Final study guide
Final study guide CHM 113
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This 12 page Study Guide was uploaded by Barbi Della Polla on Sunday February 1, 2015. The Study Guide belongs to CHM 113 at University of Miami taught by Leslie Knecht in Winter2015. Since its upload, it has received 264 views. For similar materials see General Chemistry 1 lab in Chemistry at University of Miami.
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Date Created: 02/01/15
FINAL CHM 113 Safety 0 Always wear goggles and closed toe shoes 0 Never pour water into an acid 0 Sodium bicarbonate is in the hood to take care of chemical spills Always put your plug for your hot plate back where you got it 0 Always ask where to dispose of chemicals 0 Eating and drinking are prohibited 0 Students may not enter in the lab without the TA 0 Only authorized experiments 0 Hot plates are never to be turned up past the setting 4 Usually 3 o For base spills boric acid and water Lab 1 Logger Pro Logger Pro is a program design to make laboratory measurements simpler and more accurate by using a computer to aid in data collection Used in the time based collection mode Collected for 180 seconds 0 Alcohol evaporation OCts The temperature decreases when the alcohol evaporates because when a liquid is evaporated absorbs energy and cools its surroundings This is an endothermic reaction because heat was absorbed O 20 4O 6O 80 100 120 140 160 180 200 Freezing Point of Lauric Acid put the LA test tube to melt scale of LabPro is set to 600 s The melting point is the at portion of your graph 435 0C Melting point temperature solidliquid Freezing point temperature liquidsolid For pure substances the melting and freezing points are the same the difference is if the temperature rises or decreases density rectangle 2 mass Density of metal cylinder 2 Density irregular shapes 2 Supercooling the temperature of LA dip bellow the freezing point temperature and then rise back up to the freezing point just before the at portion of the curve 60 4O 20 O O 100 200 300 400 500 600 700 Lab 2 Density Density is the ratio of its mass to its volume Its an intensive physical property independent of the amount of mass and also the volume Relates info on how the atoms or molecules are arranged in space Water is denser than ice because of the arrangement of the particles Tighter packing stronger interaction between molecules Speci c gravity is the ratio of the density of the substance to the density of water Temperature 4 0C the usual reference temperature for the water maximum density 100gmL Intensive properties don t depend on the amount of matter present Extensive properties depend on the amount of water present Block of wood weigtlted balance v0lamebxaxh Regular shapes mass of the cylinder v0lameltVHr2h Rock mass spring balance volume mass E air mass 6 water gtlt density water 0 Plastic found by levitating the PVC in solution Added two solutions of Calcium chloride one is more dense than the PVC and the other is less dense If the solution is more dense than the plastic it will oat If the solution is less dense than the plastic it will sink Only works for things that are not soluble in the liquid If the plastic sinks add more of the concentrated solution If the plastic oats add more of the dilute solution mass cylinder with s0l mass cylinder density of plastic 2 volume of s0l Lab 3 Puri cation of Adipic Acid H2C6I I804 We used solubility intensive property to separate and isolate the acid from impurities Adipic acid is used for food avorings the synthesis of nylon 66 which will allow the manufacturing of carpet bers clothing tire reinforcements auto parts 22 million metric tonsyear are the worldwide production of Adipic acid Adipic acid requires nitric acid oxidation of compounds like cyclohexanol and cyclohexane both of which are synthesized by benzene lt emits nitrous oxide N20 that contributes to global warming 400 thousand metric tons of nitrous acid produced each year Slightly soluble in cool water very soluble in boiling water FA 4 Km 53 mil quot5 5 I I I 39 fail Sal In If mmeier no I III III GI Ea