1. Chapter 14 Section 14.2 Solution Concentration

2. Solution Concentration
The concentration of a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution
Concentrations can be measured qualitatively and quantitatively.
Qualitatively using the words:
1- concentrated: contains a large amount of solute.
2- dilute: contains a small amount of solute

3. Concentration Description
Types of Mixtures
Quantitatively using one of the following concentration ratios
Concentration Description
Ratio
Percent by mass
mass of solute × 100
mass of solution
Percent by volume
volume of solute × 100
volume of solution
Molarity
moles of solute
liter of solution
Molality
kilogram of solvent
Mole fraction
moles of solute + moles of solvent

4. percent by mass:
Q1: In order to maintain a sodium chloride (NaCl) concentration similar to ocean water, an aquarium must contain 3.6 g NaCl per g of water. What is the percent by mass of NaCl in the solution?3.5%
Q2: You have g of a bleach solution. The percent by mass of the solute sodium hypochlorite (NaOCl) is 3.62%. How many grams of NaOCl are in the solution?54.3g
Q3: The percent by mass of calcium chloride in a solution is found to be 2.65%. If 50.0 g of calcium chloride is used, what is the mass of the solution? g

5. Percent by volume
Q1: What is the percent by volume of ethanol in a solution that contains 35 mL of ethanol dissolved in 155 mL of water?18%
Q2: What is the percent by volume of isopropyl alcohol in a solution that contains 24 mL of isopropyl alcohol in 1.1 L of water? 2.1%
Q3: If 18 mL of methanol is used to make an aqueous solution that is 15% methanol by volume, how many milliliters of solution is produced? 120 mL

6. Molarity
Q1: A mL intravenous (IV) solution contains 5.10 g of glucose (C6 H12O6). What is the molarity of this solution? The molar masses are, C=12’H=1’O=16 g/mol of glucose M
Q2: Calculate the molarity of 1.60 L of a solution containing 1.55 g of dissolved KBr. (K=39,Br=80) M
Q3: How much calcium hydroxide (Ca(OH )2), in grams, is needed to produce 1.5 L of a 0.25M solution? (Ca=40,O=16,H=1).28g

7. Step 3: Distilled water is added to the flask to bring the solution level up to the calibration mark Step Step Step3
How to prepare an accurate solution?
Step 1: The mass of the solute is measured.
Step 2: The solute is placed in a volumetric flask of the correct volume.

8. Questions
Q1: How many grams of CaCl2 would be dissolved in 1.0 L of a 0.10M solution of CaCl? 11g
Q2: How many grams of CaC l2 should be dissolved in mL of water to make a 0.20M solution of CaC l?11g

9. Dilution Equation
concentrated solution can be diluted by adding solvent. The number of moles of solute does not change when a concentrated solution is diluted.
Dilution Equation:
M1 V 1 = M2 V 2
M1 and V1 represent the molarity and volume of the stock solution, and M2 and V2 represent the molarity and volume of the dilute solution.

10. Questions
Q1: What volume, in milliliters, of 2.00M calcium chloride (CaC l ) stock solution would you use to make 0.50 L of 0.300M calcium chloride solution? 75ml
Q2: If 0.5 L of 5M stock solution of HCl is diluted to make 2 L of solution, how much HCl, in grams, was in the solution? 91.15g

11. Molality
Q1: In the lab, a student adds 4.5 g of sodium chloride (NaCl) to g of water. Calculate the molality of the solution. 0.77mol/Kg
Q2: What is the molality of a solution containing 10.0 g of N a2SO4 dissolved in g of water? m
Q3: How much (Ba (OH)2), in grams, is needed to make a 1.00m aqueous solution? 171g

12. Mole fraction
Mole fraction: the ratio of the number of moles of solute in solution to the total number of moles of solute and solvent.
Q1: What is the mole fraction of NaOH in an aqueous solution that contains 22.8% NaOH by mass? 0.118
If the mole fraction of sulfuric acid ( H2SO4) in an aqueous solution is 0.325, how much water, in grams, is in 100 mL of the solution?43.8%

13. Questions
Q1:Explain the similarities and differences between a 1M solution of NaOH and a 1m solution of NaOH.
Both solutions contain NaOH (solute) dissolved in water (solvent). The 1m solution contains 1 mole of NaOH per kilogram of water; the 1M solution contains 1 mole of NaOH per liter of solution.

14. End of section 14.2