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JEE Main levelOne or more correct optionsDifficulty 2 of 3sb195

Which of the following statements about washing soda, $Na X_{2} CO X_{3} \cdot 10 H X_{2} O$ , are correct?

AIt decomposes to $Na X_{2} O$ and $CO X_{2}$ on heating to 400 K.
BIt effloresces in dry air.
CIts aqueous solution is alkaline.
DIt can remove permanent hardness caused by dissolved calcium salts.

Answer: B, C, D

The decahydrate loses water in dry air (efflorescence). Carbonate hydrolysis makes the solution alkaline, and carbonate precipitates

Ca X^{2 +}

as

CaCO X_{3}

. Sodium carbonate does not decompose at 400 K; only water is lost on heating.

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