m 1 H fail l g E 1l 2 3 4 5 El 3 31 SCI Terrup ET Anthropogenic caused or used by humans Recrystallization technique used to purify chemicals By dissolving both impurities and a compound in an appropriate solvent either the desired compound and impurities can be coaxed out of the solution leaving the other behind V6COV Vy Charcoal used to removed oxidized compounds and ne carbon particles Fluted paper the numerous folds produce a larger surface area for contact with the solution leading to a more rapid rate of ltration We cannot pour the liquid into the center of the lter paper because it will break First ltration l removed oxidized compounds and ne carbon particles Without stirring Second ltration l ltered out the compounds that are soluble by letting those compounds go through the lter paper and your AA crystals stay in the lter paper ls important to let the Adipic acid dry in order to form the crystals Melting point is lower and broader than thee pure compound when impurities are present because disrupts intermolecular forces This value tells you how accurate the recrystallization was Melt Temp Percent recovery yield weight pare adipie acid obtained X 100 weight of crude adipie acid Start with Lab 4 Conductimetric Titration and Gravimetric determination of BaSO4 Determine the concentration of barium hydroxide Qualitative analysis what compounds or elements are present in a substance Quantitative analysis how much of a particular compound is present in a sample Acidbase and precipitation reaction Ba2 aq 20H39aq 2Haq SO4239aq l BaSO4s 2H20 Procedure for conductimetric add 0100 M H2504 slowly to BaOH2 and measure conductivity with conductivity probe Units of conductivity microseism per cm uScm The conductivity graph is V shaped conductivityvolume The end point is where not more titrant should be added Requirements for gravimetric analysis to work 1 The compound formed must be pure and of known stoichiometry 2 The precipitation reaction must be virtually complete that is the percent yield of the solid product should be 999 or better 3 The precipitation reagent should be speci c for the sample being determined interference by other types of compounds forming precipitates should be minimal 4 The solid that is precipitated should be in the form of reasonably large wellformed crystals This is necessary so that the precipitate can be easily ltered and the compound will have the highest possible purity 5 The molecular weight of the precipitated solid should be high enough that a reasonable weight of precipitate is generated when the weight percent of substance being determined is low in the unknown sample Flocculate cause to aggregate into a mass by heating the solution of precipitated barium sulfate just to boil Strontium mercury l and lead ll could interfere and co precipitate Common ions don t interfere 0 Caution Sulfuric acid is a strong acid The barium hydroxide solution is caustic avoid spilling Crucible in the oven in order to dry the precipitate if we don t put it in the oven a higher content of sulfate will be present CALCULATIONS 1 Given the concentration of sulfuric acid this will be equal to the concentration of barium hydroxide at the equivalence point Conductimetric titration 2 Gravimetric Determination you get the moles of barium sulfate from the mass of the precipitate mass crucible and precipitate mass crucible mW of barium sulfate Remembering that this number of moles is equal to the moles of barium hydroxide at the equivalence point 3 Then use the formula M1 V1 M2 V2 to calculate the concentration of barium hydroxide Lab 5 Types of reactions Visual indicators precipitation color change bubbles Nonvisual indicators temperature and conductivity Conductivity ability of a substance to conduct electricity 1ohms Higher concentration of ions higher conductivity Small ions are slightly better conductors than larger ions Higher charged ions are solvated so their conductivity ef ciency is slightly decreased ie Mg is better than Na but not twice as good Endothermic chemical reaction that absorbs heat Exothermic chemical reaction that release heat Used Lab Pro