Solutions Part II Units of Concentration loosely from

Solutions Part II: Units of Concentration (loosely from Jespersen Chap. 13 Sec 5) Dr. C. Yau Fall 2014 1

Units of Concentration Molarity (M) Molality (m) Mole fraction & mole % Mass %, ppt, ppm, ppb 2

Percent by Mass 1 million = 1, 000 = 106 1 billion = 1, 000, 000 = 109 3

What does 15% w/w mean? w/w means 15% w/w means 1 ppt means. . ? 15 ppb means. . ? 4

Example 13. 2 p. 598 Please don’t waste time copying the question. You can get it later from your textbook. Seawater is typically 3. 5% sea salt and has a density of about 1. 03 g m. L-1. How many grams of sea salt would be needed to prepare enough seawater solution to completely fill a 62. 5 L aquarium? 5

Molality vs Molarity Know WHEN m is almost the same as M. . . under what conditions? Ans. m = M for very dilute solutions If we have a very dilute solution, such as 0. 0005 M which is In such a solution, there is very little solute present, therefore 1 L soln = 1 L water. 6

Ex 13. 3 p. 599 An experiment calls for a 0. 150 m solution of sodium chloride in water. How many grams of Na. Cl would have to be dissolved in 500. 0 g of water to prepare a solution of this molality? 7

Interconversion of Units of Concentration Example 13. 4 p. 601 What is the molality of 10. 0% w/w aq Na. Cl? 8

Example 13. 5 p. 602 A certain supply of conc hydrochloric acid has a concentration of 36. 0% HCl. The density of the solution is 1. 19 g m. L-1. Calculate the molar concentration of HCl. 9

p. 629 #13. 48 What is the molality of Na. Cl in a solution that is 3. 000 M Na. Cl, with a density of 1. 07 g m. L-1? Be sure to learn how to convert between different units of concentration. Practice Exer 6 -8 on p. 600 Exer 9 & 10 on p. 602 Exer 11 & 12 on p. 603 Do as many as possible: p. 629 #48 -57. 10