10.0 g of a mixture of Na2CO3 and NaHCO3 is heated strongly until the mass is constant; the loss in mass is 1.55 g. Only 2NaHCO3 -> Na2CO3 + CO2 + H2O occurs (Na=23, C=12, O=16, H=1). The mass percentage of NaHCO3 in the mixture is

JEE Advanced levelSingle correct optionDifficulty 3 of 3mc153

10.0 g of a mixture of $Na X_{2} CO X_{3}$ and $NaHCO X_{3}$ is heated strongly until the mass is constant; the loss in mass is 1.55 g. Only $2 NaHCO X_{3} Na X_{2} CO X_{3} + CO X_{2} + H X_{2} O$ occurs ( $Na = 23$ , $C = 12$ , $O = 16$ , $H = 1$ ). The mass percentage of $NaHCO X_{3}$ in the mixture is

2 mol

NaHCO X_{3}

(168 g) loses

CO X_{2} + H X_{2} O

= 44 + 18 = 62 g. Mass of

NaHCO X_{3}

= 1.55 x 168/62 = 4.2 g. Percentage = 4.2/10.0 x 100 = 42%. Using only

CO X_{2}

loss would give 29.6%.