Q21 of 26 Page 1

Write the role of

(i) I2 in the van Arkel method of refining.


(ii) Cryolite in the extraction of aluminium.


(iii) Dilute NaCN in the extraction of silver.


(i) The impure Zr or Ti is heated in an evacuated vessel with I2 so that all oxygen and nitrogen present in the form of impurities are removed.


Zr + 2I2→ ZrI4


The metal iodide is decomposed on a tungsten filament heated to 1800 K and the pure metal gets deposited on filament.


ZrI4 → Zr + 2I2


(ii) The purified alumina is mixed with cryolite to reduce the melting point and to increase the fusibility.


(iii) Impure silver is leached out with NaCN in presence of air to form a complex. From the complex pure metal is recovered by displacement using Zn.


4Ag + 8CN- +2H2O + O2→ 4[Ag(CN)2]- + 4OH-


2[Ag(CN)2]- + Zn → 2Ag + [Zn(CN)4]2-


More from this chapter

All 26 →
19

(i) Draw the pyranose structure of glucose.

(ii) What type of linkage is present in proteins?


(iii) Give one example each for water-soluble vitamins and fat-soluble vitamins.


 20

(a) For the complex [Fe(CO)5], write the hybridization, magnetic character and spin of the complex. (At. number: Fe = 26)

(b) Define crystal field splitting energy.


 22

Write the major product(s) in the following reactions:


 23

Due to hectic and busy schedule, Mr. Awasthi made his life full of tensions and anxiety. He started taking sleeping pills to overcome the depression without consulting the doctor. Mr. Roy, a close friend of Mr. Awasthi, advised him to stop taking sleeping pills and suggested to change his lifestyle by doing Yoga, meditation and some physical exercise. Mr. Awasthi followed his friend’s advice and after few days he started feeling better.

After reading the above passage, answer the following:


(i) What are the values (at least two) displayed by Mr. Roy?


(ii) Why it is not advisable to take sleeping pills without consulting doctor?


(iii) What are tranquilizers? Give two examples.