Question

1. how many atoms are in 50.0 g of sodium (na)? 6. how many atoms are in 125 g of calcium (ca)? 7. how many atoms are in 10.5 g of helium (he)? 8. how many atoms are in 75.0 g of carbon (c)?

Explanation:

Question 5:

Step1: Find moles of Na

Molar mass of Na is 22.99 g/mol. Moles = mass / molar mass.
$n = \frac{50.0\ \text{g}}{22.99\ \text{g/mol}} \approx 2.175\ \text{mol}$

Step2: Find atoms using Avogadro's number

Avogadro's number $N_A = 6.022 \times 10^{23}\ \text{atoms/mol}$. Atoms = moles × $N_A$.
$N = 2.175\ \text{mol} \times 6.022 \times 10^{23}\ \text{atoms/mol} \approx 1.310 \times 10^{24}\ \text{atoms}$

Step1: Find moles of Ca

Molar mass of Ca is 40.08 g/mol. Moles = mass / molar mass.
$n = \frac{125\ \text{g}}{40.08\ \text{g/mol}} \approx 3.119\ \text{mol}$

Step2: Find atoms using Avogadro's number

Atoms = moles × $N_A$.
$N = 3.119\ \text{mol} \times 6.022 \times 10^{23}\ \text{atoms/mol} \approx 1.878 \times 10^{24}\ \text{atoms}$

Step1: Find moles of He

Molar mass of He is 4.003 g/mol. Moles = mass / molar mass.
$n = \frac{10.5\ \text{g}}{4.003\ \text{g/mol}} \approx 2.623\ \text{mol}$

Step2: Find atoms using Avogadro's number

Atoms = moles × $N_A$.
$N = 2.623\ \text{mol} \times 6.022 \times 10^{23}\ \text{atoms/mol} \approx 1.579 \times 10^{24}\ \text{atoms}$

Answer:

$\approx 1.31 \times 10^{24}$ atoms

Question 6: