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SSC CPO 2022 PYQ — Question 52

SSC CPO - 10 Nov 2022 - Shift 2 • General Awareness • Q52

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Which of the following statement is correct?
I. On combustion in excess of air, lithium forms mainly the oxide.
II. The alkali metal halides are all high melting, colourless crystalline liquids.
 

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Correct answer: C

Explanation

The correct answer is Option 3 i.e. Only I.

On combustion in excess of air, lithium forms mainly the oxide, Li2O,  (plus some peroxide Li2​​​​​​O2), sodium forms the peroxide, Na2​​​​​​O2 (and some superoxide NaO2)  whilst potassium, rubidium and caesium form the superoxides, MO2.

Under appropriate conditions pure compounds M2O, M2​​​​​​O2,  and MO2 may be prepared.

Alkali metal halides are indeed colorless crystalline solids, not liquids, at room temperature.

However, their melting points vary.

For instance, lithium fluoride (LiF) has a high melting point, but other alkali metal halides like sodium chloride (NaCl) and potassium bromide (KBr) have lower melting points compared to lithium fluoride.