8.6 Properties of Solutions General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Chapter 8 Solutions 8.6 Properties of Solutions Lectures © 2013 Pearson Education, Inc.

Mixtures: Solution, Colloidal Dispersion or Suspension Particle size, distribution and polarity help us to further classify mixtures as a solution, colloidal dispersion, or a suspension.

Solutions In a solution, the solute is dissolved as small particles that are uniformly dispersed throughout the solvent to give a homogeneous solution. the solute and solvent particles cannot be visually distinguished and the solution appears transparent. solute particles are so small that they go through filters and semipermeable membranes. Semipermeable membranes allow solvent and very small solute particles to pass through.

Colloids Colloids have much larger solute particles than solutions. are homogeneous mixtures that do not separate or settle out. have solute particles that pass through filters but not semipermeable membranes.

Examples of Colloids

Suspensions Suspensions are heterogeneous nonuniform mixtures. have very large particles that can be trapped by filters or semipermeable membranes. settle out soon after mixing. must be stirred to stay suspended. Examples of suspensions include medications, such as Kaopectate, calamine lotion, antacid mixtures, and liquid penicillin.

Comparing Solutions, Colloids, and Suspensions

Solutions, Colloids, and Suspensions Properties of different types of mixtures: (a) suspensions settle out; (b) suspensions are separated by a filter; (c) solution particles go through a semipermeable membrane, but colloids and suspensions do not.

Learning Check A mixture that has solute particles that do not settle out, but are too large to pass through a semipermeable membrane is called a A. solution. B. colloid. C. suspension.

Solution A mixture that has solute particles that do not settle out, but are too large to pass through a semipermeable membrane is called a B. colloid.

Colligative Properties are changes in the properties of a solvent when solute particles are added. depend on the number of solute particles in solution. lower freezing points. increase boiling points.

Freezing Point Lowering and Boiling Point Elevation When 1 mole of solute particles is added to 1000 g of water, the freezing point of water decreases by 1.86 C (from 0 C to –1.86 C). boiling point of water increases by 0.52 C (from 100 C to 100.52 C).

Freezing Point Lowering The salt CaCl2 used to melt ice on roads and sidewalks produces 3 moles of particles from 1 mole of CaCl2: 1 mole of Ca2+ and 2 moles of Cl−.

Electrolytes and Nonelectrolytes A solute that is a nonelectrolyte dissolves as molecules, whereas a solute that is a strong electrolyte dissolves entirely as ions. One mole of ethylene glycol, a nonelectrolyte dissolves in water, breaking up into one mole of molecules. One mole of calcium chloride, a strong electrolyte dissolves in water, breaking up into three moles of ions, one mole of Ca2+ ions and two moles of Cl− ions.

Moles of Particles The number of moles of particles depends on the type of solute. Nonelectrolytes dissolve as molecules. 1 mole of nonelectrolyte = 1 mole of particles in water Strong electrolytes dissolve as ions. 1 mole of electrolyte = 2 to 4 moles of particles in water

Effect of Solute Particles

Learning Check Identify the solution that will have a lower freezing point. A. 1 mole Ca(NO3)2 dissolved in 1 liter of water B. 1 mole KOH dissolved in 1 liter of water C. 1 mole C6H12O6 dissolved in 1 liter of water

Solution Identify the solution that will have a lower freezing point. A. 1 mole Ca(NO3)2 dissolved in 1 liter of water For every 1 mole of Ca(NO3)2, 3 moles of particles are produced, 1 mole Ca2+ and 2 moles NO3−. B. 1 mole KOH dissolved in 1 liter of water For every 1 mole of KOH, 2 moles of particles are produced, 1 mole K+ and 1 mole OH−. C. 1 mole C6H12O6 dissolved in 1 liter of water For every 1 mole of C6H12O6, 1 mole of particles are produced. Answer is A; it produces the largest number of particles.

Osmosis In osmosis, water (solvent) flows from the lower solute concentration into the higher solute concentration across a semipermeable membrane. the level of the solution with the higher solute concentration rises. the concentrations of the two solutions become equal with time.

