Solutions and Colloids Homogeneous (or nearly homogeneous) Mixtures

Solutions Homogeneous mixtures Solvent = dissolving medium often liquid; frequently water gas in air and other gas solutions rarely a solid Solute(s) = dissolved material(s) solids, liquids, and/or gases often more than one solute

Water as Solvent Form aqueous solutions Many biological fluids are solutions or have solution components One of best solvents for dissolving ionic substances Poor solvent for non-polar covalent substances.

Water O “H-bonding” binds water molecules tightly. H O H H O O H O H + - “H-bonding” binds water molecules tightly. H O - + O H + - O H + - O H -

Water Water is one of best solvents for ionic material (electrolytes) Water’s polar molecular structure interacts strongly with charged ions Water---Ion attractions replace ion---ion and water---water attractions with little net energy change

Water Crystal’s +/- attractions cause lattice energy, which must be overcome to break up crystal. Na+ Cl-

Water Na+ Cl-

Water “Void” weakens crystal and makes it more likely to break up in vicinity. Several more H2O molecules may associate Na+ Cl-

Water Na+ Cl-

Water Na+ Cl-

Water Note: Positive ions associate with negative ends of waters, and negative ions associate with positive ends of waters. +/- forces release energy Na+ Cl-

Water In similar fashion, the entire crystal dissolves positive ions link to oxygen of water negative ions link to hydrogen of water process call hydration Hydration releases energy Hydration energy compensates for lattice energy.

Water

Water An exothermic dissolving process. Hydration energy is greater than lattice energy.

Water

Water An endothermic dissolving process. Lattice energy is greater than hydration energy.

Water Exothermic processes release energy Temperature of surroundings increase. Hydration energy grater than lattice energy. Endothermic processes absorb energy. Temperature of surroundings decrease. Lattice energy greater than hydration energy.

Solution Concentrations Dilute Small amount of solute for given solvent Concentrated Large amount of solute for given solvent Saturated Maximum amount of solute for given solvent But these terms are qualitative, not quantitative, and are open to interpretation.

Solution Concentrations 20 gal. .

Solution Concentrations . Dilute or Concentrated???

Solution Concentrations . . Dilute or Concentrated???

Solution Concentrations It depends, of course, on one’s point of view. It’s only a teaspoon in 20 gallons. Dilute?? But this concentration is far beyond the lethal dose for the fish. Concentrated???

Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: grams Amount of solute Concentration = Total amount of solution (%, w/v) mL

Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: mass (grams) Amount of solute Concentration = Total amount of solution (%, w/w) mass unit (grams)

Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: mg Amount of solute Concentration = Total amount of solution ( mg %) dL

Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: moles Amount of solute Concentration = Total amount of solution ( molarity, M) Liters

Solution Concentrations % Concentration has multiplier of 100 to place ratio on “parts per 100” basis: Grams of solute mL of solution %, w/v = X 100

Solution Concentrations ‰ Concentration has multiplier of 1000 to place ratio on “parts per 1000 total” basis: Grams of solute mL of solution ‰ = X 1000

Solution Concentrations ppm concentration has multiplier of 106 to place ratio on “parts per million total” basis: Grams of solute mL of solution ppm = X 106

Solution Concentrations Practice situation: 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the % (w/v) concentration of this solution? Grams of solute mL of solution %, w/v = X 100 4.75 g % = X 100 = 0.633 % 750 mL The g/mL units are understood but not included.

Solution Concentrations 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the % (w/v) concentration of this solution? 0.633% NaCl The concentration is 0.633 % (w/v). 750 mL

Solution Concentrations Another: 12.5 grams of H2SO4 is dissolved in sufficient water to make 0.500 liters of solution. What is the % (w/v) concentration of this solution? Grams of solute mL of solution %, w/v = X 100 Solution volume units must be converted from liters to mL before doing calculations: 0.500 L = 500 mL. 12.5 g % = X 100 = 2.50 % 500 mL The g/mL units are understood but not included.

Solution Concentrations Once known, the solution concentration works as a conversion factor. Establishes the “relationship” between amount of solute and volume of solution. For % (w/v) concentrations, conversion factors derive from this relationship: “%-Value” grams of solute = 100 mL solution

Solution Concentrations Once known, the solution concentration work as a conversion factor. Examples (all are wt/vol percents): 0.85 % NaCl means… 0.85 g NaCl = 100 mL solution and the conversion factors are… 0.85 g NaCl 100 mL solution 0.85 g NaCl 100 mL solution or

Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What mass of NaCl is present in 2000 mL of 0.85% NaCl solution? 0.85% NaCl How much dissolved NaCl is in this 2000 mL of saline solution?

Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What mass of NaCl is present in 2000 mL of 0.85% NaCl solution? 0.85 g NaCl 100 mL solution 2000 mL soln X = 17.0 g NaCl

Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What mass of NaCl is present in 2000 mL of 0.85% NaCl solution? 0.85% NaCl 17.0 grams of dissolved NaCl is present in 2000 mL of this solution

Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What volume of 0.85% NaCl solution should contain 2.50 grams of dissolved NaCl? 0.85% NaCl What volume will contain 2.50 grams of dissolved NaCl?

Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What volume of 0.85% NaCl solution should contain 2.50 grams of dissolved NaCl? 0.85 g NaCl 100 mL solution 2.50 g NaCl X = 294 mL soln

Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): What volume of 0.85% NaCl solution should contain 2.50 grams of dissolved NaCl? 0.85% NaCl 294 mL of this solution contains 2.50 grams of dissolved NaCl.

Solution Concentrations Three types of calculations dealing with concentrations: Given the amount of solute and total solution, determine the concentration. Given the concentration and amount of solution, find the amount of solute. Given the concentration and the amount of solute, determine the amount of solution.

Solution Concentrations Three types of calculations dealing with concentrations: 2 Concentration = Amount of solute Total amount of solution 3 1

Solution Concentrations Given any two, be able to calculate the third: 2 Concentration = Amount of solute Total amount of solution 3 1

Solution Concentrations Molarity M = Moles of solute Liters of solution 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the molarity of NaCl in this solution? We previously determined this solution to be 0.633%; what is its molarity?

Solution Concentrations Molarity M = Moles of solute Liters of solution The 4.75 grams of NaCl will need to be converted to moles before the calulations are done. Similarly, to make units match, the 750 mL will be converted to liters.

Solution Concentrations Molarity M = Moles of solute Liters of solution 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. M = ? 58.5 g NaCl 1 mole NaCl 4.75 g NaCl X = 0.0812 mole NaCl 1000 mL 1 Liter 750 mL X = 0.750 L

Solution Concentrations 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. M = ? M = Moles of solute Liters of solution 0.0812 mole NaCl 0.750 L M = 0.0812 moles NaCl 0.750 Liters of solution = 0.108 M NaCl = 0.108 moles NaCl/L

Solution Concentrations 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the % (w/v) concentration of this solution and what is its molarity? 0.633% 0.108 M NaCl The concentration is 0.633 % (w/v) and… is 0.108 M 750 mL

Solution Concentrations Given any two, be able to calculate the third: 2 Concentration = Amount of solute Total amount of solution 3 1

Solution Concentrations Using the concentration as a conversion factor: Examples (all are wt/vol percents): How many moles of NaCl is present in 2000 mL of 0.225-M NaCl solution? 0.225M NaCl How much dissolved NaCl is in this 2000 mL of saline solution?

Solution Concentrations Using the concentration as a conversion factor: How many moles of NaCl is present in 2000 mL of 0.225-M NaCl solution? 1 L 1000 mL 0.225 moles NaCl 1 L solution 2000 mL soln x x = 0.450 moles Or… 0.225 moles NaCl 1000 mL solution 2000 mL soln x = 0.450 moles NaCl

Solution Concentrations Using the concentration as a conversion factor: What volume of 0.225-M NaCl solution will contain 0.0175 moles of dissolved NaCl? 1 L 0.225 Moles 1000 mL 1 L 0.0175 moles x x = 77.8 mL Or… 1000 mL solution 0.225 moles NaCl 0.0175 moles NaCl x = 77.8 mL soln

Solution Stoichiometry Just as grams of a pure substance and its FW determine moles of the substance, so do volulme and molarity of a substance in its solution. As for “pure substance” stoichiometry, solution stoichiometry usually involves a three-step approach:

Solution Stoichiometry Consider reaction of 0.200-M HCl with sodium carbonate: 2HCl + Na2CO3  2NaCl + CO2 + H2O 25.0 mL ? g Use volume and HCl molarity Use moles and FW of Na2CO3 ? moles ? moles Use Equation Coefficients How many grams of Na2CO3 will react with 25.0 mL of 0.200-M HCl solution?

Solution Stoichiometry Consider reaction of 0.200-M HCl with sodium carbonate: 2HCl + Na2CO3  2NaCl + CO2 + H2O 25.0 mL ? g Use volume and HCl molarity Use moles and FW of Na2CO3 ? moles ? moles Use Equation Coefficients 1000 mL HCl 0.200 mole HCl 2 mole HCl 1 mole Na2CO3 106 g Na2CO3 1 mole Na2CO3 25.0 mL HCl x x x = 0.265 grams Na2CO3

Solution Stoichiometry Consider reaction of 0.200-M HCl with sodium carbonate: 2HCl + Na2CO3  2NaCl + CO2 + H2O ? mL 5.00 g Use moles and HCl molarity Use grams and FW ? moles ? moles Use Equation Coefficients What volume of 0.200-M HCl solution is required for reaction with 5.00 grams of Na2CO3?

