Question

Gold has a molar mass of 197 g/mol. (a) How many moles of gold are in a 3.51 g sample of pure gold? (b) How many atoms are in the sample?

Answer 1

SOLUTION::

Gold molar mass = 197 g/ mol

a) to find the amount of mole of 3.51 g sample of pure gold

we know that  

.......................................(1)

THE 0.01782 moles of gold are in a 3.51 g sample of pure gold

ANSWER=0.01782 moles

b) we know that

Number of atoms= moles * Avogadro's number .................(2)

where Avogadro's number = 6.023*2023  mol-1

and for moles of gold sample = 0.01782 moles

put this values on equation (2)

Number of atoms= moles * Avogadro's number

= (0.01782 mol)*(6.023*1023 mol-1)

=   (0.01782 )*(6.023*1023 )

= 1.073*1022

the number of atom of gold in given sample of gold is = 1.073*1022

ANSWER == 1.073*1022