(A) Consider the reaction
O2− →
O2+O22− This is a redox reaction and to be more specific this is a disproportion reaction because in this case h the oxidation number of oxygen is increasing as well as decreasing at the same time, from −1 to 0 and −2.
(B) The chromate ion has tetrahedral structure with four oxygen atoms around chromium atom; oriented in tetrahedral arrangement.
The dichromate ion consists of two tetrahedral sharing one corner with Cr–O–Cr bond angle of 126°.
(C) This reaction is also a redox reaction, since both reduction and oxidation are involved and also the product formed, that is,
NO3− has a trigonal planar structure.
2MnO4−+5NO2−+6H+ →
Mn2++3H2O+5NO3− (D) This reaction is also a redox reaction since both reduction and oxidation are involved.