Question

calculate the mass, in grams, of 3.37e21 atoms of arsenic. the mass of one mole of arsenic is 74.92 g.

Explanation:

Step1: Find moles of arsenic

Use Avogadro's number ($6.022\times10^{23}$ atoms/mol). Moles = $\frac{\text{number of atoms}}{\text{Avogadro's number}}$ = $\frac{3.37\times10^{21}}{6.022\times10^{23}}$

Step2: Calculate mass

Mass = moles × molar mass. Molar mass = 74.92 g/mol. So mass = ($\frac{3.37\times10^{21}}{6.022\times10^{23}}$) × 74.92
First, $\frac{3.37\times10^{21}}{6.022\times10^{23}}$ ≈ 0.005596 mol. Then, 0.005596 × 74.92 ≈ 0.420 g.

Answer:

0.420 g