Question

When 23.8 g of a group 1 carbonate was heated strongly, it decomposed to form the oxide of the group 1 element (call it element X) and 2.70 L of carbon dioxide gas, collected at 25*C. The density of carbon dioxide gas at that temperature was 1.20 g/L. Determine the quantity of the metal , X, and write the balanced equation for the reaction.

Answer 1

The equation of decomposition is:

$X_2CO_3\to X_2O+CO_2$

Mass of $CO_2$ formed$=1.20\frac{g}{L}\times2.70L=3.24g$

Moles of $CO_2$ formed$=\frac{3.24g}{44\frac{g}{mol}}=0.0736mol$

Molar mass of $X_2CO_3=\frac{23.8g}{0.0736mol}=323.369\frac{g}{mol}$

So atomic mass of $X=\frac{323.369-60}{2}=131.6845amu$

Hence quantity of metal $X=131.6845\times0.0736=9.69g$