# 14 carat gold has a purity of 58.3%. How many moles of gold are in 155 grams of 14 carat gold?...

## Question:

{eq}14 {/eq} carat gold has a purity of {eq}58.3 \% {/eq}. How many moles of gold are in {eq}155 {/eq} grams of {eq}14 {/eq} carat gold? Give your answer in units of moles.

## Molecular Mass:

The total mass of 1-mole molecules of a substance is the molar mass of the substance. It is the sum of the masses of individual atoms that form the compound.

For example, the molar mass of water is 18 g/mol. This means the mass of 1 mole of water molecules is 18 g.

Given:

• {eq}14 {/eq} carat gold has a purity of {eq}58.3 \% {/eq}.
• Amount of {eq}14 {/eq} carat gold is{eq}155 {/eq} grams.

An effective amount of gold present in that 155 g is

{eq}\begin{align*} m & = 58.3 \% \times 155 \ g \\ & = 90.365 \ g \end{align*} {/eq}

We know the molar mass of {eq}gold {/eq} is M = 197 g/mol.

Number of moles of {eq}gold {/eq} present in m = 90.365 g of the gas is given by

{eq}\begin{align*} n & = \frac{m}{M} \\ & = \frac{90.365 \ g}{197 \ g/mol} \\ & = 0.4587 \ moles \Rightarrow(Answer) \end{align*} {/eq} 