Answer:
5.80 M
Explanation:
In this problem, the solute is NaCl and the solvent is water. To find the molality, you need to (1) convert grams NaCl to moles NaCl (via molar mass), then (2) convert grams H₂O to kilograms H₂O, and then (3) calculate the molality (via molality equation). The final answer should have 3 sig figs to match the sig figs of the given values.
(Step 1)
Molar Mass (NaCl): 22.990 g/mol + 35.453 g/mol
Molar Mass (NaCl): 58.443 g/mol
14.3 grams NaCl 1 mole
-------------------------- x ------------------------ = 0.245 moles NaCl
58.443 grams
(Step 2)
1,000 g = 1 kg
42.2 grams H₂O 1 kg
-------------------------- x ----------------------- = 0.0422 kg H₂O
1,000 grams
(Step 3)
Molality = moles solute / mass solvent (kg)
Molality = 0.245 moles NaCl / 0.0422 kg H₂O
Molality = 5.80 M
