1. Physical Properties of Solutions Chapter 13

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4. Concentration Units Mass percentage ppm and ppb Mole fraction Molarity Molality Concentration - amount of solute present in a given quantity of solvent or solution:

5. Concentration Units Mass percentage (w/w) % by mass = x 100% mass of solute mass of solute + mass of solvent = x 100% (w/w) mass of solute mass of solution Mole Fraction (X) X A = moles of A sum of moles of all components

6. Parts per million (ppm) Parts per billion (ppb) Concentration Units

7. M = moles of solute liters of solution Molarity (M) Molality (m) m = moles of solute mass of solvent (kg)

8. What is the molality of a solution made by dissolving 36.5 g of naphthalene (C 10 H 8 ) in 425 g of toluene (C 7 H 8 )? Answer: 0.671 m Practice Exercise p 544

9. What is the molality of a 5.86 M ethanol (C 2 H 5 OH) solution whose density is 0.927 g/mL? m =m = moles of solute mass of solvent (kg) M = moles of solute liters of solution 5.86 moles ethanol = 270 g ethanol Assume 1 L of solution: (0.927 g/mL) (1000 mL) = 927 g of solution mass of solvent = mass of solution – mass of solute = 927 g – 270 g = 657 g = 0.657 kg m =m = moles of solute mass of solvent (kg) = 5.86 moles C 2 H 5 OH 0.657 kg solvent = 8.92 m

10. (a)Calculate the mass percentage of NaCl in a solution containing 1.50 g of NaCl in 50.0 g of water. (b) A commercial bleaching solution contains 3.62 %(w/w) sodium hypochlorite, NaOCl. What is the mass of NaOCl in a bottle containing 2.50 kg of bleaching solution? Answer: (a) 2.91% (b) 90.5 g of NaOCl Practice Exercise p 543

11. An aqueous solution of hydrochloric acid contains 36% HCl by mass. Calculate the mole fraction of HCl in the solution. Sample Exercise 13.6 Calculation of Mole Fraction Assume we have 100. g of solution:

12. Conversion of Concentration Units If we know the density of the solution, we can calculate the molality from the molarity and vice versa. Fig 13.19 Calculating molality and molarity