The amount of calcium oxide obtained by heating 25kg of calcium carbonate (80% pure) is

Given weight of calcium carbonate $=25kg=25000g$

$CaC{O}_3\to CaO+C{O}_2$

$100g56g44g$

100g of CaCO3 produces 56g of purity of $CaC{O}_3=80\%$

So, actual weight of $CaC{O}_3=\frac{80}{100}\times 25000=20000g$

Therefore, 20000g of calcium carbonate will produce calcium oxide

$=\frac{56}{100}\times 20000=11200gor11.2kg$ .