# Precious metals are commonly measured in troy ounces. A troy ounce is equivalent to 31.1 g. How many moles are in a troy ounce of gold? How many moles are in a troy ounce of platinum? of silver?

Jun 4, 2016

$\text{Number of moles}$ $=$ $\text{Mass"/"Molar Mass}$

#### Explanation:

The number of moles is a numerical unit. One mole of stuff unequivocally specifies $\text{Avogadro's Number}$, ${N}_{A}$, $6.022 \times {10}^{23}$, individual items of that stuff.

Now the molar mass of gold is $196.97 \cdot g \cdot m o {l}^{-} 1$. From where did I get that mass? Did I know it from memory? From where will YOU get it if you are asked to use it?

So $\text{Moles of gold}$ $=$ $\frac{31.1 \cdot g}{196.97 \cdot g \cdot m o {l}^{-} 1}$ $=$ ?? mol

And $\text{Moles of platinum}$ $=$ $\frac{31.1 \cdot g}{195.08 \cdot g \cdot m o {l}^{-} 1}$ $=$ ?? mol.

And $\text{Moles of silver}$ $=$ $\frac{31.1 \cdot g}{107.87 \cdot g \cdot m o {l}^{-} 1}$ $=$ ?? mol.

How do the individual numbers of platinum, silver, and gold compare in these quantities? Which quantity has the greatest monetary value?

On a personal level, I think only a really decadent society would continue to use such an absurd unit as a $\text{troy ounce}$. For God's sake!