1. how many individual atoms are there in each of the following ? (a) 32 moles of sulphur (b) 32g of sulphur (c) 32u of sulphur (S = 32) 2. how many moles are there in each of the following ? (a) 280g of silicon (b) 12.044 x 10^25 atoms of phosphorus (c) 19.0 atoms of fluorine 3. One mole of zinc atoms weigh 65g. calculate the weight of one atom of zinc.

1) a) 32 moles of sulphur
1 mole of sulphur contains = 6.022$\times$10²³ atoms
32 moles of sulphur = 6.022$\times$10²³ $\times$32 = 192.7$\times$10²³ atoms
b) 32 g of sulphur
32 g of sulphur contains = 6.022$\times$10²³ atoms
c) 32 u of sulphur
32 u of sulphur contains = 6.022$\times$10²³ atoms

2) a) 280 g of silicon
Molar mass of silicon = 28 g
Number of moles (n) = $\frac{\text{Given mass}}{\text{Molar mass}}$
n = $\frac{280}{28}$ = 10 moles
b) 12.044$\times$10²⁵ atoms of phosphorus
6.022$\times$10²³ atoms = 1 mole of phosphorus
12.044$\times {10}^{25}$ atoms = $\frac{1}{6.022\times {10}^{23}}\times 12.044\times {10}^{25}$ = 2$\times$10² moles
c) 19 atoms of flourine
6.022$\times$10²³ atoms = 1 mole of flourine atom
19 atoms of flourine = $\frac{1}{6.022\times {10}^{23}}\times 19$  = 3.15$\times$10^-23 moles

3) 1 mole = 6.022 X 10²³ atoms
6.022 X 10²³ atoms of zinc weigh  = 65 g
1 atom of zinc weighs = 65 / 6.022 X 10²³ = 10.79 X 10²³ g