Question

4.07×10²¹ ca atoms
express your answer using three significant figures.
ν =
mol

Explanation:

Step1: Recall Avogadro's number

Avogadro's number is \( N_A = 6.022\times 10^{23}\) atoms/mol. To find the number of moles (\(n\)), we use the formula \( n=\frac{N}{N_A}\), where \(N\) is the number of atoms.

Step2: Substitute the values

Given \( N = 4.07\times 10^{21}\) atoms and \( N_A=6.022\times 10^{23}\) atoms/mol.

$$ n=\frac{4.07\times 10^{21}}{6.022\times 10^{23}} $$

First, divide the coefficients: \( \frac{4.07}{6.022}\approx0.676\)
Then, divide the powers of 10: \( \frac{10^{21}}{10^{23}} = 10^{-2}\)
Multiply these results: \( 0.676\times 10^{-2}=6.76\times 10^{-3}\) (after adjusting to three significant figures)

Answer:

\( 6.76\times 10^{-3}\) mol