Question

part 2 of 3
find the mass of $2.11 \times 10^{23}$ molecules $\ce{h2s}$.
answer in units of g. answer in units of g.

1. 12.7599
2. 14.002
3. 16.2604
4. 11.913
5. 18.0671
6. 15.8652
7. 14.4537
8. 18.3494
9. 16.825
10. 15.5264

Explanation:

Step1: Find moles from molecules

Use Avogadro's number ($N_A = 6.022\times10^{23}$ molecules/mol). Moles ($n$) = $\frac{\text{number of molecules}}{N_A}$.
$n = \frac{2.11\times10^{23}}{6.022\times10^{23}} \approx 0.3504$ mol.

Step2: Calculate molar mass of $\text{H}_2\text{S}$

Molar mass of H = 1.008 g/mol, S = 32.06 g/mol.
Molar mass ($M$) = $2\times1.008 + 32.06 = 34.076$ g/mol.

Step3: Find mass using $m = n\times M$

$m = 0.3504\ \text{mol} \times 34.076\ \text{g/mol} \approx 11.94$ g (closest to 11.913).

Answer:

1. 11.913