Question

In certain investigatory project one grain of zinc granules were added to each of the four
test tubes A, B, C, D containing water, dilute hydrochloric acid, concentrated caustic
soda solution and blue coloured solution of copper sulphale respectively. The observations
made were as under :
Tube 'A
No reaction in cold or box
(Water)
Tube "B" Vigorous reaction forming a colourless gas hydrogen
(Dil.HCI)
Tube "C" Reaction occurs on heating with the evolution of hydrogen
(Conc. NaOH)
Tube 'D Blue colour of the solution slowly decolourises.
(CuSO4(aq)
Answer the following questions on the basis of above observations:
(a) Write the chemical reaction between zinc and Cuso, solution.
(b) Describe as to how hydrogen is evolved by reaction with hot NaOH.
(c) Which out of copper and zinc is more active metal ?
(d) What is the category of chemical reactions of zinc with HCl and that with Cuso4?
​

Answer 1

Answer:

Observation of student C are correct as Fe cannot displace Zn from its ZnSO

4

solution.On the other hand Zn can displace Fe from FeSO

4

solution to form ZnSO

4

which is colourless and black coloured residue of Fe.The chemical equation for this reaction can be written as:

Zn+FeSO

4

→ZnSO

4

+Fe

Answer 2

Zinc is reactive crystalline metals which reactive with acids, bases and other non-metals.

Explanation:

A) Zinc granules react with copper sulphate and form zinc sulphate. The balanced reaction is $Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$.

B) Sodium hydroxide is a base. The zinc granules react with NaOH to produce sodium zincate along with hydrogen gas. The balanced reaction is $Zn + 2NaOH \xrightarrow{heat} Na_2ZnO_2 + H_2$.

C) The zinc is more reactive than copper because it readily displaced the copper from copper sulphate and form zinc sulphate. During the reaction the blue coloured copper sulphate change into colourless solution.

D) The zinc reaction with copper sulphate and HCl is the example single displacement reaction.