Select the incorrect statement(s):

Options

A. In `K_(2)MnO_(4)` and `CrO_(2)Cl_(2)` the central transition metals/ions have same oxidation state.
B. Both sodium and potassium dichromate can be used as primary standard in volumetric estimations.
C. Potassium dichromate on strong heating evolves oxygen gas and forms green powder.
D. Potassium dichromate on strong heating evolves oxygen gas forms green powder.

Answer

B, D

Explanation

(A) In both compounds central metals have +6 oxidaiton states.
`MnO_(4)^(2-),x+4(-2)=-2,` So, `x=6` , `CrO_(2)Cl_(2)," "x+2(-2)+2(-1)=0,` so `x=6`
(B) Sodium dichromate is `Na_(2)Cr_(2)O_(7).2H_(2)O`, so it can not be weighed correctly for the preparation of standard solutions.
(C) `2K_(2)Cr_(2)O_(7)overset(Delta)to2K_(2)CrO_(4)+Cr_(2)O_(3)("green")+3//2O_(2)`.
(D) `4KMnO_(4)+4KOHoverset(Delta)to4K_(2)MnO_(4)("green")+2H_(2)O+O_(2)`.