Question

A gold sample contains 90% of gold and rest copper. How many atoms of gold are present in one gram of this sample of gold. (Au = 197 u).

Answer 1

Dear Student

As gold is 90% pure. 1 gram of it will have 0.9 g gold actually.

As atomic mass of gold is 197 u

So, 197 g contain 6.022 x 10²³ atoms
0.9 g will contain = (6.022 x 10²³ * 0.9)/197 = 0.0275 x 10²³ or 2.75 x 10²¹ atoms

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