Content review MB mB/ nB cB nB/ V nB cB·V 1. Molar mass (摩尔质量) def mB/ nB g•mol-1 2. Molarity（摩尔浓度） cB def nB/ V mol•L-1 nB cB·V specify the formula!

Exercises Choice: which of the following is NOT an SI base unit? A kg B s C L D K 2. How many atoms are there in 5 moles of sulphur atoms? A 1.20*1023 B 3.01*1023 C 6.02*1023 D 3.01*1024 3. One drop of water weitghs 0.040 g. How many molecules are there in one drop, taking the molar mass of water as exactly 18.0 g.mol-1? A 1.3*1021 B 2.4*1022 C 3.3*1023 D 3.9*1022 C D A

4. What are the units of molarity? A mol.kg-1 B g.mol-1 C mol.L-1 D none 5. How many moles of hydrochloric acid are present in 0.80 L of a solution with a concentration of 0.40 mol.L-1? A 0.32 B 0.50 C 0.80 D 2.0 Fill in the blanks: 6. A 4.00 mol.L-1 solution of H3PO4 will contain ( ) g of (M=97.99 g.mol-1) in 0.250 L of solution. C A

cd cc·Vc / Vd Dilution of Concentrated Solution When a solution is diluted, the volume is increased by adding more solvent and the concentration is decreased, but the total amount of solute is constant. n = cc·Vc = cd ·Vd = n Example 3 Calculation of Molarity of a Dilute Solution What is the molarity of a solution of KCl that is prepared by dilution of 855 mL of a 0.475 mol•L-1 solution to a volume of 1.25 L? cd cc·Vc / Vd 0.475*0.855 / 1.25 0.325 mol•L-1

Chapter 2 Colligative Properties of Solutions(稀溶液的依数性) Introduction Injection of a hypertonic solution into the blood stream will cause crenation, while a hypotonic solution will cause hemolysis. Why? Solution Concentration Vapor pressure lowering Colligative properties Boiling point elevation Freezing point depression Osmosis and osmotic pressure

Key points: To relate the osmosis and osmotic pressure to the concentrations of solution To calculate osmotic pressure of electrolytes and nonelectrolytes To understand the importance of osmosis in medicine

New Words osmolarity 渗透浓度 electrolyte 电解质 shen tou nong du isotonic 等渗的 deng shen de hypotonic 低渗的 di shen de hypertonic 高渗的 gao shen de electrolyte 电解质 nonelectrolyte 非电解质 fei dian jie zhi osmosis 渗透 osmotic pressure 渗透压 shen tou ya semipermeable membrane半透膜 ban tou mo

2.4 Osmosis and Osmotic Pressure of Solutions （溶液的渗透与渗透压） Experiment: On the left is a pure solvent, and on the right, a solution. The two are separated by a semipermeable membrane. As a result, the water level rises on the right and drops on the left.

Term: Semipermeable membrane -Certain membranes allow solvent molecules to pass through them but not solute molecules. Osmosis -When a solution and its pure solvent are separated by a semi-permeable membrane, the pure solvent will diffuse through the membrane and dilute the solution. This process is known as osmosis.

Problems Why? Solvent molecules can pass through the membrane in both directions, but the concentration of water is larger in the pure water, more water molecules strike the membrane per second on that side, and more water moves into the solution than leaves it.

Problems If a solution of lower C and a solution of higher C are separated by a semi-permeable membrane, will there be the osmosis? Why? Concentrated solution Dilute solution Semipermeable membrane

Problems Problems Condition ? Direction ? a semipermeable membrane Concentrated solution Dilute solution Semipermeable membrane a semipermeable membrane solutions of different C on either side of the membrane Problems Direction ? from a solvent system to a solution system from the solution of lower C to the solution of higher C

2.4.2 Osmotic pressure（渗透压） Term: The amount of pressure that must be exerted just to prevent net transport of solvent across a semipermeable membrane is the osmotic pressure. Symbol: π Unit: Pa (kPa)

Problems How to calculate the osmotic pressure ? Π = cB RT Van’t Hoff equation： the gas constant 8.314 J • K-1 • mol-1 the absolute temperature, K Osmotic pressure kPa Π = cB RT Molarity of solutions mol• L-1

1:1 NaCl→ Na++Cl- total m = 2 cB 1:2 CaCl2→ Ca2++ 2Cl- total m = 3 cB Attention: cB is the total molarity of all the dissociated solute species present. Nonelectrolyte(非电解质): total molarity =cB Electrolyte (电解质): total molarity = i cB 1:1 NaCl→ Na++Cl- total m = 2 cB 1:2 CaCl2→ Ca2++ 2Cl- total m = 3 cB

Nonelectrolyte (非电解质) Example1 When 2.00 g of sucrose (蔗糖，C12H22O11) is dissolved in 50.0 mL of water solution, what is the osmotic pressure at 37℃? 解：

Π ＝ i cBRT Electrolyte (电解质): Π ＝ i cBRT Example 2 The 9.0 g ·L-1 salt (NaCl) solution is called physiological saline. What is the osmotic pressure at 37℃? 解： Π ＝ i cBRT

