Question

now it’s your turn... • materials / everyday products • table salt (nacl) if a bag of chips contains 1.50 g of nacl (salt), • how many formula units of nacl is this? • how many sodium atoms does this represent?

Explanation:

Part 1: Formula Units of NaCl

Step1: Calculate moles of NaCl

Molar mass of NaCl: $M(\text{NaCl}) = 22.99 + 35.45 = 58.44\ \text{g/mol}$
Moles, $n = \frac{\text{mass}}{\text{molar mass}} = \frac{1.50\ \text{g}}{58.44\ \text{g/mol}} \approx 0.02567\ \text{mol}$

Step2: Calculate formula units (using Avogadro's number)

Formula units = $n \times N_A$, where $N_A = 6.022 \times 10^{23}\ \text{mol}^{-1}$
Formula units = $0.02567\ \text{mol} \times 6.022 \times 10^{23}\ \text{mol}^{-1} \approx 1.546 \times 10^{22}$

Part 2: Sodium Atoms

Step1: Relate NaCl to Na atoms

In 1 formula unit of NaCl, there is 1 Na atom. So moles of Na = moles of NaCl = $0.02567\ \text{mol}$

Step2: Calculate Na atoms

Atoms of Na = $n \times N_A = 0.02567\ \text{mol} \times 6.022 \times 10^{23}\ \text{mol}^{-1} \approx 1.546 \times 10^{22}$

Answer:

s:

• Formula units of NaCl: $\boldsymbol{\approx 1.55 \times 10^{22}}$ (or $1.54 \times 10^{22}$ depending on precision)
• Sodium atoms: $\boldsymbol{\approx 1.55 \times 10^{22}}$ (or $1.54 \times 10^{22}$)