Types of Concentration Expressions

Transcription

1 Chapter 12 Lecture Chapter 12 Solutions 12.4 Concentrations of Solutions Learning Goal Calculate the concentration of a solute in a solution; use concentration as a conversion factor to calculate the amount of solute or solution. Fifth Edition Percent Concentration 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 2 Types of Concentration Expressions Mass Percent 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 4 Calculating Mass Percent Mass of Solution 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 5 6 1

2 Calculating Solution Concentration 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 Volume Percent 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 A volume percent (v/v) solution is prepared by using a specific volume (ml) of solute (liquid) adding water to the volume line 9 10 Mass/Volume Percent (v/v) Concentration Mass/volume percent (m/v) describes the mass of solute in grams per 100 ml of solution. the solute in units of grams and solution volume in milliliters. Mass/Volume Percent (v/v) Concentration Mass/volume percent is widely used in hospitals and pharmacies for preparation of medicines and intravenous solutions. A 5% (m/v) solution of glucose contains 5 g of glucose in exactly 100 ml solution. has a combined volume of glucose and water to make 100 ml solution. 2

3 Molarity (M) Molarity (M) is a concentration term for solutions the moles of solute in 1 L of solution moles of solute liter of solution Preparing a 6.0 M Solution A 6.00 M NaOH solution is prepared by weighing out 60.0 g of NaOH (1.50 mol) and adding water to make L of a 6.00 MNaOH solution Calculating Molarity Example of Calculating Molarity What is the molarity of L of a NaOH solution if it contains 6.00 g of NaOH? STEP 1 State the given and needed quantities. Given 6.00 g of NaOH in L of solution Need molarity (M) STEP 2 Write a plan to calculate molarity. molarity (M) = moles of solute liters of solution grams of NaOH moles of NaOH molarity Example of Calculating of Molarity (continued) STEP 3 Write equalities and conversion factors needed. 1 mol of NaOH = g of NaOH 1 mol NaOH and g NaOH g NaOH 1 mol NaOH STEP 4 Set up problem to calculate molarity g NaOH x 1 mol NaOH = mol of NaOH g NaOH mol NaOH = mol L solution 1 L = M NaOH solution What is the molarity of 325 ml of a solution containing 46.8 g of NaHCO 3? A M NaHCO 3 solution B M NaHCO 3 solution C M NaHCO 3 solution

4 Conversion Factors and Concentration Expressions Write two conversion factors for each solution. A. 8.50% (m/m) NaOH B. 5.75% (v/v) ethanol 20 Using Concentration to Calculate Mass or Volume Example of Using Percent Factors 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 (continued) 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 How many grams of NaOH are needed to prepare 75.0 g of a 14.0% (m/m) NaOH solution? A g of NaOH B g of NaOH C. 536 g of NaOH 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

5 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 Example of Using Molarity in Calculations How many grams of KCl are needed to prepare L of a M KCl solution? STEP 1 State the given and needed quantities. Given L of a M KCl solution Need grams of KCl STEP 2 Write a plan to calculate mass or volume. liters of KCl solution grams of KCl moles of KCl Example of Using Molarity in Calculations (continued) STEP 3 Write equalities and conversion factors needed. 1 mol of KCl = g of KCl 1 mol KCl and g KCl g KCl 1 mol KCl 1 L of KCl solution = mol of KCl 1 L KCl solution and mol KCl mol KCl 1 L KCl solution Example of Using Molarity in Calculations (continued) STEP 4 Set up problem to calculate mass or volume L x mol KCl x g KCl = 6.71 g of KCl 1 L 1 mol KCl How many grams of AlCl 3 are needed to prepare 37.8 ml of a M AlCl 3 solution? A g of AlCl 3 B g of AlCl 3 C g of AlCl 3 How many milliliters of a 2.00 M HNO 3 solution contain 24.0 g of HNO 3? A ml of HNO 3 solution B ml of HNO 3 solution C ml of HNO 3 solution

6 Chapter 12 Lecture Chapter 12 Solutions 12.5 Dilution of Solutions Fifth Edition Dilution In a dilution, water is added volume increases concentration decreases Learning Goal Describe the dilution of a solution; calculate the unknown concentration or volume when a solution is diluted. 32 Comparing Initial and Diluted Solutions Calculating Dilution Quantities In the initial and diluted solution, the moles of solute are the same the concentrations and volumes are related by the equation M 1 V 1 = M 2 V 2 initial diluted Dilution of a Solution Dilution of a Solution A doctor orders ml of a 35.0% (m/v) dextrose solution. If you have a 50.0% (m/v) dextrose solution, how many milliliters would you use to prepare ml of 35.0% (m/v) dextrose solution? STEP 1 Prepare a table of the concentrations and volumes of the solutions. A doctor orders ml of a 35.0% (m/v) dextrose solution. If you have a 50.0% (m/v) dextrose solution, how many milliliters would you use to prepare ml of 35.0% (m/v) dextrose solution? STEP 2 Rearrange the dilution expression to solve for the unknown quantity. 6

7 Dilution of a Solution Molarity of a Diluted Solution A doctor orders ml of a 35.0% (m/v) dextrose solution. If you have a 50.0% (m/v) dextrose solution, how many milliliters would you use to prepare ml of 35.0% (m/v) dextrose solution? STEP 3 Substitute the known quantities into the dilution expression and calculate. What is the molarity of a solution when 75.0 ml of a 4.00 M KCl solution is diluted to a volume of 500. ml? STEP 1 Prepare a table of the concentrations and volumes of the solutions. Molarity of a Diluted Solution Molarity of a Diluted Solution What is the molarity of a solution when 75.0 ml of a 4.00 M KCl solution is diluted to a volume of 500. ml? STEP 2 Rearrange the dilution expression to solve for the unknown quantity. What is the molarity of a solution when 75.0 ml of a 4.00 M KCl solution is diluted to a volume of 500. ml? STEP 3 Substitute the known quantities into the dilution expression and calculate. What is the final volume, in milliliters, if 15.0 ml of a 1.80 M KOH solution is diluted to give a M KOH solution? A ml of M KOH solution B ml of M KOH solution C ml of M KOH solution 41 7