Question

calculate the number of particles in each of the following :

1) 48 kg of sodium atom Na

2) 8 grams of $O_2$ molecules

Answer 1

1) Molecular mass of Na = 23 g
48kg = 48000g
23 g of sodium(Na) = 1 mole of Na = 6.022 x 10²³ Na atoms/particles.
23 g of Na = 6.022$\times {10}^{23}$ particles
1 g of Na = $\frac{6.022\times {10}^{23}}{23}$
48000 g of sodium will contain = $\frac{6.022\times {10}^{23}\times 48000}{23}$ = $1.2\times {10}^{27}$ atoms
2) 32 g of $O_2$ = 1 mole of $O_2$ molecule = 6.022$\times {10}^{23}{O}_{2}molecule$
1 g of $O_2$ = $\frac{6.022\times {10}^{23}}{32}$
8 g of $O_2$ =$\frac{6.022\times {10}^{23}\times 8}{32}$ = 1.5$\times {10}^{23}$ molecules