Question

Choose the correct answer form the alternatives given.
Match column I with column II and mark the appropriate choice.

	Column I		Column II
(A)	Li	(i)	$M_2{O}_2$
(B)	Na	(ii)	$M{O}_2$
(C)	Rb	(iii)	$M_{2}O$

• A. $\left(A\right)\to \left(i\right),\left(B\right)\to \left(ii\right),\left(C\right)\to \left(iii\right)$
• B. $\left(A\right)\to \left(iii\right),\left(B\right)\to \left(ii\right),\left(C\right)\to \left(i\right)$
• C. $\left(A\right)\to \left(iii\right),\left(B\right)\to \left(i\right),\left(C\right)\to \left(ii\right)$
• D. $\left(A\right)\to \left(ii\right),\left(B\right)\to \left(iii\right),\left(C\right)\to \left(i\right)$

Answer 1

Answer: (C)

$\left(A\right)\to \left(iii\right),\left(B\right)\to \left(i\right),\left(C\right)\to \left(ii\right)$

The alkali metals tarnish in dry air due to the formation of their oxides which in turn react with moisture to form hydroxides. They burn vigorously in oxygen forming oxides. Lithium forms monoxide ${Li}_{2}O$, sodium forms peroxide ${Na}_2{O}_2$, the other metals form superoxides $O^{2-}$ ions.

$4Li+O_2\to 2{Li}_{2}O$ (normal oxide)

$2Na+O_2\to 2{Na}_2{O}_2$ (peroxide)

$M+O_2\to M{O}_2$ (superoxide)

where M is $M=K,Rb,Cs$