Acidity of acetylene, water and ammonia decreases in the order _______

Answer

To determine the order of acidity for acetylene (C2H2), water (H2O), and ammonia (NH3), we can analyze their structures and hybridization:

### Step 1: Understand Acidity
Acidity refers to the ability of a compound to donate a proton (H+). The stronger the acid, the more readily it donates a proton.

### Step 2: Analyze the Structure and Hybridization
1. **Acetylene (C2H2)**:
- Structure: H-C≡C-H (triple bond between carbon atoms).
- Hybridization: The carbon atoms in acetylene are sp hybridized, which means they have 50% s character and 50% p character.
- Acidity: The sp hybridized carbon has a stronger hold on its electrons, making the hydrogen atoms more acidic.

2. **Water (H2O)**:
- Structure: H-O-H.
- Hybridization: The oxygen in water is sp3 hybridized, giving it 25% s character and 75% p character.
- Acidity: Water can donate a proton, but it is less acidic than acetylene due to the lower s character.

3. **Ammonia (NH3)**:
- Structure: H-N-H (with a lone pair on nitrogen).
- Hybridization: The nitrogen in ammonia is also sp3 hybridized, similar to water, with 25% s character and 75% p character.
- Acidity: Ammonia is less acidic than water since it tends to act more as a base (accepting protons) rather than donating them.

### Step 3: Compare Acidity
- Acetylene (sp hybridized) has the highest acidity due to its higher s character.
- Water (sp3 hybridized) is next, as it can donate protons but is less acidic than acetylene.
- Ammonia (also sp3 hybridized) is the least acidic, as it primarily acts as a base.

### Conclusion
The order of acidity from highest to lowest is:
**Acetylene > Water > Ammonia**

### Final Answer
Acidity of acetylene, water, and ammonia decreases in the order: **Acetylene > Water > Ammonia**.

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