Question

Calculate the number of moles in 5g of Calcium carbonate(CaCO₃)?

Answer 1

• The gram molecular mass is defined as the molecular mass of a mole of a substance expressed in grams.
• The relation between gram molecular mass, number of moles, and Avogadro's number is

The molar mass of a substance = 1 mole of that substance = 6.022×10²³ molecules.

• Number of moles of substance (n) = $\frac{\mathrm{Given}\mathrm{weight}\mathrm{of}\mathrm{substance}}{\mathrm{Molecular}\mathrm{weight}\mathrm{of}\mathrm{the}\mathrm{substance}}$

The molecular weight of Calcium carbonate(CaCO₃) = Atomic weight of individual components of Calcium carbonate(CaCO₃).

i.e., Atomic weight of Calcium (Ca) = 40g.

Atomic weight of Carbon(C) = 12 g

Atomic weight of Oxygen (O) = 16, since there are 3 oxygen atoms, Atomic weight = 16 × 3= 48g

Therefore the relative molecular weight of Calcium carbonate(CaCO₃) = 40+12+48 =100g

Given the weight of Calcium carbonate(CaCO₃) = 5g

Therefore Number of moles of Calcium carbonate(CaCO₃)= $\frac{5}{100}$ = 0.05moles.

Thus the number of moles in 5g of Calcium carbonate(CaCO₃)= 0.05moles.