Write the chemical reaction for chlorous acid in water, whoseequilibrium constant is aK a . Include the physicalstates for each species. aK a reaction:
A) {HClO}_2 (aq) ⇌ H^+ (aq) +ClO_2^- (aq)
B) HClO2)⇌H++ClO2−)HClO 2 (l)⇌H + (aq)+ClO 2− (aq)
C) HClO2)⇌H+()+ClO2−(HClO 2 (aq)⇌H +(aq)+ClO 2− (l)
D) HClO2()⇌)+ClO2−)HClO 2 (l)⇌H + (l)+ClO 2− (aq)
The Correct Answer and Explanation is:
The correct chemical reaction for chlorous acid in water, along with the proper physical states for each species, is:
A) ( \text{HClO}_2(aq) \rightleftharpoons \text{H}^+(aq) + \text{ClO}_2^-(aq) )
Explanation
Chlorous acid (HClO₂) is a weak acid that partially dissociates in aqueous solution. In this dissociation reaction, HClO₂ donates a proton (H⁺) to form its conjugate base, chlorite ion (ClO₂⁻). This process can be represented by the equilibrium equation as follows:
[
\text{HClO}_2(aq) \rightleftharpoons \text{H}^+(aq) + \text{ClO}_2^-(aq)
]
Physical States:
- HClO₂(aq): The subscript (aq) denotes that chlorous acid is dissolved in water, making it an aqueous solution. It is important to note that HClO₂ is not a solid or gas under these conditions.
- H⁺(aq): The hydrogen ion (proton) is also in aqueous solution, meaning it is present in water and contributes to the acidity of the solution.
- ClO₂⁻(aq): The chlorite ion is likewise in aqueous solution, indicating that it is produced when HClO₂ dissociates.
Why Other Options Are Incorrect
- Option B: Incorrect because it states ( \text{HClO}_2 ) is a liquid (l), while it is actually present as an aqueous solution (aq) in water.
- Option C: Incorrect because it also improperly implies that ( \text{HClO}_2 ) exists in a liquid state, and it doesn’t format the ions correctly.
- Option D: Incorrect as it lists ( \text{HClO}_2 ) as a liquid (l), which does not apply when discussing its dissociation in water.
Importance of Equilibrium Constant
The dissociation of chlorous acid in water is characterized by an equilibrium constant, ( K_a ), which quantifies the strength of the acid. A higher ( K_a ) value indicates a stronger acid that dissociates more completely in solution, while a lower ( K_a ) signifies weaker acidity. Understanding the dissociation of weak acids like chlorous acid is fundamental in chemistry as it impacts pH levels, chemical reactivity, and the behavior of solutions in various biological and chemical processes.