Ncert Exercises & Solutions

Explain the following

1. ${CO}_{2}$ is a better reducing agent below 710 K whereas CO is a better reducing agent above 710 K.

2. Generally sulphide ores are converted into oxides before reduction.

3. Silica is added to the sulphide ore of copper in the reverberatory furnace.

4. Carbon and hydrogen are not used as reducing agents at high temperatures.

5. Vapour phase refining method is used for the purification of Ti.

NEETprep Answer:

(a) As shown in Ellingharn diagram which relates Gibbs free energy and temperature at below 710 K.

∆ G_{(C, {CO}_{2})} < ∆ G_{(C, CO)}

is a better reducing agent than CO while above 710K it becomes a very good reducing agent.

(b) Generally, sulphide ores are converted to oxides before reduction as reduction of oxides can easily be done using C or CO depending upon metal ore and temperature.

FeO + {SiO}_{2} \to \underset{Slag}{{FeSiO}_{3}}

(d) Carbon and hydrogen are not used as reducing agents at high temperature. At high temperature carbon and hydrogen readily form their carbides and hydrides respectively.

(e) Vapour phaserefining methodis used for the purification of Ti as

Ti + 2 I_{2} \overset{523 K}{\to} {TiI}_{4} \overset{1700 K}{\to} Ti + 2 I_{2}

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