Question 24 of 31intermediate🔍 AnalyzeShort Answer2 marks

What sorts of informations can you draw from the following reaction? (CN)₂ (g) + 2OH⁻ (aq) → CN⁻ (aq) + CNO⁻ (aq) + H₂O (l)

Correct Answer

The given reaction provides two major pieces of information. First, it is a disproportionation reaction. In (CN)2(CN)_2, the oxidation state of carbon is +3+3. In the products, carbon is simultaneously reduced to an oxidation state of +2+2 in CN−CN^- and oxidized to an oxidation state of +4+4 in CNO−CNO^-. Since the same element is both oxidized and reduced, it is a disproportionation redox reaction.

Second, the reaction of (CN)2(CN)_2 with OH−OH^- is very similar to the reaction of NO2NO_2 with OH−OH^- (2NO2+2OH−→NO2−+NO3−+H2O2NO_2 + 2OH^- \rightarrow NO_2^- + NO_3^- + H_2O) and halogens with alkalis. This indicates that cyanogen, (CN)2(CN)_2, behaves like a halogen and is thus a pseudohalogen.

Exercise: EXERCISES | Q: 7.20 | (Page Page 20)
For More Understanding

Explanation

The question asks for the information drawn from the given reaction. By calculating oxidation states, carbon in (CN)2(CN)_2 (+3) is both oxidized to CNO−CNO^- (+4) and reduced to CN−CN^- (+2), making it a disproportionation reaction. Furthermore, the reaction pattern with hydroxide ions is characteristic of halogens and similar molecules like NO2NO_2, showing that (CN)2(CN)_2 acts as a pseudohalogen.

Solution Steps

  1. Step 1: Calculate the oxidation state of carbon in (CN)2(CN)_2, which is +3+3 (assuming N is −3-3).

  2. Step 2: Calculate the oxidation state of carbon in CN−CN^-, which is +2+2, showing reduction.

  3. Step 3: Calculate the oxidation state of carbon in CNO−CNO^-, which is +4+4, showing oxidation.

  4. Step 4: Conclude that since the same element is both oxidized and reduced, it is a disproportionation reaction.

  5. Step 5: Compare the reaction with similar reactions like 2NO2+2OH−→NO2−+NO3−+H2O2NO_2 + 2OH^- \rightarrow NO_2^- + NO_3^- + H_2O to conclude that (CN)2(CN)_2 behaves as a pseudohalogen.

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