Question

which model represents a strong acid?

key
\\(0.20\text{ mol h}^+\\)
\\(0.20\text{ mol a}^-\\)
\\(5.0\text{ l container}\\)

Explanation:

Understand the definition of a strong acid

A strong acid is defined as an acid that dissociates completely in aqueous solution. This means that when a strong acid \(HA\) is dissolved in water, virtually all of the \(HA\) molecules split into their constituent ions:

$$HA ightarrow H^+ + A^-$$

In a particulate model, a strong acid should show only separated \(H^+\) ions (represented by circles) and \(A^-\) ions (represented by squares). There should be no intact \(HA\) molecules (represented by circles attached to squares).

Analyze the particulate representations

Let's examine each of the three containers from left to right:

• Left Container: Most of the particles are shown as circles attached to squares (intact \(HA\) molecules), with only a few separated. This represents a weak acid with a low degree of ionization.
• Middle Container: Again, we see several intact \(HA\) molecules (circles attached to squares) along with some free ions. This also represents a weak acid.
• Right Container: All circles (representing \(H^+\)) and squares (representing \(A^-\)) are completely separated from each other. There are no intact \(HA\) molecules (no circles attached to squares). This represents complete dissociation.

Identify the correct model

Since the rightmost model shows 100% dissociation of the acid molecules into separate \(H^+\) and \(A^-\) ions, it represents a strong acid.

Answer:

• (A) The first model (left)
• (B) The second model (middle)
• (C) The third model (right) (Correct answer)