18. how many moles are in 5.49·10²⁵ atoms gold? mol au

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Accepted Answer

# Explanation:
## Step1: Recall Avogadro's number
Avogadro's number $N_A = 6.022\times10^{23}\text{ atoms/mol}$. The formula to find the number of moles $n$ is $n=\frac{N}{N_A}$, where $N$ is the number of atoms.
## Step2: Substitute the values
Given $N = 5.49\times 10^{25}\text{ atoms}$. Then $n=\frac{5.49\times 10^{25}\text{ atoms}}{6.022\times10^{23}\text{ atoms/mol}}$.
$$
\begin{align*}
n&=\frac{5.49}{6.022}\times\frac{10^{25}}{10^{23}}\text{ mol}\
&=\frac{5.49}{6.022}\times10^{25 - 23}\text{ mol}\
&=\frac{5.49}{6.022}\times10^{2}\text{ mol}\
&\approx0.912\times10^{2}\text{ mol}\
& = 91.2\text{ mol}
\end{align*}
$$

# Answer:
$91.2$

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Question

Explanation:

Step1: Recall Avogadro's number

Step2: Substitute the values

Answer: