Chemistry NCERT Exemplar Solutions Class 12th Chapter Six

1. Ans:

(a). According to Ellingham diagram, the reaction of CO2 is more feasible at temperatures lower than 710 K and thus it is a better reducing agent below 710 K.

While the reaction of CO is more feasible at temperatures higher than 710 K and thus it is a better reducing agent at above 710 K.

(b). According to the Ellingham diagram, the more negative the Gibbs free energy of a particular reaction the more feasible it is to carry out. Since the oxides are easier to reduce, sulfide ores are converted into oxides before reduction.

(c). To extract copper, its sulfide ores are supposed to be heated in a reverberatory furnace. The sulfide ore may contain iron as an impurity. So, it is mixed with silica before heating. The oxide of iron slags off as iron silicate. In other words, the iron impurity is removed easily in the form of iron silicate.

(d). Carbon and hydrogen are good reducing agents. They are used preferably for reduction of oxides. They also form escapable gasses as by-products. However, at higher temperatures they form carbides and hydrides. Also, it is not convenient to maintain such high temperatures. Thus, electrolysis is used for this purpose.

(e). Ti is heated in an evacuated vessel along with iodine. Ti forms volatile compounds with iodine. The volatile compound formed decomposes easily. This makes the recovery of the metal convenient. Ti thus fulfills the requirements needed for carrying out vapor phase refining. Hence, this method is used for its purification.