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Difficulty: Very hardHalogens: Chlorine, Hydrogen Chloride, and Oxoacids

Match each chlorine oxoacid or oxoanion listed in Column I with its corresponding oxidation state, IUPAC designation, or chemical property in Column II.

  • Hypochlorous acid (HClO\text{HClO})A weak, unstable acid with chlorine in the +1+1 oxidation state that decomposes in sunlight to release oxygen gas.
  • Chloric(V) acid (HClO3\text{HClO}_3)A strong oxidizing acid containing chlorine in the +5+5 oxidation state, prepared by reacting barium chlorate with dilute tetraoxosulfate(VI) acid.
  • Perchloric acid (HClO4\text{HClO}_4)The strongest oxoacid of chlorine, exhibiting the highest oxidation state of +7+7.
  • Oxochlorate(I) anion (ClO−\text{ClO}^-)The active bleaching species formed as a conjugate base when chlorine gas reacts with cold aqueous sodium hydroxide.

Answer

Hypochlorous acid (HClO) matches with the weak, unstable acid (+1 oxidation state) decomposing in sunlight to release O2 gas; Chloric(V) acid (HClO3) matches with the strong oxidizing acid (+5 oxidation state) prepared from barium chlorate and dilute H2SO4; Perchloric acid (HClO4) matches with the strongest oxoacid (+7 oxidation state); Oxochlorate(I) anion (ClO-) matches with the active bleaching conjugate base formed in cold aqueous NaOH.
Each chlorine species is accurately paired according to oxidation state calculations, resonance stability of conjugate bases, and established laboratory synthesis routes.

Step-by-Step Solution

1
Determine the oxidation state of chlorine in each specified oxoacid and oxoanion species
In HClO\text{HClO}, chlorine is +1+1. In HClO3\text{HClO}_3, chlorine is +5+5. In HClO4\text{HClO}_4, chlorine is +7+7. In ClO−\text{ClO}^-, chlorine is +1+1.
Oxidation numbers dictate IUPAC nomenclature and help categorize chemical reactivity.
2
Analyze acid strength trends among chlorine oxoacids
Acid strength increases with increasing number of terminal oxygen atoms: HClO<HClO2<HClO3<HClO4\text{HClO} < \text{HClO}_2 < \text{HClO}_3 < \text{HClO}_4. Thus, HClO4\text{HClO}_4 is the strongest oxoacid.
Electronegative terminal oxygen atoms withdraw electron density from the O-H\text{O-H} bond, stabilizing the conjugate base via resonance.
3
Correlate specific preparation methods and stability characteristics to their respective species
HClO\text{HClO} decomposes into HCl\text{HCl} and O2\text{O}_2. HClO3\text{HClO}_3 is synthesized via Ba(ClO3)2+H2SO4→BaSO4↓+2HClO3\text{Ba(ClO}_3)_2 + \text{H}_2\text{SO}_4 \rightarrow \text{BaSO}_4\downarrow + 2\text{HClO}_3. ClO−\text{ClO}^- is generated in cold alkaline chlorination: Cl2+2OH−→ClO−+Cl−+H2O\text{Cl}_2 + 2\text{OH}^- \rightarrow \text{ClO}^- + \text{Cl}^- + \text{H}_2\text{O}.
Matching unique reaction mechanisms and industrial/laboratory preparation routes identifies each chlorine compound.

Key Concept

Oxoacids of chlorine, oxidation states, relative acid strengths, and chemical preparation methods.
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Topics

Halogens: Chlorine, Hydrogen Chloride, and Oxoacids

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