Question

A s-block element (M) reacts with oxygen to form an oxide of the formula MO₂. The oxide is pale yellow in colour and paramagnetic. The element (M) is ______.

पर्याय

• Na

• K

• Ca

• Mg

Answer 1

A s-block element (M) reacts with oxygen to form an oxide of the formula MO₂. The oxide is pale yellow in colour and paramagnetic. The element (M) is K.

Explanation:

When heated, magnesium combines with airborne oxygen to form white magnesium oxide or MgO₂. Its natural state is diamagnetic.

\[\ce{2Mg + O2 -> 2MgO (Diamagnetic)}\]

When sodium burns in air, it produces bright, white light and it produces white coloured sodium oxide. It is diamagnetic in nature.

\[\ce{2Na + O2 -> Na2O (Diamagnetic)}\]

When sodium combines with too much oxygen, sodium peroxide is produced. It is yellow in colour and diamagnetic in nature.

\[\ce{2Na + O2 (excess) -> Na2O2 (Diamagnetic)}\]

When calcium is exposed to air, calcium oxide is grayish-white formed. Its natural state is diamagnetic.

\[\ce{2Ca + O2 -> 2CaO (Diamagnetic)}\]

The white or off-white coloured calcium peroxide is obtained by a reaction between Ca and oxygen. It is diamagnetic in nature.

\[\ce{Ca + O2 -> CaO2 (Diamagnetic)}\]

Burning molten potassium in oxygen produces potassium superoxide. It is pale yellow in colour. It is paramagnetic by nature since it has unpaired electrons.

\[\ce{K + O2(excess) -> KO2 (Paramagnetic)}\]