Which of the following is the strongest base ?

Options

A. `C_2H_5^-`
B. `C_2H_5COO^-`
C. `C_2H_5O^-`
D. `OH^-`

Answer

To determine which of the following compounds is the strongest base, we need to analyze the conjugate acids of each option. The strength of a base is inversely related to the strength of its conjugate acid; that is, a strong base will have a weak conjugate acid.

### Step-by-Step Solution:

1. **Identify the Compounds**:
The options given are:
- A) C2H6 (Ethane)
- B) C2H5COOH (Acetic Acid)
- C) C2H5OH (Ethanol)
- D) H2O (Water)

2. **Determine the Conjugate Acids**:
- A) C2H6 is a neutral molecule and does not have a conjugate acid.
- B) C2H5COOH (Acetic Acid) is already an acid, and its conjugate base is C2H5COO⁻ (acetate ion).
- C) C2H5OH (Ethanol) is also an alcohol, and its conjugate base is C2H5O⁻ (ethoxide ion).
- D) H2O (Water) can act as both an acid and a base, and its conjugate base is OH⁻ (hydroxide ion).

3. **Analyze the Strength of Conjugate Acids**:
- The strength of the conjugate acids can be determined based on their ability to donate protons (H⁺):
- C2H5COOH (Acetic Acid) is a weak acid.
- C2H5OH (Ethanol) is a weaker acid than acetic acid.
- H2O (Water) is a very weak acid.
- C2H6 (Ethane) does not act as an acid.

4. **Identify the Strongest Base**:
- The conjugate base of C2H5COOH (acetate ion) is C2H5COO⁻.
- The conjugate base of C2H5OH (ethoxide ion) is C2H5O⁻.
- The conjugate base of H2O (hydroxide ion) is OH⁻.
- Since C2H6 does not have a conjugate base, we focus on the others.

5. **Conclusion**:
- The conjugate base of C2H5OH (ethoxide ion) is stronger than the acetate ion and hydroxide ion because ethanol is a weaker acid compared to acetic acid and water. Therefore, C2H5O⁻ is the strongest base among the options provided.

### Final Answer:
The strongest base among the given options is **C2H5O⁻ (from C2H5OH)**.