chem
posted by tiffany .
How many gold atoms are in an 0.408 ounce, 18 gold bracelet? (18 gold is 75% gold by mass.)

Steps are
0.408 oz x 0.75 give masss of gold
convert the mass in oz to mass in g (say =X)
Look up molar mass for gold (say =M)
number of moles of gold is then
X/M
If Avogadro's Number =N (number of atoms per mole)
then the number of atoms is
XN/M