Choose the correct statement (s) out of the following

Options

A. In `CH_(3)COOH //CH_(3)COONa ` buffer , the reserve acjdity of the solution is due to `CH_(3)COO^(-)` ions
B. It is not necessary that an acidic substance must contain hydrogen ions
C. `HCO_(3)^(-)` is both Bronsted base and Bronsted acid
D. Sodium carbonate does not contain `OH^(-)` ions and thus is not a base

Answer

To solve the question, we need to evaluate each statement provided and determine whether it is correct or incorrect. Let's analyze each option step by step.

### Step 1: Evaluate the First Statement
**Statement:** In sodium acetate buffer (CH3COONa), acetic acid (CH3COOH) is a weak acid which, after giving H⁺, gives a conjugate base (CH3COO⁻).

**Analysis:**
- Acetic acid (CH3COOH) is indeed a weak acid.
- When it donates a proton (H⁺), it forms its conjugate base, acetate ion (CH3COO⁻).
- The acetate ion can hydrolyze in solution, which contributes to the buffer's ability to resist changes in pH.

**Conclusion:** This statement is correct.

### Step 2: Evaluate the Second Statement
**Statement:** It is not necessary that an acidic substance must contain hydrogen.

**Analysis:**
- The example of boric acid (B(OH)3) is provided, which does not contain ionizable hydrogen but can still act as an acid by accepting hydroxide ions (OH⁻) and releasing H⁺ into the solution.
- This shows that acidity can be defined by the ability to accept protons rather than the presence of hydrogen atoms.

**Conclusion:** This statement is correct.

### Step 3: Evaluate the Third Statement
**Statement:** HCO3⁻ is both a Brønsted base and a Brønsted acid.

**Analysis:**
- HCO3⁻ (bicarbonate ion) can accept a proton (acting as a Brønsted base) to form H2CO3 (carbonic acid).
- It can also donate a proton (acting as a Brønsted acid) to form CO3²⁻ (carbonate ion).
- This dual behavior confirms that HCO3⁻ can act as both an acid and a base.

**Conclusion:** This statement is correct.

### Step 4: Evaluate the Fourth Statement
**Statement:** Sodium carbonate (Na2CO3) does not contain OH⁻ ions, thus does not act as a base.

**Analysis:**
- Sodium carbonate dissociates in solution to form Na⁺ ions and CO3²⁻ ions.
- CO3²⁻ comes from carbonic acid (H2CO3), which is a weak acid. Therefore, CO3²⁻ can act as a base by accepting protons (H⁺).
- Even though Na2CO3 does not contain OH⁻ ions, it can still act as a base due to the presence of CO3²⁻ ions.

**Conclusion:** This statement is incorrect.

### Final Conclusion
The correct statements are:
1. First statement is correct.
2. Second statement is correct.
3. Third statement is correct.
4. Fourth statement is incorrect.

### Summary of Correct Statements:
- The correct statements are the first, second, and third options.

---