Thermal Chemistry

StudyBlue printing of Thermal Chemistry html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, font, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td { margin: 0; padding: 0; border: 0; outline: 0; font-size: 100%; background: transparent; } body { line-height: 1; } blockquote, q { quotes: none; } blockquote:before, blockquote:after, q:before, q:after { content: ''; content: none; } /* remember to define focus styles! */ :focus { outline: 0; } /* remember to highlight inserts somehow! */ ins { text-decoration: none; } del { text-decoration: line-through; } /* tables still need 'cellspacing="0"' in the markup */ table { border-collapse: collapse; border-spacing: 0; } /* end RESET */ .header { min-width:800px; } .logo { padding:6px 20px 2px 20px; margin:0; font-size:25px; font-weight:bold; 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-moz-border-radius: 5px; -webkit-border-radius: 5px; } .print-button a:hover { background-color:black; } .theNote .content { width: 8.0in !important; margin: 5px auto; padding:20px; background-color:white; } .theNote .header { border-bottom: 1px dashed #C8C8C8; font-size: 17px; padding: 0 0 10px; line-height: 19px; color: #00ADE1; min-width:500px; } .theNote .body { font-size: 14px; line-height: 19px; padding: 10px 0; } .theNote{ padding:6px 0; clear:both; background-color: rgb(200,200,200); } .theNote h3{ color: rgb(100,100,100); } .theNote h1, .theNote h3{ background-color:white; padding:2px 20px; width:8.0in !important; margin: 0 auto; font-size: 15px; } .theNote h1{ padding-top: 10px; font-size: 15px; } .theNote h1:first-child{ font-size: 20px; } .theNote h3 { font-size: 14px; font-weight: normal; } #options { border: 3px double #ccc; padding: 5px 12px; margin: 10px 50px 10px 20px; float: left; } #info { border-top: 1px solid #ccc; padding-top: 5px; font-style: italic; } li { margin: 5px 10px 5px 25px; } ul li { list-style: disc; } ol li { list-style: decimal; } img { border: 0; } table { clear: both; width: 100%; border: 1px solid #c5c5c5; border-width: 1px 0; margin: 0; page-break-after: always; } table#page { page-break-after: auto; } td { text-align: center; font-size: 12px; border-bottom: 1px dashed #c5c5c5; height: 1.75in; width: 50%; padding-left: 15px; } .leftside { border-right: 1px solid #cccccc; padding: 0 15px 0 0; } .bottom td { border-bottom: none; } .clearfix { clear:both; line-height:1px; height:1px; } img { max-width:80%; max-height:150px; margin:20px; } @media print {.header { display: none; } .content .header{ display:inherit; } table { border: 1px dashed #bbb; border-width: 1px 0; } .theNote{ background-color:white; } } Terms Heat - energy transferred from hot object to cold object, measured in joules or calories System - something we're interested in, not including surrounding, i.e. a solution Surrounding - anything that surrounds the system, i.e. beaker, air Endothermic - system absorbs heat from surrounding = COLD Exothermic - system receives heat from surrounding = HOT Calorimetry - the science of measuring the heat of chem reactions or phys changes Calorimeter - sealed reaction chamber which is immersed in a known quantity of water in an insulated vessel, the energy change can be measured by the temperature change of the water Activated Complex (Intermediate) - highest point in energy profile, transitional structure that exhibits properties of both reactions and products, produced by effective collision of particles (point on graph) Energy of the Complex - distance from 0 to Activated complex (y-value not x) Activation Energy - difference between beginning and complex/top, energy particles need to collide with in order to react Enthalpy Change, dH - change of heat under constant temp and pressure, from beginning Y to end Y Heat form of energy that does work measured w/ calorimeter measured in calories or joules Temperature scale to indicate direction of heat flow, heat flows from high to low measured w/ thermometer measured in Celsius/kelvin Relationship - Q(heat change) = C (specific heat) * M (Mass in grams) * dT (Change in temp.) Reaction Types Exothermic energy released Relative energy of reactants greater than rel. energy of products, Er > Ep Sign of dH is negative , i.e. dH = Hp - Hr OH --> O + H + Heat (heat on right side of EQ) Lower energy, more stable Endothermic energy absorbed Relative energy of reactants less than rel. energy of products, Er<Ep Sign of dH is positive , i.e. dH = Hp - Hr Heat + NH + NO -> NHO (heat on left side of EQ) more energy, less stable Specific Heat Specific Heat = the amount of energy required to raise the temperature of one gramp of a substance by one degree celsius, can be used to identify an unknown substance Tells how easily the temp of that substance can be changed, the higher it is the harder it is to change the temperature (copper changes quickly, good for pots) Measured in J/(g*C) Liquid water has highest specific heat, copper has lowest Hot and Cold Packs Breaking and making of chemical bonds which absorb or release heat Instant cold pack - when broken the salt ammonium