Question

Which of the following oxides cannot be reduced to metal by carbon?

• A. $ZnO$
• B. $A{l}_2{O}_3$
• C. $CuO$
• D. $CaO$

Answer 1

Answer: (B), (D)

The correct options are
B $A{l}_2{O}_3$
D $CaO$

Generally carbon is more reactive than $Zn$ and $Cu$. Hence, $ZnO$ and $CuO$ can be reduced by carbon leading to the formation of corresponding metals, but carbon is less reactive than $Ca$ and $Al$, so $CaO$ and $A{l}_2{O}_3$ can not be reduced by carbon .