Question

Which of the following statements regarding $d-$ block elements are true?

• A. The colour of anhydrous $Cu{SO}_4$ is blue and the colour of hydrated copper sulphate is white.
• B. "splitting of silver" can be prevented by covering the surface of molten silver with charcoal.
• C. Iodine liberated in a reaction can be estimated by titration against a standard thiosulphate solution.
• D. Lanthanum is first element of third transition series.

Answer 1

Answer: (B), (C), (D)

The correct options are
B "splitting of silver" can be prevented by covering the surface of molten silver with charcoal.
C Iodine liberated in a reaction can be estimated by titration against a standard thiosulphate solution.
D Lanthanum is first element of third transition series.

(A)The colour of anhydrous copper sulphate is white whereas the colour of hydrated copper sulphate is blue. Thus option A is not true.
(B) During Spitting of silver, oxygen is absorbed by molten Ag, which is evolved on cooling and the silver particles are scattered.
Silver can dissolve upto 22 times its volume of oxygen.
The spitting of silver can be controlled by the addition of a deoxidant such as charcoal to the molten silver.
This can also be achieved by covering the surface of molten silver with non oxidizing agents or traces of copper, bismuth or zinc.
Thus option B is true.
(C) Iodine liberated in a reaction can be estimated by titration against a standard thiosulphate solution. $I-2+2N{a}_2{S}_2{O}_3\to N{a}_2{S}_4{O}_6+2NaI$. Thus option C is true.
(D) Lanthanum is first element of third transition series. Lutetium is the last element of third transition series. Thus option D is true.