nitrate dissolves in water and absorbs heat Salt dissolve - crystals separate into ions, lots of energy used to break ionic bonds meaning lots of energy is absorbed from the surroundings, water molecules then attach to charged ions The absorption of energy to break bonds makes this endothermic, surroundings lose thermal energy Reaction gets cold = reaction absorbs heat Energy in matches already stored in chemicals before you strike it Combustion - heat absorbed to break original bonds then new bonds formed which release heat, amount absorbed < amount released, overall heat is given off Instant hot packs are not vigorous exothermic reactions, slower rate and lower temp Heat Factory Pack - when exposed to air, chemicals inside oxidize which creates heat, process sped up by shaking the pack and circulating the oxygen throughout the pack = faster rusting of the iron because other chemicals make rusting conditions ideal, can only be used once Heat Solution Pack - As supercooled crystal slowly solidifies it gives off heat, phase change principle, can heat in boiling water to make the crystal supercooled again If a reaction is spontaneous means chance it will occur, new product will be formed Entropy - disorder, packs utilize this, move from state of order to disorder which drives the energy flow backwards (cold packs) Equilibrium Reversible Chemical Reaction - Equilibrium - state when concentration of reactants and products remains constant, doesn't change anymore Concentration of reactants does NOT have to equal the concentration of the product, but it may The reaction does not stop, forward and reverse reactions are still going on without changing the CONCENTRATION of the system Dynamic Equilibrium - state of dynamic balance in which rates of forward and reverse reactions are equal, the system (concentration) doesn't change with time Equilibrium Constant - if jA + kB = lC + mD then...K = [C] j [D] m / [A] j [B] k the concentration of the products to the power of their coefficients divided by the concentration of the reactants to the power of their coefficients At a given temp. it only changes with temperature and not other factors At a certain temp, for a reaction at equilibrium, a certain ratio of reactant and product concentrations has a constant value K Pure solids and liquids don't appear in K expression, just gas and aq The k for the reverse reaction is 1/K K only changes with temp. for a specific reaction, a catalyst can't change the value of k In aqueous phase, the concentration is molarity (mol / L) MICE = Mole ratio, Initial, Change, Equilibrium - Chart with moles of objects on top and MICE on the side Predict direction K> 1 - forward reaction favored K< 1 - reverse reaction favored K = 1 - reaction is at equilibrium La Chatleier's Principle - If stress is imposed on a system at equilibrium (must be @ equ) the position of the equilibrium will shift in a direction that tends to reduce that change Adding a catalyst or an inert gas to a system does not shift Adding any noble gas doesnt change anything Moves away from heat term when heated, towards when cooled Moves away from increased concentration, towards decreased Lowering pressure of system or increasing volume of it shifts to the side with more moles Increasing pressure of system or decreasing volume of it shifts to the side with less moles Increasing pressure OF A COMPOUND decreases concentration, shifts towards it Decreasing pressure OF A COMPOUND increases concentration, shifts away from it Concentration of something increases when the reaction moves towards the side containing it If moles on both sides of an equation are the same then changing pressure has no effect, can't go to a side with lower moles cause there isn't one Equilibrium Graph reactants start up and go down, products start at 0 and go up when reactions reach equilibrium there are reactants left in the system because if not then K = x / 0 which is impossible Equilibrium system just means when reactants are at a stable number, not 0 Entropy and Free Energy Entropy - measure of disorder/randomness in a reaction Reaction Rate is how fast it occurs, measured in Molarity / seconds Spontaneous - reaction is possible , no relationship to speed, not fast Free Energy - G = H - t*S Change in Free Energy (dG) - dG = dH - t*dS when dG is negative, reaction is spontaneous if dH + and dS opposite, not spontaneous if dH - and dS opposite, yes spontaneous dG = 0, equilibrium, no reaction occurs Forces behind a spontaneous reaction Entropy Enthalpy - if reaction releases heat, it is more likely to be spontaneous Entropy Relationships Gas - highest entropy, Liquid - medium, Solid - lowest entropy Mixture > Compound > Element More atoms = greater entropy Higher temperature = greater entropy, when particles are heated they have more kinetic energy and more chance to be chaotic and disordered Entropy increases if right-side has higher entropy than left Entropy decreases if left-side (reactants) has higher entropy than right Cannot be determined if one method suggests increasing and another suggests decreasing