When chlorine gas is passed through a hot solution of \(NaOH\), a disproportionation reaction occurs. The zero oxidation state of chlorine changes to:
A. 0 to +5
B. 0 to -1
C. 0 to +3
D. 0 to +1
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is option 3. A, B only.
When chlorine gas \((Cl_2)\) is passed through a hot, concentrated solution of sodium hydroxide \((NaOH)\), a disproportionation reaction occurs. In this reaction, the same element (chlorine) undergoes both oxidation and reduction, resulting in different oxidation states in the products.
Disproportionation Reaction:
The reaction between chlorine gas and hot, concentrated \(NaOH\) can be represented as follows:
\(3Cl_2 + 6NaOH \rightarrow 5NaCl + NaClO_3 + 3H_2O\)
Oxidation States of Chlorine:
Chlorine in \(Cl_2\): Initially, chlorine is in the elemental form \((Cl_2)\) where it has an oxidation state of 0.
Chlorine in \(NaCl\): In sodium chloride \((NaCl)\), chlorine has an oxidation state of -1. This indicates that chlorine has been reduced from \(0\) to \(-1\).
Chlorine in \(NaClO_3\): In sodium chlorate \((NaClO_3)\), chlorine has an oxidation state of +5. This indicates that chlorine has been oxidized from \(0\) to \(+5\).
Analysis of the Changes:
Reduction: Chlorine is reduced from an oxidation state of 0 (in \(Cl_2\)) to -1 (in \(NaCl\)).
Oxidation: Chlorine is oxidized from an oxidation state of 0 (in \(Cl_2\)) to +5 (in \(NaClO_3\)).
Conclusion: In the disproportionation reaction of chlorine with hot, concentrated sodium hydroxide, the chlorine undergoes a change in oxidation state from 0 to both -1 and +5.
The correct changes in oxidation state are from 0 to -1 and 0 to +5, which correspond to A and B.
Thus, the correct answer is option 3: A, B only.