Chem 107, week of 3/22 and 3/24
Chem 107, week of 3/22 and 3/24 Chem 107
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This 6 page Class Notes was uploaded by Kelly Johnson on Sunday March 27, 2016. The Class Notes belongs to Chem 107 at West Chester University of Pennsylvania taught by Jacqueline Butler in Winter 2016. Since its upload, it has received 15 views. For similar materials see General Chemistry for Health Science in Chemistry at West Chester University of Pennsylvania.
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Date Created: 03/27/16
Chemistry Notes 3/22 and 3/24 1. Liquids and Solids Continued a. The Solid State i. Properties 1. Highly organized 2. Fixed shape and volume 3. Incompressible 4. Melting point depends on strength of the attractive forces 5. Crystalline- Has a regular and repeating structure 6. Amorphous- In a disordered state, no organized structure ii. Types of Crystalline Solids 1. Ionic a. Strong electrostatic forces hold them together b. Extremely high melting and boiling points c. Hard and brittle properties d. Dissolves in water (electrolytic) e. Ex. NaCl 2. Covalent a. Held together only by covalent bonds b. High melting and boiling points c. Extremely hard d. Bond in a network e. Ex. Diamonds 3. Molecular a. Held together by intermolecular forces b. Often soft c. Have a low melting point d. Often volatile e. Ex. Ice or graphite 4. Metallic a. Metal held together with metal bonds, not covalent bonds b. Metal Bonds i. Overlapping orbitals ii. This causes high electron density where electrons are extremely mobile. iii. Allow for conductivity c. Valence electrons are delocalized, meaning they are located around the outside (“sea of electrons”) iii. Sublimation 1. The process in which a liquid converts directly to a gas, without stopping in the liquid phase 2. Ex. Dry ice 2. Properties of Solutions a. Definition i. The components of a mixture are uniformly intermingled, making it homogeneous ii. Can be liquids, solids, or gases b. Terms i. Solution- homogeneous mixture ii. Solute- substance in lesser quantity iii. Solvent- substance in higher quantity iv. Aqueous Solution- solution in which the solvent is water c. Examples i. Air and alloys such as brass d. Intermolecular Forces of Solutions i. As the solution forms, the solvent pulls the solute particles apart and surrounds them ii. The forces that form are strong enough to compete with the forces between the solute or solvent particles themselves e. When a Solute Dissolves i. There are attractive forces between solute particles holding them together. There are also attractive forces between solvents. ii. Once combined, forces form between the solute and solvent. If this force is strong enough, the solute will dissolve f. Factors affect solubility i. “Like dissolves like” ii. There must be similar forces in both the solute and the solvent for the substances to be able to dissolve g. General Properties of Liquid Solutions i. Clear, transparent, with no visible particles ii. May have color iii. Electrolytes are formed from solutes that are soluble ionic compounds, and nonelectrolytes do no dissociate iv. Volumes of solute and solvent are not additive v. Ex. Sugar vs salt water 1. Salt is ionic so it will dissociate 2. Sugar is molecular so it will not dissociate 3. Colloids a. Colloidal Suspensions i. Suspended particles that are unevenly distributed in a medium ii. Particles are slightly larger so they can be seen when a light is shown through, but not to the naked eye 1. If particles are smaller than 1 nm, it is a solution 2. If particles are between 1 nm and 1000 nm, it is a colloid 3. If particles are larger than 1000 nm, it is a precipitate b. Tyndall Effect i. The ability of a colloidal suspension to scatter light 4. Degree of Solubility a. Definition i. Solubility describes how much of a particular solute can dissolve in a certain solvent at a specific temperature b. Factors that Affect i. Polarity of a solvent and solute (forces involved) 1. The more polar, the lower the solubility ii. Temperature 1. Increase in temperature leads to increase in solubility iii. Pressure 1. Very little effect if any c. Levels of Saturation i. Saturated 1. The solution contains as much solute that can be dissolved at a certain temperature ii. Unsaturated 1. More solute can be added at that temperature iii. Supersaturated 1. Solvent holds more solute than is normally possible at that temperature 2. Must be heated, solute added, and then cooled slowly d. Solubility and Equilibrium i. If excess solute is added, some dissolves