Which of the following is//are false?

Options

A. `Na_(2)Cr_(2)O_(7)` is used as a primary standard in volumetric analysis.
B. Potassium permanganate in excess on treatment with conc. `H_(2)SO_(4)` form manganese heptoxide
C. phosphine, arsine and stibine all precipitates silver from silver nitrate.
D. From Kipp's apparatus waste ferric sulphate and ferrous sulphate mixture is obtained when air or oxygen is passed for longer time.

Answer

A

Explanation

(A) `Na_(2)Cr_(2)O_(7)` is not used as primary standard because it is hydroscopic in nature.
(B) `2KMnO_(4)+3H_(2)SO_(4)+(MnO_(3))_(2)SO_(4)+2H_(2)O`
`(MnO_(3))_(2)SO_(4)+H_(2)O to Mn_(2)O_(7)+H_(2)SO_(4)`
(C ) `PH_(3)+6AgNO_(3)+3H_(2)O to 6Ag+6HNO_(3)+H_(3)PO_(3)`
`AsH_(3)+6AgNO_(3)+33H_(2)O to 6Ag+6HNO_(3)+H_(3)AsO_(3)`
(D) `3FeS_(2)+2H_(2)O+11O_(2) to 2FeSO_(4)+Fe_(2)(SO_(4))_(3)+2H_(2)SO_(4)`