Question

10 ml of freshly prepared iron sulphate solution was taken in each of four test tubes. Strips of copper, iron, zink and aluminium were introduced, each metal in a different test tube. A black residue was obtained in two of them. The right pair of metals forming the precipitates is:

(a) zinc and aluminium (b) iron and aluminium (c) copper and zinc (d) aluminium and copper

Class XIII.

Answer 1

Cu+feso4 gives no reaction. Fe+feso4 gives. ". Zn+feso4 gives znso4+ Fe. Al+feso4gives also4+Fe. Therefore zinc and al

Answer 2

Answer: The correct answer is Option a.

Explanation:

Single displacement reactions are defined as the reactions in which more reactive metal displaces the less reactive metal from its chemical reaction. The reactivity of metal is given by a series known as reactivity series.

In this series, the metals lying above are more reactive than the metals which lie below. General equation for these reactions follows:

$A+BC\rightarrow AC+B$

A is more reactive metal than B.

According to the question:

We are given 10 mL of freshly prepared solution taken in 4 different test tubes and in each test tube a strip of Copper, Iron, Zinc and Aluminium are put.

Test tubes having aluminium and zinc metal strip will obtain a black residue of iron because these two metals are more reactive than iron and will easily displace iron from its chemical reaction.

Equations for the reaction follows:

$3FeSO_4(aq.)+2Al(s)\rightarrow Al_2(SO_4)_3(aq.)+3Fe(s)\\FeSO_4(aq.)+Zn(s)\rightarrow ZnSO_4(aq.)+Fe(s)\\FeSO_4(aq.)+Fe(s)\rightarrow \text{No reaction}\\FeSO_4(aq.)+Cu(s)\rightarrow \text{No reaction}$

Hence, the correct answer is Option a.