Problem 11 - Chemistry: An Atoms-Focused Approach

Question

In an aqueous solution of HF, which compound acts as a Bronsted-Lowry acid and which is the Bronsted-Lowry base?

Step-by-Step Solution

Answer

Answer: In an aqueous solution of HF, the HF molecule acts as a Bronsted-Lowry acid and the water molecule (H2O) acts as a Bronsted-Lowry base.

Step 1: Recall the Bronsted-Lowry Theory

The Bronsted-Lowry theory defines an acid as a substance that can donate a proton (H+) and a base as a substance that can accept a proton. In an aqueous solution, it is common that water molecules act as either a Bronsted-Lowry acid or base.

Step 2: Write the chemical equation for the HF dissociation in water

When HF is added to water, it dissociates and reacts with water molecules. The chemical equation for this process is: HF(aq) + H2O(l) ⇌ H3O+(aq) + F−(aq)

Step 3: Identify the compound that donates a proton

In the equation, HF donates a proton (H+) to a water molecule. This transfer of proton results in the formation of H3O+(aq), which is also called the hydronium ion: HF(aq) → H+ + F− Thus, the HF molecule is the Bronsted-Lowry acid in this aqueous solution.

Step 4: Identify the compound that accepts a proton

In the equation from Step 2, a water molecule (H2O) accepts a proton from HF: H2O(l) + H+ → H3O+ Thus, the water molecule (H2O) is the Bronsted-Lowry base in this aqueous solution.

Step 5: Summarize the results

In an aqueous solution of HF, the compound that acts as a Bronsted-Lowry acid is the HF molecule, and the compound that acts as the Bronsted-Lowry base is the water molecule (H2O).