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JEE Main levelSingle correct optionDifficulty 2 of 3sb138

A sample of $16.8 g$ of pure $NaHCO X_{3}$ (molar mass $84 g mo l^{- 1}$ ) is heated until no further change occurs. The loss in mass is:

A $6.2 g$
B $4.4 g$
C $10.6 g$
D $8.4 g$

Answer: A

16.8/84 = 0.2

mol

NaHCO X_{3}

decomposes by

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

losing 1 mol of (

CO X_{2}

+

H X_{2} O

) per 2 mol. Loss

= 0.1 \times (44 + 18) = 6.2

g. Using only

CO X_{2}

would give 4.4 g, which ignores water.

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