Question

calculate the number of moles in
1. 16g of calcium.
2. 3.011* 10 to the power of 23

Answer 1

1) 16 g of calcium
Given mass = 16 g
Molar mass = 40 g mol^-1
Number of moles (n) = $\frac{\text{Given mass}}{\text{Molar mass}}$
n = $\frac{16}{40}$ = 0.4 moles

2) 3.011$\times$10²³ particles
n = $\frac{\text{Number of particles}}{\text{Avagadro number}}$

n = $\frac{3.011\times {10}^{23}}{6.022\times {10}^{23}}$ = 0.5 moles