Question

Calculate the molality of a solution prepared by dissolving 25.0 g of sodium chloride (NaCl) in 625 g of water

Answer 1

Answer: m= 0.69 m or mol/kg

Explanation: Molality is expressed as moles per unit kilograms of solvent or m= n / kg

First convert 25.0 g NaCl to moles

25.0 g NaCl x 1 mole NaCl / 58 g NaCl

= 0.43 moles NaCl

Next convert 625 g H2O to kilograms

625 g H2O x 1 kg / 1000 g H2O

= 0.625 kg H2O

Substitute the values in the formula

m = n / kg

   = 0.43 mole NaCl / 0.625 kg

   = 0.69 m or mole / kg