NCERT 12 Chemistry General Principles and Processes Of Isolation of Elements Chapter 6 Exercise 1

Q.6.1. Suggest a condition under which magnesium could reduce alumina.
Ans. The two redox reactions are :
chemistry chapter 6 ex . 1
chemistry chapter 6 ex . 1.1
Q.6.2. Although thermodynamically feasible, in practice, magnesium metal is not used for the reduction of alumina in the metallurgy of aluminium. Why?
Ans. Below the temperature (1623 K), corresponding to the point of intersection of Al2 O3 and MgO curve in, magnesium can reduce alumina as discussed in. But magnesium is a much costlier metal than  and hence the process will be uneconomical.
Q.6.3. Why is the reduction of a metal oxide easier if the metal formed is in the liquid state at the temperature of reduction?
Or Account for the following fate. The reduction of a metal oxide is easier if the metal is formed in the liquid state at the temperature of reduction.
chemistry chapter 6 ex . 3
Q.6.4. At a site, low grade copper are available and zinc and iron scraps are also available. Which of the two scraps will be more suitable for reducing the leached copper ore and why ?
Ans. The E0 value for the redox couple Zn2+ / Zn2+(-0.76 V) is more negative than of Fe2+ / Fe (-0.44 V) redox couple. Therefore, zinc is more reactive than iron and hence reduction will be faster in case if zinc scraps are sed. But zinc is a costlier metal than iron so using iron scarps would be more economical.
Updated: December 9, 2020 — 2:24 pm

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