Chapter 8 Solutions

Chapter 8 Solutions 8.6Properties of Solutions

Solutions Solutions • contain small particles (ions or molecules) • are transparent • do not separate, even by filtration or through a semipermeable membrane • do not scatter light

Colloids Colloids • have medium-sized particles • cannot be separated by filtration • can be separated by semipermeable membranes • scatter light

Examples of Colloids

Suspensions Suspensions • have very large particles • settle out • can be separated by filtration • must be stirred to stay suspended Examples: blood platelets, muddy water, and calamine lotion

Solutions, Colloids, and Suspensions

Comparison of Solutions, Colloids, and Suspensions

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 1) solution 2) colloid 3) 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 2) colloid

Colligative Properties Colligative properties • are changes in the properties of a solvent when solute particles are added • depend on the number of solute particles in solution • involve the lowering of freezing point • involve an increase in the boiling point

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)

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 A 1000-g sample of water contains 0.50 mole of Na3PO4. What are the new freezing point (FP) and boiling point (BP) of the solution? 1) FP 1.86 °C; BP 100.52 °C 2) FP 3.72 °C; BP 101.04 °C 3) FP 7.44 °C; BP 102.08 °C

Solution A 1000-g sample of water contains 0.50 mole of Na3PO4. What are the new freezing point (FP) and boiling point (BP) of the solution? 2) FP 3.72 °C; BP 101.04 °C Na3PO4 3Na+ + PO43- 0.50 mole 1.5 moles 0.5 mole Total moles of solute = 2.0 moles FP = 0 °C – 2(1.86 °C) = 0 °C – 3.72 °C = –3.72 °C BP = 0 °C + 2(0.52 °C) = 0 °C + 1.04 °C = 101.04 °C

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

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 (continued) • 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 occuring • 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 • is known as a “physiological solution” • of 5.0% (m/v) glucose or 0.9% (m/v) NaCl is used medically because each has a solute concentration equal to the osmotic pressure equal to red blood cells

Hypotonic Solutions A hypotonic solution • has a lower osmotic pressure than red blood cells (RBCs) • has a lower concentration than physiological solutions • 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 • has a higher concentration than physiological solutions • causes water to flow out of RBCs • causes crenation (RBCs shrink in size)

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 1) isotonic 2) hypotonic 3) hypertonic A. ____ 2% (m/v) NaCl solution B. ____ 1% (m/v) glucose solution C. ____ 0.5% (m/v) NaCl solution D. ____ 5% (m/v) glucose solution

Solution Indicate if each of the following solutions is 1) isotonic 2) hypotonic 3) hypertonic A. _3_ 2% (m/v) NaCl solution B. _2_ 1% (m/v) glucose solution C. _2_ 0.5% (m/v) NaCl solution D. _1_ 5% (m/v) glucose solution

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

Solution When placed in each of the following, indicate if a red blood cell will 1) not change 2) hemolyze 3) crenate A. _1_ 5%(m/v) glucose solution B. _2_ 1%(m/v) glucose solution C. _2_ 0.5%(m/v) NaCl solution D. _3_ 2%(m/v) NaCl solution

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

Learning Check Each of the following mixtures is placed in a dialyzing bag and immersed in pure water. Which substance, if any, will be found in the water outside the bag? A. 10% (m/v) KCl solution B. 5% (m/v) starch solution C. 5% (m/v) NaCl and 5% (m/v) starch solutions

Solution Each of the following mixtures is placed in a dialyzing bag and immersed in pure water. Which substance, if any, will be found in the water outside the bag? A. 10%(m/v) KCl solution: KCl ( K+, Cl−) B. 5%(m/v) starch solution: None, starch is retained. C. 5%(m/v) NaCl and 5%(m/v) starch solutions: NaCl (Na+, Cl−) will be found in the water outside the bag, but the starch is retained inside the bag.

Chapter 8 Solutions