14-carat gold has a purity of 58.3%. How many moles of gold are in 124 grams of 14-carat gold?...

Question:

14-carat gold has a purity of 58.3%. How many moles of gold are in 124 grams of 14-carat gold? Answer in units of moles.

Moles:

A mole is the quantity of anything that has the same number of particles found in 12 grams of carbon-12. A mole of carbon-12 contains {eq}6.022\times 10^{23}{/eq} carbon atoms. This number is constant for one mole of any element and is known as Avogadro's constant.

Answer and Explanation:

Because 14-carat gold has a purity of 58.3%, it means that for every 100 grams of gold, only 58.3 grams of pure gold is available. Therefore, the gold present in 124 grams of 14-carat gold is:

58.3% of 124 grams = {eq}\frac {58.2}{100} \times 124 = 72.168 grams{/eq}

{eq}Number\; of\; Moles\; =\; \frac {Given\; Mass}{Molar\; Mass}{/eq}

The mass of one mole of a substance in grams is called its molar mass.

  • Given mass = 72.168 grams
  • Molar mass of gold = 196.97 g/mol

Therefore:

{eq}Number\; of\; Moles\; of\; Gold\; =\; \frac {72.168 g}{196.97 g/mol} = 0.367\; moles {/eq}

0.367 moles of gold are present in 124 grams of 14-carat gold.


Learn more about this topic:

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How to Convert Grams to Moles

from Analytical Chemistry: Help & Review

Chapter 4 / Lesson 8
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