Question

Sesquioxides $\left(M_2{O}_3\right)$ of alkali metals:

• A. have been prepared by careful thermal decomposition of $M{O}_2$
• B. are prepared as dark-coloured paramagnetic powder
• C. are colourless diamagnetic substances
• D. are coloured diamagnetic substances

Answer 1

Answer: (A), (B)

The correct options are
A have been prepared by careful thermal decomposition of $M{O}_2$
B are prepared as dark-coloured paramagnetic powder

Sesquioxides $M_2{O}_3$ of alkali metals have been prepared as dark-coloured paramagnetic powders by careful thermal decomposition of $M{O}_2$ ($Rb,Cs,K$).

They can also be obtained by oxidation of liquid ammonia solution of the metals or by controlled oxidation of the peroxides, and are considered to be peroxide disuperoxides $\left[\right(M^{+}{)}_4\left(O_2^{2-}\right)\left(O_2^{-}{)}_2\right]$.

Hence, option A and B are correct.