Which of the following steps is necessary to convert the mass of a sample of NaCl to the number of NaCl formula units present?

• A. Divide the mass by the molar mass of NaCl, then multiply by Avogadro's number.
• B. Multiply the mass by the molar mass of NaCl, then divide by Avogadro's number.
• C. Divide the mass by Avogadro's number, then multiply by the molar mass of NaCl.
• D. Multiply the mass by Avogadro's number, then divide by the molar mass of NaCl.

Answer: (A)

Verified step by step guidance

1. Understand that the goal is to find the number of formula units of NaCl from a given mass. This requires converting mass to moles first, then moles to formula units.
2. Recall that the molar mass of NaCl (in grams per mole) allows you to convert from mass to moles using the formula: \(\text{moles} = \frac{\text{mass}}{\text{molar mass}}\).
3. Once you have the number of moles, use Avogadro's number (\$6.022 \times 10^{23}\( formula units per mole) to convert moles to formula units: \)\text{formula units} = \text{moles} \times 6.022 \times 10^{23}$.
4. Combine these two steps into one expression: \(\text{formula units} = \frac{\text{mass}}{\text{molar mass}} \times 6.022 \times 10^{23}\).
5. Therefore, the necessary step is to divide the mass by the molar mass of NaCl, then multiply by Avogadro's number to find the number of formula units.