Basic Chemistry Copyright © 2011 Pearson Education, Inc. 1 Chapter 12 Solutions 12.4 Percent Concentration

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 2 The concentration of a solution is the amount of solute dissolved in a specific amount of solution amount of solute amount of solution as percent concentration describes the amount of solute that is dissolved in 100 parts of solution amount of solute 100 parts solution Percent Concentration

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 3 The mass percent (m/m) concentration is the percent by mass of solute in a solution Mass percent (m/m) = mass of solute x 100% mass of solute + mass of solvent is the g of solute in exactly100 g of solution Mass percent = g of solute x 100% 100. g of solution Mass Percent

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 4 Mass percent (%m/m) is calculated from the grams of solute (g KCl) and the grams of solution (g KCl solution). g of KCl = 8.00 g g of solvent (water) = g g of KCl solution = g 8.00 g KCl (solute) x 100 = 16.0% (m/m) g KCl solution Calculating Mass Percent

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 5 Mass of Solution

Basic Chemistry Copyright © 2011 Pearson Education, Inc. Calculating Solution Concentration 6

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 7 A solution is prepared by mixing 15.0 g of Na 2 CO 3 and 235 g of H 2 O. Calculate the mass percent (m/m) of the solution. A. 15.0% (m/m) Na 2 CO 3 B. 6.38% (m/m) Na 2 CO 3 C. 6.00% (m/m) Na 2 CO 3 Learning Check

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 8 STEP 1 Determine quantities of solute and solution. Mass of solute = 15.0 g of Na 2 CO 3 Mass of water= 235 g of water Mass of solution= 250. g of Na 2 CO 3 solution STEP 2 Write the % concentration expression. Mass percent (m/m) = grams of Na 2 CO 3 x 100% grams of Na 2 CO 3 solution Solution

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 9 STEP 3 Substitute solute and solution quantities into the expression Mass percent (m/m) = 15.0 g Na 2 CO 3 x 100% 250. g Na 2 CO 3 solution = 6.00% (m/m) Na 2 CO 3 solution (C) Solution (continued)

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 10 The volume percent (v/v) is percent volume (mL) of solute (liquid) to volume (mL) of solution Volume percent(v/v) = mL of solute x 100% mL of solution solute (mL) in 100 mL of solution Volume percent (v/v) = mL of solute x 100% 100 mL of solution Volume Percent

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 11 A volume percent (v/v) solution is prepared by using a specific volume (mL) of solute (liquid) adding water to the volume line Volume Percent

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 12 Percent Conversion Factors Two conversion factors can be written for each type of percent value.

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 13 Write two conversion factors for each solution. A. 8.50% (m/m) NaOH B. 5.75% (v/v) ethanol Learning Check

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 14 A. 8.50% (m/m) NaOH solution 100 g of NaOH solution = 8.50 g of NaOH 8.50 g NaOH and 100 g NaOH solution 100 g NaOH solution 8.50 g NaOH B. 5.75% (v/v) ethanol solution 100 mL of ethanol solution = 5.75 mL of ethanol 5.75 mL ethanol and 100 mL solution 100 mL solution 5.75 mL ethanol Solution

Basic Chemistry Copyright © 2011 Pearson Education, Inc. Using Concentration to Calculate Mass or Volume 15

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 16 How many grams of NaCl are needed to prepare 225 g of a 10.0% (m/m) NaCl solution? STEP 1 State the given and needed quantities. Given 225 g of NaCl solution; 10.0% (m/m) NaCl solution Need grams of NaCl STEP 2 Write a plan to calculate mass or volume. grams of NaCl solution grams of NaCl Example of Using Percent Factors

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 17 STEP 3 Write equalities and conversion factors. 100 g of NaCl solution = 10.0 g of NaCl 10.0 g NaCl and 100 g NaCl solution 100 g NaCl solution 10.0 g NaCl STEP 4 Set up problem to calculate mass or volume. 225 g NaCl solution x 10.0 g NaCl = 22.5 g of NaCl 100 g NaCl solution Example of Using Percent Factors (continued)

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 18 How many grams of NaOH are needed to prepare 75.0 g of a 14.0% (m/m) NaOH solution? A.10.5 g of NaOH B g of NaOH C.536 g of NaOH Learning Check

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 19 STEP 1 State the given and needed quantities. Given 75.0 g of NaOH of a 14.0% (m/m) solution Need grams of NaOH STEP 2 Write a plan to calculate mass or volume. grams of NaOH solution grams of NaOH Solution

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 20 STEP 3 Write equalities and conversion factors. 100 g of NaOH solution = 14.0 g of NaOH 14.0 g NaOH and 100 g solution 100 g solution 14.0 g NaOH STEP 4 Set up problem to calculate mass or volume g solution x 14.0 g NaOH = 10.5 g of NaOH (A) 100 g solution 14.0 % (m/m) factor Solution (continued)

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 21 How many milliliters of a 5.75% (v/v) ethanol solution can be prepared from 2.25 mL of ethanol? A mL B mL C mL Learning Check

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 22 STEP 1 State the given and needed quantities. Given 2.25 ml of ethanol 5.75% (v/v) ethanol solution Need milliliters of ethanol solution STEP 2 Write a plan to calculate mass or volume. mL of ethanol mL of ethanol solution Solution

Basic Chemistry Copyright © 2011 Pearson Education, Inc. 23 STEP 3 Write equalities and conversion factors. 100 mL of ethanol solution = 5.75 mL of ethanol 5.75 mL ethanol and 100 mL solution 100 mL solution 14.0 mL ethanol STEP 4 Set up problem to calculate mass or volume. 5.75% (v/v) inverted 2.25 mL ethanol x 100 mL ethanol solution 5.75 mL ethanol = 39.1 mL of solution (C) Solution (continued)