A student took four test tubes I, II, III, and IV containing aluminium sulphate, copper sulphate, ferrous sulphate and zinc sulphate solution respectively. He placed an iron strip in each of them. He found a brown deposit formed in test tube (1) I (2) II (3) III (4) IV



 Answer: (2) Iron (Fe) is more reactive than copper (Cu). Hence, Fe can displace Cu from copper sulphate solution to produce iron sulphate and a brown deposit of copper. On the other hand, aluminium (Al) and zinc (Zn) are more reactive than Fe. Therefore, Fe cannot displace Al and Zn from aluminium sulphate and zinc sulphate solutions. Hence, the student will observe a brown deposit in test tube II.