Properties of Solutions Part B Liquid Solutions clear

Properties of Solutions Part B

Liquid Solutions: -clear & transparent -colorless or colored Colloids: solute particles are large enough to scatter light particles (>1 nm)Tyndall effect -true solutions do not scatter light -colloids are solutions that do not settle out -examples: fog, smoke, whipped cream, mayonnaise, gelatin Suspensions: mixtures with larger particles -suspensions will settle -particles can be filtered out -examples: muddy water, calamine lotion

Tyndall Effect The light-scattering phenomenon In the Tyndall effect, light passes through solution, but light is scattered when it passes through colloid. Scattering of Light in a Colloidal Dispersion vs. a True Solution In the Tyndall effect, light passes through solution, but light is scattered when it passes through colloid. true, clear solution Colloid solution

Table 8. 4 - Property Comparison for Solutions, Colloidal Dispersions, and Suspensions Copyright © 2016 Cengage Learning. All Rights Reserved.

Colligative Properties A property of a solution that depends only on the number of dissolved particles (concentration of solute), not on their chemical identity. § Colligative Properties: a) Vapor Pressure Lowering b) Boiling Point Elevation c) Freezing Point Depression d) Osmotic Pressure

Vapor-Pressure Lowering • Adding a nonvolatile solute to a solvent lowers the vapor pressure of the resulting solution below that of the pure solvent at the same temperature Figure 8. 11 - Surface of Liquid Solvent (a) Before and (b) After Addition of Solute Copyright © 2016 Cengage Learning. All Rights Reserved. 6

Vapor Pressure Lowering • Lowers the vapor pressure of a solvent. – Lower vapor pressure means that fewer water molecules can escape from the liquid phase into the gas phase at given temperature. Remember, a lower vapor pressure means a higher boiling point! • 2) Raises the boiling point of a solvent.

Boiling Point Elevation • Nonvolatile solute elevates the boiling point of the solvent. • The figures below illustrate how the vapor pressure of water is affected by the addition of the non-volatile solute, Na. Cl. 1. 0 M Na. Cl solution - microscopic view. Normal boiling point = 101. 0 o. C. Note that the ionic solid, Pure water - microscopic view. Na. Cl, produces Na+ ions (blue) and Cl- ions (green) Normal boiling point = 100. 0 o. C. when dissolved in water.

Freezing Point Depression • Adding a nonvolatile solute to a solvent lowers the freezing point of the resulting solution below that of the pure solvent • Freezing point depression and is related to the concentration of the solute. • Freezing or boiling temperature depends on the nature of the solvent, not on the identity of the solute.

Applications-Freezing Point Depression Adding rock salt to a slurry of ice and water lowers the temperature at which water freezes. – salting icy roads – making ice cream – antifreeze • cars (-64°C to 136°C) • fish & insects A lot of heat has to be removed for the water in cream to solidify.

De-icing of Airplanes is Based on Freezing-Point Depression Deicing agents are compounds made up of the chemical glycol and water. Glycol lowers the freezing point of the solvent, water

Example 1: Consider of three different solutes present in solution of the same concentration: a) 1 mole of Glucose C 6 H 12 O 6 (molecular) b) 1 mole of Na. Cl (ionic) c) 1 mole of Ca. Cl 2 (ionic) Answer: The strongest effect on colligative properties will have Ca. Cl 2 a) 1 mole glucose produces 1 mole of particles b) 1 mole Na. Cl produces 2 moles particles: Na. Cl→ Na+ + Clc) 1 mole Ca. Cl 2 produces 3 moles particles: Ca. Cl 2→ Ca+ + 2 Cl- Example 2: Consider of two different solutions with different concentration on boiling point: a) 5 M glucose – 5 moles b) 3. 3 M Na. Cl – 3. 3 x 2 = 6. 6 moles Answer: The increase of the boiling point depends on the number of moles of particles per 1000 grams of water. C 6 H 12 O 6 is a molecular substance. So, 5 mole of glucose is dissolved in 1000 grams of water, contains 5 mole of molecules; Na. Cl is an ionic substance. So 3. 3 mole of Na. Cl produces 3. 3 mole of Na+1 ions and 3. 3 mole of Cl- 1 ions. The solution contain 6. 6 moles of ions per 1000 g of water.

