Chrome iron ore (x) was heated with dry `Na_(2)CO_(3)` in the presence of quick lime and air in a furnace. The mixture was extracted with water and filtered. The filtrate was yellow(A) which on adding conc. `H_(2)SO_(4)` turned to orange red. The solution was evaporated and cooled. The crystals of B were obtained. To the crystals in aqueous solution, `NH_(4)Cl` was added. On fractional crystallization, orange red crystals (C ) is formed.
When alkali is added to B, the species formed is

Options

A. `Cr_(2)O_(7)^(2-)`
B. `Cr^(3+)`
C. `CrO_(4)^(2-)`
D. `Cr^(4+)`

Answer

C

Explanation

`Cr_(2)O_(7)^(2-)+2OH^(-)rarr2CrO_(4)^(2-)+H_(2)O`