Question

5.85 g of NaCl are dissolved in 500 cm³ of water. Calculate the formality of the solution.

Answer 1

Given: Mass of NaCl = 5.85 g

Volume of solution = 500 cm³ = 0.5 L

Formula mass of NaCl = 58.5 g/mol

Moles (formula units) = `5.85/58.5` = 0.1

Formality is similar to molarity but used when solutes do not exist as individual molecules in solution (as in ionic compounds like NaCl).

Formality (F) = `"Moles of solute"/"Volume in litres"`

= `0.1/0.5`

= 0.2 F

∴ Formality of the solution is 0.2 F.