A. 10g
B. 25g
C. 20g
D. 15g
Correct Answer:
Option A – 10g
Explanation
Equation: Ca(HCO3)2 → CaCO3 (precipitate) + H2O + CO2 (in the presence of heat)
V = 200 cm³ = 0.2 dm³
C = 0.5 mol/dm³ = 0.5M
N = CV ⟹
N = 0.5 × 0.2 = 0.1 mole
From the equation 1 mole of Ca(HCO3)2 gives 100g of CaCO3
(1 mole CaCO3 = 40 + 12 + (3 x 16) = 100g/m)
0.1 mole of Ca(HCO3)2 gives xg of CaCO3
1/0.10=100/x
x=100×0.10=10g