The molar mass of NaCl is 58.44 g/mol, which means that one mole of NaCl contains 6.022 x 10^23 formula units (Avogadro's number).
To determine the number of formula units in a teaspoon of salt, we need to first determine how many moles of NaCl are present in 5.0 g of salt. This can be done using the following formula:
moles = mass / molar mass
moles = 5.0 g / 58.44 g/mol = 0.0854 mol
Next, we can use Avogadro's number to convert moles of NaCl to formula units:
formula units = moles x Avogadro's number
formula units = 0.0854 mol x 6.022 x 10^23 formula units/mol = 5.14 x 10^22 formula units
Therefore, there are approximately 5.14 x 10^22 formula units of NaCl in a teaspoon of salt.