Example 3. Which of the following solution will have a lower freezing point than a solution containing 0. 20 glucose per kilogram solvent? a) Solution of 0. 10 mole of Na. Cl b) Solution of 0. 10 mole of Mg. Cl 2

Osmosis • The passage of a solvent through a semi-permeable membrane separating a dilute solution (or pure solvent) from a more concentrated solution – Semi-permeable membrane: A membrane that allows certain types of molecules to pass through it but prohibits the passage of other types of molecules Copyright © 2016 Cengage Learning. All Rights Reserved.

Figure 8. 13 - An Illustration of the Process of Osmosis Copyright © 2016 Cengage Learning. All Rights Reserved.

Osmotic Pressure The pressure that must be applied to prevent the net flow of solvent through a semipermeable membrane from a solution of lower solute concentration to a solution of higher solute concentration Copyright © 2016 Cengage Learning. All Rights Reserved.

OSMOLARITY • Used to compare the osmotic pressures of solutions • i is the number of particles produced from the dissociation of one formula unit of solute Calculate the osmolarity of the following solution: a) 2 M Na. Cl - Na. Cl → Na+ + Cl- Osmolarity=2 M x 2=4 osmol b) 2 M Ca. Cl 2 - Ca. Cl 2 → Ca 2+ + 2 Cl- Osmolarity=2 M x 3=6 osmol c) 2 M of Glucose – will not dissociate i=1 so Osmolarity=2 M x 1=2 osmol d) 2 M of Na. Cl and 1 M glucose – when two solutes are present the collective effect of both solutes must be considered; Osmolarity=1 M x 1(glucose) + 2 M x 2 (Na. Cl)= 5 osmol

Osmosis In osmosis, there is net movement of solvent from the area of higher solvent concentration (lower solute concentration) to the are of lower solvent concentration (higher solute concentration). Water tries to equalize the concentration on both sides until pressure is too high.

Isotonic Solution A solution with an osmotic pressure that is equal to that within cells A cell placed in an isotonic solution. The net movement of water in and out of the cell is zero because the concentration of solutes inside and outside the cell is the same.

Hypotonic Solution A solution with a lower osmotic pressure than that within cells Cell in a hypotonic solution In a hypotonic solution, the concentration of solutes outside of the cell is less than that inside. There is a net flow of water into the cell, causing the cell to swell and perhaps to burst.

Hypertonic Solution A solution with a higher osmotic pressure than that within cells Cell in a hypertonic solution In a hypertonic solution, the concentration of solutes outside the cell is greater than that inside. There is a net flow of water out of the cell, causing the cell to dehydrate, shrink, and perhaps die.

A cell in an: isotonic solution hypertonic solution

Table 8. 5 - Characteristics of Hypotonic, Hypertonic, and Isotonic Solutions Copyright © 2016 Cengage Learning. All Rights Reserved.

Two aqueous solutions are separated by a semi permeable membrane. Red blood cell fluids, physiological saline solution is 5 % (m/v) glucose water are all isotonic with respect to one another.

Saline solution • Saline solution for intravenous infusion. 0. 90% w/v of Na. Cl • Red blood cell fluid, physiological saline solution and 5 %(m/v) glucose water are isotonic with respect to one another. The white port at the base of the bag is where additives can be injected. The port with the blue cover is where the bag is spiked with an infusion set.

Practice: If you add 2. 6 g of sodium chloride (molar mass = 58 g/mole) to 300 m. L water, what is the molarity, percent (m/v), and osmolarity of this solution? a. 0. 15 M, 0. 9%, and 0. 30 osmol

Isotonic Solutions – same osmotic pressure Hypotonic Solutions — lower solute concentration Hypertonic Solutions — higher solute concentration How Osmosis works http: //highered. mcgrawhill. com/sites/0072495855/student_view 0/chapter 2/animation__how _osmosis_works. html Would red blood cells shrink, swell, or stay the same when placed in each of the following solutions. Calculate the molarity and osmolity for each of those solution. a) 2. 3% (m/v) glucose b) 5 % Ca. Cl 2 solution