ii. Rate of dissolution is faster at first iii. Precipitation occurs quickly later on iv. Saturated Solution is at dynamic equilibrium 1. Rate of dissolution is equal the rate of precipitation e. Henry’s Law i. The number of moles of a gas dissolved in a liquid at a given temperature is proportional to the partial pressure of the gas above the liquid ii. Directly proportional to the pressure of the gas in the atmosphere in contact with the liquid iii. Gases are more soluble at low temperatures and it greatly decreases at higher temperatures f. Concentration Based on Mass i. Concentration is the amount of solute dissolved in a given amount of solution ii. The concentration may have an effect on physical and chemical properties g. Solution Composition i. Mass/Volume percent mL of solution x100 1. ¿ massof solute(g) ¿ ii. Mass/mass percent massof solute(g) x100 1. massof solution(g) iii. Parts per thousand (ppt) massof solute(g) 1. x1,000 massof solution(g) iv. Parts per million (ppm) massof solute(g) 1. massof solution(g)x1,000,000 *** iii and iv are often used for very dilute substances 5. Concentration in Molarity (M) a. What? i. Molarity is the number of moles of solute in one liter of solution amountof solute(mol) ii. Molarity(M)= volumeof solution(L) b. Dilution of Solutions M1V 1=M2V 2 i. 1. M= molarity 2. V= Volume c. Molality i. Solute concentration is expressed in mole-based units ii. Molality is described as the moles of solute per kg of solvent ***** WILL NOT NEED TO KNOW HOW TO CALCULATE d. Concentration- Dependent Solution Properties i. Colligative Properties 1. Dependent on the concentration of the solute particles 2. Include: a. Vapor pressure lowering i. Raoult’s Law 1. When solute is added, vapor pressure decreases in proportion to the concentration 2. The solvent molecules serve as a barrier to the solvent molecules trying to escape, resulting in a decreased vapor pressure b. Boiling point elevation i. If a solute is present, boiling point must be raised in order to raise the vapor pressure to atmospheric temp ii. Proportional to the number of solute particles 1. An electrolyte will have a higher effect than a nonelectrolyte iii. ΔT= K b solute 1. K b Molal boiling point elevation constant 2. m= molality of a solute 3. i= van’t Hoff factor (moles of particles) c. Freezing point depression i. Solute molecules interfere with the rate at which liquid water molecules associate to form the solid state ii. Proportional to the number of solute particles iii. ΔT= K f solute 1. K f molal freezing point depression constant 2. m= molality of the solute 3. i= van’t Hoff Factor (moles of particles) d. Osmotic pressure i. Some membranes have small pores that allow particles to pass through them based on size ii. Semipermeable membranes- allow solvent but not solute to diffuse from one side to another iii. Osmosis is defined as the passage of solvent from a dilute solution to a more concentrated solution 1. Pressure is required to stop this flow iv. Is the solutions on both sides of the membrane are the same, the solutions are known as isotonic e. Tonicity and the Cell i. Crenation 1. When a cell is placed in a solution that has a higher solute concentration (hypertonic) than the cell itself, water will rush out of the cell causing the cell to collapse. This is known as crenation 2. Pickling a cucumber uses this process ii. Hemolysis 1. When the cell is placed in a solution of lower concentration (hypotonic) than the cell itself, water will rush into the cell causing it to burst/lyse iii. Isotonic 1. When the cell is place in a solution of its same concentration, there will be equal flow between sides and the cell is happy f. Aqueous Solutions i. Water is known as the “universal solvent” and is an excellent solvent for polar molecules. Water is also the most abundant liquid on earth. (60% of the human body is water) g. Biological Effects of Electrolytes in Solution i. Cations + + 1. Na and K are the two most important cations 2. They move across the cell membrane via active transport 3. If Na is too high or too low, the body reacts a. Low: Decreased urine output, dry mouth, flushed skin, fever b. High: confusion, stupor, coma 4. If K is too high or too low, it often results in death by heart failure ii. Anions - 1. Cl helps maintain acid/base balance, osmotic pressure, and Oxygen transport by hemoglobin 2. HCO is the form in which most CO2 exits the body 3 iii. Proteins 1. Act as blood clotting factors, antibodies, and albumins 2. Transported as a colloidal suspension 3. Transport nutrients and waste products