Concentration. The concentration of a solution is the amount of solute dissolved in a specific amount of solution.

Transcription

1 Concentration The concentration of a solution is the amount of solute dissolved in a specific amount of solution. can be represented as mass percent, volume percent, mass/volume percent, or molarity.

2 Mass Percent Concentration Mass percent (m/m) concentration is the grams of the solute in exactly 100 g of solution (mass solute + mass solvent).

3 Calculating Mass Percent Suppose we prepared a solution by mixing 8.00 g of KCl (solute) with g of water (solvent).

4 Mass of Solution When water is added to 8.00 g of KCl to form g of KCl solution, the mass percent concentration is 16.0% (m/m).

5 Guide to Calculating Solution Concentration

6 Learning Check A solution is prepared with 15.0 g of Na 2 CO 3 and 235 g of H 2 O. What is the mass percent (m/m) of Na 2 CO 3 in the solution?

7 Solution A solution is prepared with 15.0 g of Na 2 CO 3 and 235 g of H 2 O. What is the mass percent (m/m) of Na 2 CO 3 in the solution? Determine the quantities of solute and solution. Analyze the Problem. Quantity of Solute Quantity of Solution 15.0 g Na 2 CO g Na 2 CO g H 2 O = 250 g Na 2 CO 3 solution Concentration? g Na 2 CO 3 /100 g Na 2 CO 3 solution Type of Solution Problem mass percent (m/m)

8 Solution A solution is prepared with 15.0 g of Na 2 CO 3 and 235 g of H 2 O. What is the mass percent (m/m) of Na 2 CO 3 in the solution? Write the concentration expression. Substitute solute and solution quantities into the expression and calculate.

9 Volume Percent The volume percent (v/v) is percent by volume of solute (liquid) in a solution, and A 7% (v/v) solution contains 7 ml of solute per 100 mlof solution.

10 Learning Check A bottle contains 59 ml of lemon extract solution. If the solution contains 49 ml of alcohol, what is the volume percent (v/v) of the alcohol in the extract solution?

11 Solution A bottle contains 59 ml of lemon extract solution. If the solution contains 49 ml of alcohol, what is the volume percent (v/v) of the alcohol in the extract solution? Step 1 Determine the quantities of solute and solution. Quantity of Solute Quantity of Solution 49 ml alcohol Analyze the Problem. Concentration 59 ml extract solution? ml alcohol/100 ml solution Type of Solution Problem volume percent (v/v)

12 Solution A bottle contains 59 ml of lemon extract and 49 ml of alcohol, what is the volume percent (v/v) of the alcohol in the extract solution? Write the concentration expression. Substitute solute and solution quantities into the expression and calculate.

13 Mass/Volume Percent The mass/volume percent (m/v) is widely used for preparation of intravenous solutions and medications. A 5% mass/volume percent solution contains 5 grams of solute per 100 ml of solution.

14 Preparation of a Solution: Mass/Volume Percent Water is added to 5.0 g of KI to make 250 ml of KI solution. The mass/volume percent of the solution is 2.0% (m/v) KI solution.

15 Molarity, (Moles/L) Concentrations are frequently measured using molarity (M), a concentration that states the number of moles of solute in exactly 1 liter of solution. If 2.0 moles of NaCl are dissolved in enough water to prepare 1.0 L of solution, the resulting NaCl solution has a molarity of 2.0 M.

16 Molarity, (moles/l) A solution of 2.0 moles of NaCl and water added to the 1-L mark is a 2.0 M NaCl solution.

17 Learning Check What is the molarity of a L solution that contains 46 g of KCl?

18 Solution What is the molarity of a L solution that contains46 g of KCl? Step 1 Determine the quantities of solute and solution. Analyze the Problem. Quantity of Solute Quantity of Solution Concentration 46 g of KCl L KCl solution? M of KCl solution or (? moles KCl/1 L solution) Type of Solution Problem Molarity (M)

19 Solution What is the molarity of a L solution that contains 46 g of KCl? Step 1 Determine the quantities of solute and solution. 1 mole of KCl = 74.6 g of KCl

20 Solution What is the molarity of a L solution that contains 46 g of KCl? Step 2 Write the concentration expression. Step 3 Substitute solute and solution quantities into the expression and calculate.

21 Summary of Concentration Expressions 2013 Pearson Education, Inc. Chapter 8, Section 1 21

22 Using Concentrations as Conversion Factors The value of 100 in the denominator of a percent expression is an exact number. Examples of conversion factors from oncentrations are: 2013 Pearson Education, Inc. Chapter 8, Section 1 22

23 Learning Check Write two conversion factors for each solution % (m/m) NaOH % (m/v) HCl M NaOH

24 Solution % (m/m) NaOH % (m/v) HCl M NaOH

25 Guide to Using Concentration to Calculate Mass or Volume

26 Learning Check How many grams of NaCl are needed to prepare 225 g of a 10.0% (m/m) NaCl solution?

27 Solution 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. Analyze the Problem. Given 225 g NaCl solution 10.0% (m/m) NaCl solution Need? grams NaCl

28 Solution How many grams of NaCl are needed to prepare 225 g of a 10.0% (m/m) NaCl solution? Step 2 Write a plan to calculate the mass or volume. g of solution % (m/m) factor g of NaCl

29 Solution How many grams of NaCl are needed to prepare 225 g of a 10.0% (m/m) NaCl solution? Step 3 Write equalities and conversion factors g of NaCl = 100 g of NaCl solution Step 4 Set up the problem to calculate the mass or volume.

