Which buffer solution out of the following will have `pH gt 7`?

Options

A. `CH_(3)COOH + CH_(3)COONa`
B. `HCOOH + HCOOK`
C. `CH_(3)COONH_(4)`
D. `NH_(4)OH +NH_(4)CI`

Explanation

To determine which buffer solution has a pH greater than 7, we need to analyze the components of each buffer solution provided in the options. Here’s a step-by-step solution:

### Step 1: Understand Buffer Solutions
Buffer solutions are typically composed of a weak acid and its conjugate base, or a weak base and its conjugate acid. They resist changes in pH when small amounts of strong acids or bases are added.

### Step 2: Identify the Characteristics of pH
- **pH < 7**: Indicates an acidic solution, often a combination of a strong acid and a weak base.
- **pH = 7**: Indicates a neutral solution, which can be a combination of strong acid and strong base or weak acid and weak base.
- **pH > 7**: Indicates a basic solution, often a combination of a strong base and a weak acid.

### Step 3: Analyze Each Option
1. **Option A: Acetic Acid (CH₃COOH) and Sodium Acetate (CH₃COONa)**
- Acetic acid is a weak acid, and sodium acetate is the salt of this weak acid. This combination will yield a pH less than 7.

2. **Option B: Formic Acid (HCOOH) and Sodium Formate (HCOONa)**
- Similar to acetic acid, formic acid is also a weak acid, and sodium formate is its salt. This combination will also yield a pH less than 7.

3. **Option C: Ammonium Acetate (CH₃COONH₄)**
- This is a salt formed from a strong acid (acetic acid) and a weak base (ammonia). The pH of this solution will be approximately 7.

4. **Option D: Sodium Hydroxide (NaOH) and Acetic Acid (CH₃COOH)**
- Sodium hydroxide is a strong base, and acetic acid is a weak acid. The combination of a strong base and a weak acid will yield a pH greater than 7.

### Step 4: Conclusion
Based on the analysis, the buffer solution that will have a pH greater than 7 is **Option D: Sodium Hydroxide and Acetic Acid**.

### Final Answer
The buffer solution that has a pH greater than 7 is **Option D**.

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