Solution Stoichiometry Consider reaction of 0.200-M HCl with sodium carbonate: 2HCl + Na2CO3  2NaCl + CO2 + H2O ? mL 5.00 g Use moles and HCl molarity Use grams and FW ? moles ? moles Use Equation Coefficients 106 g Na2CO3 1 mole Na2CO3 1 mole Na2CO3 2 mole HCl 0.200 mole HCl 1000 mL HCl 5.00g Na2CO3 x x x = 472 mL HCl solution

Solutions vs Colloids Solution Colloids Solute particle are of ionic or molecular size (a few nm across) Transparent to ordinary light Stable unless solvent evaporated Colloids Solute (called “dispersed phase”) typically 1000 nm or more per particle Giant molecules (or “clumps” of smaller ones) Not totally transparent – Tyndall Effect Dispersed phase may separate out (similar to separation of mayonnaise).

Solutions vs Colloids The Tyndall Effect True Solution Colloidal Mixture

Solutions vs Colloids The Tyndall Effect True Solution Colloidal Mixture

Transmembrane Diffusion Solution (H2O + Solutes) Pure H2O Semipermeable membrane Only water passes through osmotic membranes and faster from the side on which water is more concentrated.

Transmembrane Diffusion Solution (H2O + Solutes) Pure H2O Semipermeable membrane Diffusion rates tend to equalize as flow continues.

Osmotic Pressure If applied pressure is too low, H2O flows into the region of higher solute concentration... “Down the concentration gradient” for H2O. P P Membrane Pure H2O H2O + Solutes

Osmotic Pressure P If applied pressure is too high, H2O flows into the region of lower solute concentration... Against the natural concentration gradient for H2O. --Reverse Osmosis P Membrane Pure H2O H2O + Solutes

Osmotic Pressure P Minimum pressure required to maintain equal flow rates (to prevent infusion of H2O). Proportional to solute concentration differences across membrane. P Membrane Pure H2O H2O + Solutes

Solutions vs Colloids Solution Solute particles are of ionic or molecular size Transparent to ordinary light Stable unless solvent evaporated May pass through dialytic, but not true osmotic, membranes Colloids Typically 1000 nm or more per particle Not totally transparent – Tyndall Effect May separate out Particles too large to pass through most membranes

Transmembrane Diffusion Mixture (H2O, Na+Cl-, protein) H2O NaCl more concen-trated here Pure H2O NaCl H2O more concentrated here Dialytic membrane Water and solutes pass down concentration gradient through dialytic membrane. Colloids do not cross membrane.

Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: Osmoles (total moles) Amount of solute Concentration = Total amount of solution ( Osmolarity, osM) Liters For certain solutes, osM will equal M.

Osmolarity Calculating Impact Total of molarities of all types of solute particles in the solution. For ionic solutes, the ions are separated; and each ion has a separate molarity to be totaled. Molecular solutes have same molarity and osmolarity, but each different solute needs to be included. Impact Osmolarity determines osmotic pressure Useful in determining net direction of H2O flow across membranes.

Osmolarity Solute, M Osmolarity 0. 25-M C6H12O6 (molecular) 0. 25-osM 0. 25-M NaCl (ionic) 0. 50-osM (0.25-M Na+ + 0.25-M Cl-) 0. 10-M CaBr2 (ionic) 0. 30-osM (0.10-M Ca+ + 0.20-M Br-) 0. 25-osM (0.10-M Fe3+ + 0.15-M SO42-) 0. 05-M Fe2(SO4)3 (ionic)

Transmembrane Diffusion Dialytic membrane 0.6 osM + 1% colloid 1.0 osM + 2% colloid A B H2O Cl- 0.2 osM Ca2+ C6H12O6 0.2 osM 0.6 osM 0.1-M NaCl 0.1-M CaCl2 0.1-M C6H12O6 1% starch 0.1-M NaCl 0.2-M CaCl2 0.2-M C6H12O6 2% starch 0.3 osM 0.2 osM 0.1 osM

Transmembrane Diffusion Dialytic membrane 0.6 osM + 1% colloid 1.0 osM + 2% colloid A B H2O Cl- Hypotonic Hypertonic Ca2+ C6H12O6 0.1-M NaCl 0.1-M CaCl2 0.1-M C6H12O6 1% starch 0.1-M NaCl 0.2-M CaCl2 0.2-M C6H12O6 2% starch Water flows into hypertonic fluid (where water is less concentrated).

Transmembrane Diffusion Arterial End “Head pressure” --High Venous End “Head pressure” --Low Tissue Cell Wastes Head pressure of heart “pushes” nutrients and water into cell (PBLOOD> POSMOTIC). Nutrients Hypertonic blood “draws” wastes into blood (POSMOTIC>PBLOOD) .

Solution Concentrations 4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. What is the % (w/v) concentration of this solution? 0.633% NaCl The concentration is 0.633 % (w/v). 750 mL