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.
'C' on heating gave

Options

A. `NH_(3)` as a titrant and B as indicator
B. `N_(2)`
C. `NO_(2)`
D. `CO_(2)`

Answer

B

Explanation

`(NH_(4))_(2)Cr_(2)O_(7)rarrN_(2)+4H_(2)O +Cr_(2)O_(3)`