Question

If we added FeSO₄ to above four test tubes, in which test tube we observe black residue? 

1) ‘A’ and ‘B’ 

2) ‘B’ and ‘D’ 

3) ‘B’ and ‘C’ 

4) ‘A’ and ‘C’

Answer 1

2) ‘B’ and ‘D’ 

Based on metal reactivity series (Fe – black ppt)