30 Learning Check How many liters of a 2.00 M NaCl solution are needed to provide 67.3 g of NaCl?

31 Solution How many liters of a 2.00 M NaCl solution are needed to provide 67.3 g of NaCl? Step 1 State the given and needed quantities. Analyze the Problem. Given 67.3 g NaCl 2.00 M NaCl solution Need? liters NaCl solution

32 Solution How many liters of a 2.00 M NaCl solution are needed to provide 67.3 g of NaCl? Step 2 Write a plan to calculate the mass or volume. g of NaCl molar moles molarity L of NaCl solution mass NaCl

33 Solution How many liters of a 2.00 M NaCl solution are needed to provide 67.3 g of NaCl? Step 3 Write equalities and conversion factors. 1 mole of NaCl = 58.5 g of NaCl 2.00 mole of NaCl = 1 L of NaCl solution

34 Solution How many liters of a 2.00 M NaCl solution are needed to provide 67.3 g of NaCl? Step 4 Set up the problem to calculate the mass or volume.

35 Dilution In a process called dilution, a solvent, usually water, is added to a solution increasing its the volume and decreasing the concentration of the solution. One can of orange juice concentrate will make four cans of orange juice Pearson Education, Inc. Chapter 8, Section 1 35

36 Dilution Although the addition of solvent increases the volume, the amount of solute doesn t change; it is the same in the concentrated solution and the diluted solution Pearson Education, Inc. Chapter 8, Section 1 36

37 Initial and Diluted Solutions In the initial and diluted solution, the moles of solute are the same, and the concentrations and volumes are related by the following equations: 2013 Pearson Education, Inc. Chapter 8, Section 1 37

38 Guide to Calculating Dilution Quantities

39 Learning Check What volume of a 2.00% (m/v) HCl solution can be prepared by diluting 25.0 ml of 14.0% (m/v) HCl solution? 2013 Pearson Education, Inc. Chapter 8, Section 1 39

40 Solution What volume of a 2.00% (m/v) HCl solution can be prepared by diluting 25.0 ml of 14.0% (m/v) HCl solution? Step 1 Prepare a table of the concentrations and volumes of the solutions. Analyze the Problem Pearson Education, Inc. Chapter 8, Section 1 40

41 Solution What volume of a 2.00% (m/v) HCl solution can be prepared by diluting 25.0 ml of 14.0% (m/v) HCl solution? Step 2 Rearrange the dilution expression to solve for the unknown quantity. Step 3 Substitute the known quantities into the dilution expression and calculate Pearson Education, Inc. Chapter 8, Section 1 41

42 Learning Check What is the molarity (M) of a solution prepared by diluting 10.0 ml of 2.7 M NaOH to 60.0 ml?

43 Solution What is the molarity (M) of a solution prepared by diluting 10.0 ml of 2.7 M NaOH to 60.0 ml? Step 1 Prepare a table of the concentrations and volumes of the solutions. Analyze the Problem Pearson Education, Inc. Chapter 8, Section 1 43

44 Solution What is the molarity (M) of a solution prepared by diluting 10.0 ml of 2.7 M NaOH to 60.0 ml? Step 2 Rearrange the dilution expression to solve for the unknown quantity. Step 3 Substitute the known quantities into the dilution expression and calculate Pearson Education, Inc. Chapter 8, Section 1 44

45 Solutions in Chemical Reactions When chemical reactions involve aqueous solutions, we use molarity and volume to determine the moles of the substances required or produced. Zinc reacts with HCl to produce ZnCl 2 and hydrogen gas H 2.

46 Guide to Calculations Involving Solutions in Chemical Reactions

47 Learning Check How many liters of 3.00 M HCl are needed to completely react with 4.85 g of CaCO 3?

48 Solution How many liters of 3.00 M HCl are needed to completely react with 4.85 g of CaCO 3? Step 1 State the given and needed quantities. Analyze the Problem.

49 Solution How many liters of 3.00 M HCl are needed to completely react with 4.85 g of CaCO 3? Step 2 Write a plan to calculate the needed quantity or concentration. mass molar moles mole mole moles molarity liters of CaCO 3 mass of CaCO 3 factor of HCl HCl of HCl

50 Solution How many liters of 3.00 M HCl are needed to completely react with 4.85 g of CaCO 3? Step 3 Write equalities and conversion factors including mole mole and concentration.

51 Solution How many liters of 3.00 M HCl are needed to completely react with 4.85 g of CaCO 3? Step 3 Write equalities and conversion factors including mole mole and concentration.

52 Solution How many liters of 3.00 M HCl are needed to completely react with 4.85 g of CaCO 3? Step 4 Set up the problem to calculate the needed quantity or concentration.