A sample contains 4.70×10−4 mol of gold, Au. How many atoms of gold are in the sample?
n = 4.70 x 10-4 mol
The number of atoms of gold, which can be symbolized as
N = ? atoms
N = n x NA
N = n x NA
N = (4.70 x 10-4 mol) x (6.02 x 1023 atoms/mol)
N = 2.8294 x 1020 atoms
N = 2.83 x 1020 atoms (3 significant digits)
There are 2.83 x 1020 atoms of gold in 4.70 x 10-4 mol sample.