Question

Pick out the incorrect statement about `K_(2)Cr_(2)O_(7)`
A. It act as oxidising agent in basic medium
B. It dissolves in alkali to form chromate
C. It oxidizes `FeSO_(4)` solution to `Fe_(2)(SO_(4))_(3)`
D. It is used as cleansing agent for glassware etc. when mixzed with cold conc `H_(2)SO_(4).`

Answer 1

Correct Answer - A
a) It decomposes on heating to a white heat.
`4K_(2) Cr_(2) O_(7)overset(Delta)to 4K_(2) CrO_(4)+2Cr _(2)O _(3)+ 3O_(2)`
b) `underset(("Orange-red"))(K_(2)Cr_(2)O_(7))+ 2KOH to underset(("Yellow"))(2K_(2)CrO_(4))+ H_(2)O`
c) `K_(2) Cr_(2) O_(7)+ underset(("dil))(4H_(2)SO_(4))toK_(2)SO_(4)+ Cr_(2)(SO_(4))_(3) +4H_(2) O +3O`
`(2FeSO_(4) +H_(2)SO_(4) + O to Fe_(2) (SO_(4))_(3)+ +H_(2) Oxx3)/(K_(2) Cr_(2) O_(7)+ 7H_(2) SO_(4)+ 6FeSO_(4)to3Fe_(2)(SO_(4))_(3)+ K_(2)SO_(4)+Cr_(2) (SO_(4))_(3)+ 7H_(2)O)`
d) With cold and concentrated `H_(2)SO_(4),` it forms `CrO_(3),` which forms `H_(2)CrO_(4)` with water, which has cleansing action.
`K_(2) Cr_(2) +2H_(2) SO_(4) to 2Cr O_(3) +2KHSO_(4)+ H_(2)O`