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Given that metal oxides such as $Cr_2O_3$ and $Mn_3O_4$ cannot be reduced using Carbon or Carbon monoxide, which of the following must be true?

(1) This is because $Al$ is more electropositive than $Cr$ and $Mn$

(2) This is because $Al$ is more electronegative than $Cr$ and $Mn$

(3) This is because the impurities have lesser affinity for $Al$

(4) None of the above

(a) (4)
(b) (1) and (2)
(c) Only (1)
(d) Only (2)

1 Answer

Ans: (C) Only $(1)$.
Aluminium is used as a reducing agent because it is more electropositive. The oxides of all refractory metals are commercially reduced by Al.
$Cr_2O_3 + 2Al \rightarrow 2Cr + Al_2O_3$
$3Mn_3O_4 + 8Al \rightarrow 4Al_2O_3 + 9Mn$
answered Mar 16, 2014 by balaji.thirumalai
edited Mar 9, 2016 by sharmaaparna1

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