Osmosis Water flows into the solution with a higher solute concentration until the concentration of both solutions are equal.

Example of Osmosis A semipermeable membrane separates a 4% starch solution from a 10% starch solution. Starch is a colloid and cannot pass through the membrane, but water can. What happens? semipermeable membrane 4% starch 10% starch H2O

Example of Osmosis The 10% starch solution is diluted by the flow of water out of the 4% solution, and its volume increases. The 4% solution loses water, and its volume decreases. Eventually, the water flow between the two becomes equal. 7% starch 7% starch H2O

Osmotic Pressure Osmotic pressure is produced by the solute particles dissolved in a solution. is the pressure that prevents the flow of additional water into the more concentrated solution. increases as the number of dissolved particles in the solution increases.

Learning Check A semipermeable membrane separates a 10% (m/v) starch solution (A) from a 5% (m/v) starch solution (B). If starch is a colloid, fill in the blanks in the statements below. 1. Solution ____ has the greater osmotic pressure. 2. Water initially flows from ___ into ___. 3. The level of solution ____ will be lower.

Solution A semipermeable membrane separates a 10% (m/v) starch solution (A) from a 5% (m/v) starch solution (B). If starch is a colloid, fill in the blanks in the statements below. 1. Solution A has the greater osmotic pressure. 2. Water initially flows from B into A. 3. The level of solution B will be lower.

Osmotic Pressure of the Blood Red blood cells have cell walls that are semipermeable membranes. maintain an osmotic pressure that cannot change without damage occurring. must maintain an equal flow of water between the red blood cell and its surrounding environment.

Isotonic Solutions An isotonic solution exerts the same osmotic pressure as red blood cells. of 5.0% (m/v) glucose or 0.9% (m/v) NaCl are examples of isotonic solutions. A red blood cell placed in an isotonic solution retains its volume because there is an equal flow of water into and out of the cell.

Hypotonic Solutions A hypotonic solution has a lower osmotic pressure than red blood cells (RBCs). causes water to flow into RBCs. causes hemolysis (RBCs swell and may burst).

Hypertonic Solutions A hypertonic solution has a higher osmotic pressure than RBCs. causes water to flow out of RBCs. causes crenation (RBCs shrink in size).

Isotonic, Hypertonic and Hypotonic Solutions In an isotonic solution, a red blood cell retains its normal volume. In a hypotonic solution, water flows into a red blood cell, causing it to swell and burst (hemolysis). In a hypertonic solution, water leaves the red blood cell, causing it to shrink (crenation).

Dialysis In dialysis, solvent and small solute particles pass through an artificial membrane. large particles are retained inside. waste particles, such as urea from blood, are removed using hemodialysis (artificial kidney).

Learning Check Indicate if each of the following solutions is A. isotonic. B. hypotonic. C. hypertonic. 1. ____ 2% (m/v) NaCl solution 2. ____ 1% (m/v) glucose solution 3. ____ 0.5% (m/v) NaCl solution 4. ____ 5% (m/v) glucose solution

Solution Indicate if each of the following solutions is A. isotonic. B. hypotonic. C. hypertonic. 1. ____ 2% (m/v) NaCl solution 2. ____ 1% (m/v) glucose solution 3. ____ 0.5% (m/v) NaCl solution 4. ____ 5% (m/v) glucose solution C B B A

Learning Check When placed in each of the following, indicate if a red blood cell will A. not change. B. hemolyze. C. crenate. 1. ____ 5% (m/v) glucose solution 2. ____ 1% (m/v) glucose solution 3. ____ 0.5% (m/v) NaCl solution 4. ____ 2% (m/v) NaCl solution

Solution When placed in each of the following, indicate if a red blood cell will A. not change. B. hemolyze. C. crenate. 1. ____ 5%(m/v) glucose solution 2. ____ 1%(m/v) glucose solution 3. ____ 0.5%(m/v) NaCl solution 4. ____ 2%(m/v) NaCl solution A B B C

Hemodialysis When the kidneys fail, an artificial kidney uses hemodialysis to remove waste particles, such as urea, from blood.