Solution:
To determine which group of ions/molecules do not undergo disproportionation, we need to understand the concept of a disproportionation reaction. In such a reaction, a single element undergoes simultaneous oxidation and reduction, forming two different products. Essentially, the element starts at a particular oxidation state and splits into products with higher and lower oxidation states.
We can analyze each group and assess if any of the species undergo disproportionation:
Option A:
F2,ClO−,Cl2,ClO2−
- F2 : Fluorine in the F2 molecule does not undergo disproportionation because it cannot have higher oxidation states (typically remains as -1 in compounds, but in F2 it is 0 ).
- ClO−: Hypochlorite can undergo disproportionation:
2ClO−⟶ClO2−+Cl−
- Cl2 : Chlorine gas can undergo disproportionation:
- ClO2−: Chlorite can also undergo disproportionation:
2ClO2−⟶ClO3−+ClO2−(g)
Thus, Option A contains molecules that undergo disproportionation.
Option B:
P4,H2O2,BrO2−,NO2
- P4 : Phosphorus in P4 does not undergo disproportionation under normal conditions.
- H2O2 : Hydrogen peroxide undergoes disproportionation:
2H2O2⟶2H2O+O2
- BrO2−: Bromite ion can undergo disproportionation in acidic conditions:
2BrO2−+4H+⟶BrO3−+Br2+2H2O.
- NO2 : Nitrogen dioxide can disproportionate:
2NO2+H2O⟶HNO3+HNO2
Thus, Option B has molecules that undergo disproportionation.
Option C:
Cr2O72−,F2,MnO4−,ClO4−
- Cr2O72− : Dichromate doesn't undergo disproportionation under normal conditions.
- F2 : As mentioned before, fluorine gas doesn't undergo disproportionation.
- MnO4−: Permanganate ion doesn't undergo disproportionation under normal conditions.
- ClO4−: Perchlorate ion doesn't undergo disproportionation under normal conditions.
Thus, Option C has molecules that do not undergo disproportionation.
Option D:
ClO3−,S8,ClO−,ClO4−
- ClO3−: Chlorate ions can disproportionate in some reactions but less common.
- S8 : Sulfur in S8 does not undergo disproportionation.
- ClO−: As mentioned, hypochlorite undergoes disproportionation.
- ClO4−: Perchlorate ion doesn't undergo disproportionation under normal conditions.
Thus, Option D contains molecules that undergo disproportionation.
The correct choice is Option C : Cr2O72−,F2,MnO4−,ClO4−since none of these species undergo disproportionation.
© examsiri.com