Question

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

Answer 1

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