Content review Osmosis (渗透) definition, condition, direction, semipermeable membrane 2. The osmotic pressure （渗透压） Electrolyte: Π = cB RT Nonelectrolyte: Π = i cB RT

Exercises Choice: Colligative properties depend on A the chemical properties of the solute B the chemical properties of the solvent C the number of particles dissolved D the molar mass of the solute 2. Which of the following is NOT a colligative property? A the boiling point of a solvent B the freezing point depression C the vapor pressure lowering D the osmotic pressure C A

3. The molarity of human blood is 0. 30 mol. L-1 3. The molarity of human blood is 0.30 mol.L-1. what is the osmotic pressure of blood at 25 ℃? A 1486.5 kPa B 62.8 kPa C 371.6 kPa D 743.3 kPa 4. Which of the following aqueous solutions should have the highest osmotic pressure? A 0.010 mol.L-1 sucrose at 15 ℃ B 0.010 mol.L-1 NaCl at 15 ℃ C 0.010 mol.L-1 CaCl2 at 15 ℃ D 0.010 mol.L-1 CaCl2 at 50 ℃ D D

True or false: 1. The osmotic pressure of a solution is the exerted pressure needed to prevent net transport of solvent across a semipermeable membrane that separates the solution from the pure solvent. 2. At the given temperature, the osmotic pressure of 0.015 mol.L-1 NaCl (aq) is higher than that of 0.010 mol.L-1 CaCl2 (aq) . 3. A semipermeable membrane is a kind of selective membrane. Usually, they allow solvent molecules to pass through them but not solute molecules. T F T

Calculation What is the molar mass of albumin if 100.0 mL of a solution containing 2.00 g of albumin has an osmotic pressure of 0.717 kPa at 25 ℃? solution:

red blood cells in different concentration solutions 2.4.3 Importance of Osmosis (osmotic pressure) in medicine Why？ physiological saline Less than 9 g/L more than 9 g/L red blood cells in different concentration solutions

cos nos/ V 2.4.3.1 Osmolarity(渗透浓度) Term: osmotically active substances（渗透活性物质）：In body fluids, there are ions, small molecules, and large molecules. All these substances have an osmotic effect. osmolarity -the total molarity of osmotically active substances cos def nos/ V

cos def nos/ V Example 3 What is the osmolarity of (1) 0.278 mol ·L-1 glucose (C6H12O6) solution and (2) 0.154 mol ·L-1 salt (NaCl) solution ?

Example 4 The 0. 4 mol. L-1 glucose (C6H12O6) solution 1L and 0. 2 mol Example 4 The 0.4 mol.L-1 glucose (C6H12O6) solution 1L and 0.2 mol.L-1 salt (NaCl) solution 1L are mixed with each other. What is the osmolarity of the final solution?

2.4.3.2 isotonic, hypertonic and hypotonic sulutions Standard: blood plasma hypotonic isotonic hypertonic 280 mmol.Ｌ-1 320 mmol.Ｌ-1 Terms: Isotonic: two solutions with the same  separated by a semipermeable membrane. Hypertonic: having a higher osmotic pressure Hypotonic: a solution of lower  than a isotonic solution.

Isotonic solution: 0.9% (9g/L) NaCl Red blood cells: osmolarity = 0.306mol/L 0.9% (9g/L) NaCl osmolarity = 2×9g/L /58.5g/mol =0.306mol/L Red blood cells normal.

Hypotonic solution: 0.5% (5g/L) NaCl Red blood cells: osmolarity = 0.306mol/L 5g/L NaCl: osmolarity = 0.171mol/L Hemolysis (溶血): red blood cells placed in a hypotonic solution (relative to intracellular solution); there is a higher solute concentration in the cell; osmosis occurs and water moves into the cell. The cell bursts.

Hypertonic solution: 1.5% (15g/L) NaCl Red blood cells: osmolarity = 0.306mol/L 15g/L NaCl: osmolarity = 0.513mol/L Crenation（血栓）: red blood cells placed in hypertonic solution (relative to intracellular solution); there is a lower solute concentration in the cell than the surrounding tissue; osmosis occurs and water passes through the membrane out of the cell. The cell shrivels up.

Conclusion: For intravenous feeding, it is necessary that the nutrient solution have exactly the osmotic pressure of blood plasma. If it does not, the blood cells may collapse or burst as a result of osmosis. To prevent crenation or hemolysis, solutions must be isotonic. Range of Isotonic Solution: 280 ~ 320 mmol·L-1 Isotonic Solution: physiological saline solution (9g/L NaCl), 50g/L glucose Standard: blood plasma

Problems Examples of osmosis? Limp carrot placed in water becomes firm because water enters via osmosis. Salty food causes retention of water and swelling of tissues (edema). Water moves into plants through osmosis. Salt added to meat or sugar to fruit prevents bacterial infection (a bacterium placed on the salt will lose water through osmosis and die) Cucumber placed in NaCl solution loses water to shrivel up and become a pickle.

Summary cB nB/ V Π = i cB RT 【key points】 1. Molarity- Molar Concentration (摩尔浓度，物质的量浓度) 2. Osmosis and Osmotic Pressure （渗透与渗透压） 3. isotonic, hypertonic and hypotonic sulutions 【homework】 p20 T2 p39 T6，T9 cB def nB/ V Π = i cB RT