Question

'x' grams of calcium carbonate was completely burnt in air. The weight of the solid residue formed is 28 g. What is the value of 'x' in grams ?

• A. 44
• B. 200
• C. 150
• D. 50

Answer 1

Answer: (D)

50

Answer 2

$\underset{\text{1 mol}}{ {CaCO_{3}}} { ->[\Delta] } \underset{\text{1 mol}}{ {CaO}}+CO_{2}$ $=100\,g =40+16$ $=56\,g$ To produce $56\, g$ of residue $(CaO)$, $CaCO_{3}$ needed $=100\,g$ $\therefore$ To produce $28\, g$ of residue, $CaCO_{3}$ needed $=\frac{100}{56}\times28$ $=50\,g$