Weight of substance	Weight of CaO produced on heating
A) $100{\text{ g of CaCO}}_3$	1) 42 g
B) ${\text{25 g of CaCO}}_3$	2) 28 g
C) ${\text{50 g of CaCO}}_3$	3) 56 g
D) ${\text{75 g of CaCO}}_3$	4) 14 g

${\text{CaCO}}_{\text{3}}\to {\text{ CaO + CO}}_2$

${\text{1 mole of CaCO}}_3\text{ ----- 1 mole of CaO}$

${\text{100g CaCO}}_3\text{ ----- 56g of CaO}$

${\text{50g of CaCO}}_3\text{ ----- }\frac{56}{2}=28\text{ of CaO}$

${\text{25g of CaCO}}_3\text{ ----- }\frac{56}{4}=14g\text{ of CaO}$

${\text{75g of CaCO}}_3\text{ ----- }\frac{56\times 3}{4}=14\times 3=42g\text{ of CaO}$