In some solutions, the concentration of `H_(3)O^(+)` remains constant even when small amounts of strong acid or strong base are added to them. These solutions are known as :

Options

A. Ideal solutions
B. Colloidal solutions
C. True solutions
D. Buffer solutions

Answer

To solve the question, we need to understand the concept of solutions that maintain a constant concentration of \( H_3O^+ \) ions even when small amounts of strong acids or bases are added. Let's break down the reasoning step by step:

### Step 1: Understanding \( H_3O^+ \) Concentration
- The concentration of \( H_3O^+ \) ions in a solution is a measure of its acidity. In pure water, this concentration is \( 1 \times 10^{-7} \, \text{M} \) at 25°C.

### Step 2: Effect of Strong Acids and Bases
- Strong acids, when added to a solution, dissociate completely to produce \( H_3O^+ \) ions. For example, adding hydrochloric acid (HCl) will increase the concentration of \( H_3O^+ \).
- Strong bases, on the other hand, produce hydroxide ions (\( OH^- \)), which can react with \( H_3O^+ \) ions to form water, potentially decreasing the concentration of \( H_3O^+ \).

### Step 3: Buffer Solutions
- A buffer solution is designed to resist changes in pH when small amounts of acids or bases are added. It typically consists of a weak acid and its conjugate base (or a weak base and its conjugate acid).
- When a strong acid is added to a buffer, the weak acid component of the buffer can react with the added \( H_3O^+ \) ions, minimizing the change in concentration.
- Similarly, when a strong base is added, the conjugate base of the weak acid can react with \( OH^- \) ions, again minimizing the change in \( H_3O^+ \) concentration.

### Step 4: Conclusion
- Therefore, the solutions that maintain a constant concentration of \( H_3O^+ \) ions upon the addition of small amounts of strong acids or bases are known as **buffer solutions**.

### Final Answer
The solutions are known as **buffer solutions**.

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