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 = 6.022×1023 atoms
32 moles of sulphur = 6.022×1023 ×32 = 192.7×1023 atoms
b) 32 g of sulphur
32 g of sulphur contains = 6.022×1023 atoms
c) 32 u of sulphur
32 u of sulphur contains = 6.022×1023 atoms

2) a) 280 g of silicon
Molar mass of silicon = 28 g
Number of moles (n) = Given massMolar mass
n = 28028 = 10 moles
b) 12.044×1025 atoms of phosphorus
6.022×1023 atoms = 1 mole of phosphorus
12.044×1025 atoms = 16.022×1023×12.044×1025 = 2×102 moles
c) 19 atoms of flourine
6.022×1023 atoms = 1 mole of flourine atom
19 atoms of flourine = 16.022×1023×19  = 3.15×10-23 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

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