Explain the following :
(a) CO is a better reducing agent below 983 K whereas C is a better reducing agent above 983 K
(b)Generally sulphide ores are converted into oxides before reduction
(c ) Silica is added to the sulphide ore of copper in the reverberatory furnace
(d) Carbon and hydrogen are not used as reucing agents at high temperatures.
(e) Vapour phase refining method is used for the purification of Ti.

Explanation

(c ) Sulphide ore of copper contains iron as impurity. Silica is added to remove this impurity as iron silicate (slag).
` " " underset ("Impurity")(FeO) + SiO _ 2 to underset ("Iron silicate (slag)")(FeSiO_3) `
(d) The reason being that carbo and hydrogen react with metals at high temperature forming their carbides and hybrides respectively.
(e) Ti reacts with iodine at 523 K to form volatile ` TiI_4 ` which decomposes at high temperature (1700 K ) to form pure titanium.