Question

Mass of one atom of an element is 6.645 x 10⁻²³ g. How many moles of element are there in 0.320 kg.

Answer 1

Given conditions ⇒

Mass of the 1 atom of the element = 6.645 × 10⁻²³ g.
No. of atoms = 1.

Using the Formula,
No. of atoms = Mass/Atomic mass × Avo. Number.

1 = (6.645 × 10⁻²³)/Atomic Mass × 6.022 × 10²³

∴ Atomic Mass = 6.645 × 6.022
  = 40.01619 g.
  = 40.02 g.
  ≈ 40 g.

Now, 
Mass = 0.320 kg.
 = 320 g.

∵ No. of moles = Mass/Atomic Mass.
   = 320/40.
   = 8 moles.


Hence the number of moles of atoms is 8 .



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