calculate the number of particles in the following:
(a)69 g of Na atoms. (b)56 g of He (c) 0.1 mole of atom.

1) Molar mass of sodium atom  = 23 g mol‚Äč-1
23 g of sodium contains = 6.022×1023 particles
69 g of sodium = 6.022×102323×69 = 18.066×1023 particles

2) Molar mass of helium = 4 g mol-1
4 g of He contains = 6.022×1023 particles
56 g of He contains = 6.022×10234×56 = 84.308×1023 particles

3) 1 mole of atom contains = 6.022×1023 particles 
0.1 mole contains = 6.022×1023 ×0.1 = 6.022×1022 particles 
 

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Answer;
A)18.84 X 10*23 atoms.
B) 84.308 X 10*23. Atoms.
C) 6.022 X 10*22 particles.
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answers:
a)18.84 X 10*23 atoms.
b)84.308 X 10*23 atoms.
c)6.022 X 10*22 particles.
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  1. 69/23x6.022x10*23
  2. 56/4x6.022x10*23
  3. 6.022x10*23 particles of that substance
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