Question

Which of the following are basic oxides? $Mn_2O_7$, $V_2O_3$, $V_2O_5$, $CrO$, $Cr_2O_3$

• A. $Mn_2O_7$ and $V_2O_3$
• B. $V_2O_3$ and $CrO$
• C. $CrO$ and $Cr_2O_3$
• D. $V_2O_5$ and $V_2O_3$

Answer 1

Answer: (B)

$V_2O_3$ and $CrO$

Answer 2

In case of transition metal oxides, the oxides with metals in lower oxidation states are basic in nature. $O.S.$ of $Mn$ in $Mn_2O_7 = +7$; $V$ in $V_2O_3 = +3$; $V$ in $V_2O_5 = +5$; $Cr$ in $CrO = +2$; $Cr$ in $Cr_2O_3 = +3$ Thus in $V_2O_3$, $CrO$ and $Cr_2O_3$ transition metal ion is in lower oxidation state but $Cr_2O_3$ is amphoteric in nature. Hence $V_2O_3$ and $CrO$ are basic in nature.