question_answer 64)

  A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present in one gram of this sample of gold?

Answer:

  Let, the mass of the sample is 100 g            Mass of gold = 90 g and         mass of copper =(100-90)= 10 g 100 g of sample has gold = 90 g  1 g of this sample has gold   Atomic mass of gold (Au) = 197 g 197 g of gold have number of atoms 0.9 g of gold will have number of atoms