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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3sb155

Select the correct statement(s) about alkali metal carbonates and hydrogencarbonates.

A $Li X_{2} CO X_{3}$ decomposes to $Li X_{2} O$ and $CO X_{2}$ on heating.
BSolid $NaHCO X_{3}$ on heating gives $Na X_{2} O$ , $CO X_{2}$ and $H X_{2} O$ .
CAll alkali metal hydrogencarbonates other than that of lithium are known as solids.
D $Na X_{2} CO X_{3}$ and $K X_{2} CO X_{3}$ melt without decomposing on ordinary heating.

Answer: A, C, D

Strongly polarising

Li X^{+}

makes

Li X_{2} CO X_{3}

decompose and

LiHCO X_{3}

non-isolable, whereas Na and K carbonates are stable to heat.

NaHCO X_{3}

decomposes only as far as the carbonate:

2 NaHCO X_{3} Na X_{2} CO X_{3} + CO X_{2} + H X_{2} O

, not to the oxide. Hence three statements are correct.

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