Question

92 g mixture of $CaC{O}_3$ and $MgC{O}_3$ heated strongly in an open vessel. After complete decomposition of the carbonates it was found that the weight of residue left behind is 48 g. Find the mass of $MgC{O}_3$ in grams in the mixture.

Answer 1

$CaC{O}_3\left(s\right)+MgC{O}_3\left(s\right)\underset{}{\overset{\Delta }{\to }}CaO\left(s\right)+MgO\left(s\right)+2C{O}_2\left(g\right)$

Thus on Reaction of $1$ mole of $CaC{O}_3$ & $1$ mole of $MgC{O}_3$, the residue left is $14$ mole of $CaO$ & $1$ mole of $MgO$

Molecular wt of $CaC{O}_3=100g$ $MW$ of $MgC{O}_3=84g$

$M$ wt of $CaO=56gMW$ of $MgO=40g$

Thus when a mixture of $184g$ is heated, residue weight $96g$

Also, when a mixture of $92g$ is heated, residue weight $48g$

A mixture of contains $84gMgC{O}_3$

$\therefore$ A mixture of $92g$ contains $42gMgC{O}_3$