Question

(A) Deepa has 100 ml of 10.7 % ammonium chloride solution. Vikram added some amount of slaked lime in it. The gas produced in the reaction is allowed to react with 23.85 g of copper (II) oxide to give solid copper.

Calculate :

(i) Write balanced chemical equations for all the reactions involved.

(ii) The amount of slaked lime required to produce sufficient amount of the gas for complete reaction with copper oxide

(iii) The mass of copper after the reaction.

(B)

a to r are elements of the fourth period in the periodic table. Answer the questions given below based on the above information.

(i) Write the formula of the compound formed when o reacts with q.

(ii) Which element forms maximum number of oxidation states ?

(iii) Which element forms a purple salt which is also used as disinfectant and for sterilizing well water.

(iv) Identify the coinage elements in the above period.

(v) Which element is a metalloid ?

(vi) Which of the above elements has the lowest percentage in the common variety of brass ?

Answer 1

(A) Given that

10.7% NH₄Cl in 100 ml solution

So, NH₄Cl = 10.7 gm

(B) As per the fourth period

a

b

c

d

e

f

g

h

i

j

k

k

m

n

o

p

q

r

K

Ca

Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

Ga

Ge

As

Se

Br

Kr

(i) According to above table covalency of o [As] is three and Covolency of q [Br] is one, so compound formed when o reacts with q will be oq3 or AsBr3

(ii) Element g [manganese (Mn)] will show maximum oxidation state (+7).

(iii) Salt of element g [manganese (Mn)] of purple colour will be KMnO₄.

KMnO₄ → Contains two elements of fourth period K and Mn but It shows purple colour and act as a disinfectant and used in sterilizing water due to Mn as Mn is a good oxidising agent.

(iv) Element k [Copper (Cu)] is Coinage metal.)

(v) Element n [Germanium (Ge)] and o [Arsenic (As) ] are metalloids)

(vi) Brass is an alloy made up of copper and zinc [70 : 30 ratio]. So Element l [Zinc (Zn)] has lower percentage (≈ 30%).