Question

Using the data in Table 3.1, predict whether `Cl_(2)` disproportionates in alkaline solution:
Strategy: Chlorine can exist in manu oxidation states. Chlorine in the `0` oxidation state, as in `Cl_(2)`, can be reduced. Chorine can also be oxidized to one of several positive oxidation states. so `Cl_(2)` can react with itself in a redox reaction, which means that it is possible for chlorine to disproportionate. Search out two different half reactions involving `Cl_(2)`

Answer 1

Solution: For the half reaction
`overset(0)Cl_(2)(g,1"bar")+2e^(-)hArr overset(-1)(2Cl^(-))(aq.)`
Table 3.1 lists `E^(@) = + 1.36`. This large positive reduction potentail shows that `Cl_(2)` can be easily reduced, i.e., it is a realtively powerful oxidizing agent.
The table lists the alf-reaction
`overset(+1)(2ClO^(-))(aq.1M)+2H_(2)O(1)+2e^(-)hArroverset(0)Cl_(2)("g,1 bar")+4OH^(-)(aq. 1M)`
with `E^(@)` of `0.04V`. The reverse of this half-reactions is an oxidation of `Cl_(2)`. When the two half-reaction are combined, the overall reaction is `2Cl_(2)(g,1"bar")+4OH^(-)(aq.,1M)hArrCl^(-)(aq., 1M)+ClO^(-)(aq., 1M)+H_(2)O(1)`
or, more simply
`Cl_(2)(g)+2OH^(-)(aq.,1M)hArr Cl^(-)(aq.,1M)+ClO^(-)(aq.,1M)+H_(2)O(1)`
The standard potential of this reaction is positive : `1.36 V - 0.40 V = 0.96 V`. Therefore, the reaction proceeds spontaneously from left to right. In other words, `Cl_(2)` in unstable in alkaline solution, it is converted to chloride anion and hypochlorite anion.