Question

3.9×10²⁴ pb atoms
express your answer using two 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 (\(
u \)), we use the formula \(
u=\frac{N}{N_A}\), where \( N = 3.9\times 10^{24}\) Pb atoms.

Step2: Substitute values into the formula

Substitute \( N = 3.9\times 10^{24}\) and \( N_A=6.022\times 10^{23}\) into the formula:

$$ u=\frac{3.9\times 10^{24}}{6.022\times 10^{23}} $$

First, simplify the exponents: \( \frac{10^{24}}{10^{23}} = 10\). Then, calculate \( \frac{3.9\times 10}{6.022}=\frac{39}{6.022}\approx 6.476\).

Step3: Round to two significant figures

The value \( 6.476\) rounded to two significant figures is \( 6.5\).

Answer:

\( 6.5\)