Solutions. Solutions Overview

Transcription

1 Solutions Chapter 9 Solutions Overview Terminology Units of Concentration Dilutions Colligative Properties 1

2 Terminology Solution- A homogenous mixture of two or more substances (ions or small molecules) Solvent- The component of the solution that has the same physical state as the final solution (I.e., a liquid still a liquid) If more than one component has this physical state, the one present in the largest amount is the solvent Solute- any component that is dissolved in the solvent Process of Solution Like dissolves like - solvent-solvent forces, solute-solute forces, and solvent-solute forces similar ΔH can be exothermic or endothermic 2

3 Amount of Solute Present Dilute Solution- a solution that contains only a small amount of solute per volume of solution Concentrated Solution- a solution that contains a large amount of solute per volume of solution Saturated Solution- A solution that contains the maximum amount of solute per volume of solution Solubility- The maximum amount of solute that will dissolve in a given amount of solvent at a specified temperature: usually g/100 ml Effect of Temperature on Solubility Variable depending on the compound Most increase solubility with increase in temperature 3

4 Units of Concentration Molarity (M) Weight/ Volume Percent (% w/v) Volume/Volume Percent (% v/v) Parts per Million (ppm) Molarity Molarity (M) - the number of moles of solute in 1.0 liter (or 1000 ml) of solution M = # mol of solute # liters of solvent Moles of solute = Molarity x Volume of solution Volume of solution = moles of solute Molarity 4

5 Molarity Calculations Flow diagram for conversions between molarity, moles and volume Weight/Volume Percent Concentration Weight/Volume Percent (%w/v) - the number of grams of solute in 100 ml(final volume) of solution Often used for solutions of a solid in a liquid Examples: Saline solution 0.90% (w/v) NaCl Intravenous glucose solution - 5.0% (w/v) Eye wash solutions % (w/v) boric acid 5

6 Volume/Volume Percent Concentration Volume/volume Percent (%v/v)- the number of ml of solute in 100 ml of solution Example: Blood alcohol content % (v/v) to be legally drunk as an adult 0.020% (v/v) legal limit for minors 0.025% (v/v) after one beer, one wine or one shot for a 150 pound male (80% less for females and 10% more/less per 15 pounds plus/minus) 0.05% (v/v) all sensory systems are impaired; Parts per Million Parts per million (ppm)- one part of something in a million parts (10 6 ) Mass of solute (g) x 10 6 Mass of solution (g) Volume of solute (ml) x 10 6 Volume of solute (ml) Milligrams solute liter of solution 6

7 Equivalents of Ions One equivalent (Eq) - the molar mass of the ion divided by its charge Examples: 1 Eq Na + = 23.0g/+1 = Eq Mg 2+ = 24.3/+2 = Eq HPO 3 2- = 80.0/-2 = 40.0 Milliequivalents (meq) - 1/1000 of an equivalent Useful for concentrations of blood electrolytes (meq/l) see Table 9.6 Dilutions General Dilution Formula: C f x V f = C i x V i Where C is any concentration unit, V is any volume unit, f is the final state and i is the initial state. The equation is rearranged to find the missing component if the other three are known. 7

8 Electrolytes Electrolyte- a substance that produces ions in water allowing for the conduction of electricity Strong electrolyte- substance that ionizes completely Weak electrolyte- a substance that ionizes only partially Nonelectrolyte- a substance that does not produce ions Colligative Properties Colligative Properties- Properties that depend only on the concentration of solute particles in a solution, NOT on the nature of the particles The freezing point of a solution decreases as the concentration of solute particles is increased (antifreeze) Each mole of solute lowers the f.p. of 1 kg of water by 1.86 o C. The boiling point of a solution increases as the concentration of solute particles increases (coolant) Each mole of solute raises the b.p. of 1 kg of water by 0.51 o C Osmosis- Flow of water molecules through a semi-permeable membrane from a solution having a lower solute concentration to one having a higher solute concentration 8

9 Osmosis Terminology Osmolarity (osmol)- the number of moles of all solute particles in 1.0 L of solution 0.2 M glucose = 0.2 osmol 0.2 M KCl = 0.4 osmol Osmotic pressure- the amount of pressure to to push the water back through the semipermeable membrane Osmosis Revealed 9

10 Osmosis and Biological Systems Isotonic Solution- A solution that contains the same concentration of solute particles found in cellular fluids 0.9% (w/v) or 0.15 M NaCl = physiological saline 5% (w/v) or 0.28 M glucose (dextrose) solution Hypotonic Solution- A solution that contains a solute particle concentration less than that found in cellular fluids Hypertonic Solution- A solution that contains a solute particle concentration greater than that found in cellular fluids Effects of Osmotic Pressure 10

11 Dialysis Remove small undesired components from a solution, e.g., hemodialysis 11