A salt crystal has a mass of 0.27 mg. How many NaCl formula units does it contain?

Verified step by step guidance

1. Convert the mass of the salt crystal from milligrams to grams. Since 1 mg = 0.001 g, multiply 0.27 mg by 0.001 to get the mass in grams.
2. Calculate the number of moles of NaCl using the formula: \( \text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \). The molar mass of NaCl is approximately 58.44 g/mol.
3. Use Avogadro's number to find the number of formula units. Avogadro's number is \( 6.022 \times 10^{23} \) formula units/mol.
4. Multiply the number of moles of NaCl by Avogadro's number to find the total number of NaCl formula units in the crystal.
5. Ensure all units are consistent and check calculations for accuracy.

Key Concepts

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For sodium chloride (NaCl), the molar mass is approximately 58.44 g/mol, calculated by adding the atomic masses of sodium (Na) and chlorine (Cl). Understanding molar mass is essential for converting between mass and the number of formula units in a sample.

Avogadro's Number

Avogadro's number, approximately 6.022 x 10²³, is the number of particles (atoms, molecules, or formula units) in one mole of a substance. This constant allows chemists to relate the macroscopic scale of substances to the microscopic scale, enabling calculations of how many formula units are present in a given mass of a compound.

Unit Conversion

Unit conversion is the process of converting a quantity expressed in one set of units to another set of units. In this context, it involves converting the mass of the salt crystal from milligrams to grams to facilitate the calculation of the number of NaCl formula units using the molar mass and Avogadro's number. Mastery of unit conversion is crucial for accurate chemical calculations.