Question

part a
how many gold atoms does it contain?
express your answer to three significant figures.
n = au atoms
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1. the mole concept - converting between grams and number of atoms read

section 6.3. you can click on the review link to access the section in your etext.
a pure gold ring contains 0.0104 mmol (millimol) au

Explanation:

Step1: Convert millimol to mol

We know that \(1\space mmol = 1\times10^{- 3}\space mol\). So, \(n = 0.0104\space mmol=0.0104\times10^{-3}\space mol\)

Step2: Use Avogadro's number

Avogadro's number \(N_A = 6.022\times 10^{23}\space atoms/mol\). The number of atoms \(N=n\times N_A\)

Substitute \(n = 0.0104\times 10^{-3}\space mol\) and \(N_A=6.022\times 10^{23}\space atoms/mol\) into the formula:

\(N=(0.0104\times 10^{- 3}\space mol)\times(6.022\times 10^{23}\space atoms/mol)\)

\(N = 0.0104\times6.022\times10^{20}\)

\(N=6.26288\times10^{18}\)

Rounding to three significant figures: \(N = 6.26\times 10^{18}\)

Answer:

\(6.26\times 10^{18}\)