2 \text{H}_2\text{O} \]

Since we are considering only one equivalent of NaOH, we can focus on the first dissociation of sulfuric acid:
\[ \text{H}_2\text{SO}_4 + \text{NaOH} \rightarrow \text{NaHSO}_4 + \text{H}_2\text{O} \]

**Hint:** Always ensure the reaction is balanced to accurately determine the heat of reaction.

### Conclusion
Among the given acids, sulfuric acid (H₂SO₄) will produce the highest heat of neutralization when reacting with one equivalent of NaOH due to its strong acidic nature.

**Final Answer:** Sulfuric acid (H₂SO₄) has the highest heat of neutralization with one equivalent of NaOH.