The choice of a reducing agent in a particular case depends on thermodynamic factor. How far do you agree with this statement? Support your opinion with two examples.
Carbon monoxide is more effective agent that carbon below 983 K but above this temperature the reverse is true. How would you explain this?
The value of ΔrG° for formation of Cr2O3 is – 540 kJmol–1 and that of Al2O3 is – 827 kJ mol-1. Is the reduction of Cr2O3 possible with Al?
Predict the modes of occurrence of the following three types of metals:
(i) Highly reactive (e.g., Na)
(ii) Moderately reactive (e.g., Fe)
(iii) Noble metal (e.g., Au)
How do non-metals occur in nature? How are they extracted/isolated from their natural resources?
Some non-metals like inert gases (He, Ne, Ar, Kr, Xe) occur free in nature, whereas some occur in both free and combined states e.g., oxygen, hydrogen, nitrogen, halogens and carbon etc.
Non-metals in general are extracted from their
natural resources by any of the following methods:
(i) By the reduction of oxides and halides.
(ii) By electrolyte reduction of salts, e.g., Cl2 by electrolytic reduction of conc. NaCl solution.
(iii) By the thermal decomposition of their hydrides.
Name the chief ores of tin, iron and aluminium. What methods are employed for the concentration/purification of their ores?
Name three ores which are concentrated by froth-floatation process. What is meant by depressant?
Discuss some of the factors which need consideration before deciding on the method of extraction of metal from its ore.
You are provided with samples of some impure metals such as zinc, copper and germanium. Which methods could you recommend for the purification of each of these metals?