NaOH is a Bronsted-Lowry base because?
1) it is a polar molecule
2) it can dissolve in water
3) it is a hydroxide donor
4) it is a proton acceptor
The Correct Answer and Explanation is:
The correct answer is: 4) it is a proton acceptor.
Explanation:
The Bronsted-Lowry theory defines acids as proton (H⁺) donors and bases as proton acceptors. This concept revolves around the transfer of protons (hydrogen ions) in a chemical reaction.
Why NaOH is a Bronsted-Lowry Base:
- NaOH Dissociates in Water:
Sodium hydroxide (NaOH) is an ionic compound that dissociates completely in water into sodium ions (Na⁺) and hydroxide ions (OH⁻). The dissociation reaction is:
[
\text{NaOH} \rightarrow \text{Na⁺} + \text{OH⁻}
] - Hydroxide Ion as a Proton Acceptor:
The hydroxide ion (OH⁻) produced during dissociation is highly reactive and has a strong affinity for protons (H⁺). When OH⁻ encounters an H⁺ ion in solution, it readily combines to form water (H₂O). This reaction can be written as:
[
\text{OH⁻} + \text{H⁺} \rightarrow \text{H₂O}
]
Here, OH⁻ acts as a Bronsted-Lowry base because it accepts a proton from an acid.
Why the Other Options Are Incorrect:
- Polar Molecule:
While polarity plays a role in solubility and interactions, being polar does not directly classify a substance as a Bronsted-Lowry base. NaOH is ionic, not molecular. - Dissolution in Water:
The ability to dissolve in water is a physical property and is not directly related to its behavior as a Bronsted-Lowry base. - Hydroxide Donor:
Although NaOH produces hydroxide ions, this is part of its dissociation process, not its classification under the Bronsted-Lowry theory. The key is the ability to accept a proton, not just produce OH⁻.
In summary, NaOH qualifies as a Bronsted-Lowry base because the OH⁻ ions it generates in solution readily accept protons from acids, exemplifying the fundamental definition of a base in this theory.