A 18.4 g mixture of CaCO3 and MgCO3 is heated strongly until both carbonates decompose completely to the oxide and CO2. The CO2 evolved measures 4.48 L at STP (Ca = 40, Mg = 24, C = 12, O = 16; 22.4 L mol^-1). The mass of CaCO3 in the mixture is:

JEE Advanced levelSingle correct optionDifficulty 3 of 3mc049

A $18.4 g$ mixture of $CaCO X_{3}$ and $MgCO X_{3}$ is heated strongly until both carbonates decompose completely to the oxide and $CO X_{2}$ . The $CO X_{2}$ evolved measures $4.48 L$ at STP (Ca = 40, Mg = 24, C = 12, O = 16; $22.4 L mo l^{- 1}$ ). The mass of $CaCO X_{3}$ in the mixture is:

Each carbonate gives

1

mol

CO X_{2}

per mole, so

x + y = 4.48/22.4 = 0.200

. Masses:

100 x + 84 y = 18.4

. Substituting,

16 x = 18.4 - 16.8 = 1.6

, so

x = 0.10

mol and the mass of

CaCO X_{3}

= 10.0 g