Question

How many atoms of calcium are present in 2g of calcium? (Atomic mass of $\mathrm{Ca}$ = 40)

Answer 1

1. No of moles of $\mathrm{Ca}$ = $\frac{2}{40}$= 0.05 moles
2. 1 mole Ca atom = $6.022\times {10}^{23}$ $\mathrm{Ca}$ atoms
3. Therefore, 0.05 moles of $\mathrm{Ca}$ atom = 0.05$\times$$6.022\times {10}^{23}$ = $\mathit{3}\mathit{.}\mathit{01}\mathit{\times }{\mathit{10}}^{\mathit{22}}$ atoms.