events with entry the keep bottom Combustion always gives water and co2 1 HCI aq H20 l H30aq Cl39aq 2 H30aq Cl39aq Naaq OH39aq l H20 Naaq Cl39 aq Net ionic eq OH39aq H l H20 Spectators ions Na and Cl Acidbase reaction In the graph the conductivity will increase until the 20 drops of HCI when start to decrease adding NaOH until almost 40 and the goes up again due to an excess of NaOH Endpoint occurred in the drop 40th same number of drops added of the acid and base therefore the same concentration 3 RedoxPrecipitationDouble displacement NH4 OH39aq Cu2 NO339aq l NH4aq NO339aq CuOHs Net ionic 2 OH39aq Cu2aq l CuOHs Spectators ions NH4 N03 Conductivity increased as we added 20 drops of NH3 stayed the same as we started to add CuNO32 Change in color blue 4 Gas evolution Na2C03Aq HClaq l H20 C02g 2 Naaq C03239aq 2Haq 2Claq l 2Naaq 2Claq H2C03 H20 C02 Net ionic CO3239aq 2Haq l H20 C02g The conductivity decreases along the 45 drops of HCI 5 Precipitation and double displacement NaCIaq KNO3 aq KCaq NaNO3aq Naaq Cl aq Kaq NO3aq No reaction The conductivity increased when adding the KN03 but not too much 6 Precipitation and double displacement Na2SO4 BaN022 BaSO4s 2NaN02aq Net ionic Baaq SO4aq I BaSO4s H20 Spectators ions Nitrate and sodium The conductivity decreases when the drops of NaZSO4 Adding the barium nitrate the water became fuzzy 7 Redox FeCl3 SnC2 2 Fe3 Sn2 l Fe2 Sn3 Redox Fe reduces Sn l oxidized FeCl3 l oxidizing agent SnC2 reducing agent 8 Redox gas evolution and displacement Mgs 2Haq 2Claq l Mgaq H20 2Claq Net ionic Mgs 2Haq l Mgaq H20 Spectator ion CI The conductivity started to increase because we were adding more hydrogen ions to the solution increased until 20 drops then at portion Lab 6 Acids and Bases Acids is a proton donor sour Bases proton acceptor bitter Litmus test natural dye sensitive to acids and bases Acids Bases 0 Universal indicator green pH 7 mixtures of dyes more sensitive than litmus papers But is more effective to use pH meter pH ogH pOHlogOH essentia the p of anything is the og of that thing pH7 is neutral pH lt 7 acidic pH gt 7 baisc 539 mm in J Baking soda 78 base Borax 884 base Washing soda 1034 base Vinegar 242 acid Ammonia 1156 base Coke 246 acid Root Beer 395 acid Salt 6 acid Tomato 55 acid Tap water 8 base Starch 65 acid Onion 65 base Sea water 8 base Sugar 85 base Club soda 6 acid Apple 55 acid Epsom sat 65 acid illu iilquot lpl Linn L Coke is more acidic than root beer because has greater amounts of phosphoric acid while Root Beer has citric acid less stronger C02 dissolves in water to make H2CO3 which makes for a more acidic solution Lab 7 Gas Laws Boyle s law at a constant temperature a xed amount of gas occupies a volume inversely proportional to the pressure exerted WTIMWE V l I Ve a on it Pli PVo Pressure F E a d 5mL onto the volume we read off your syringe be ave e you rLitre391 z In the experiment for Boyle s law syringe the temperature didn t hold constant because when you compress a gas it heads up and when it expands it cools But this change was negligible for our experiment Charles s Law at a constant pressure the volume occupied by a xed amount of gas is directly proportional to the absolute temperature VTinitial VT nal Absolute zero lowest obtainable temperature Kelvin a value of 273 OC 141i L2 3 n 32 1 h lnt a rum 9 ED ifinial ne irritj Hum my 4E a 313E c FIJI 105 ii Lilli Temperature Eli Used torr mm Hg 760 mm Hg 1 atm ln Charles s law experiment we used a glycerin plug to trap a small sample of air between the plug and the bottom of the pipet Maintaining constant pressure on the trapped air Assuming that the air trapped below the plug is constantly at atmospheric pressure lnvert the numbers reading the volumes Assume that is 0 instead of 05 04 was read as 01 Raise temperature to 90 and dropped to 5 degrees in 5 degrees before we kept the data Lower temperatures than 50 we put ice chips Stirr to make the temperature uniform Absolute zero b y mx b mwww 17 If PVnRT Lab 8 Gas Laws ll 0 Equivalent weight that weight of a substance which will react with or produce one mole of hydrogen Loose or gain of electrons for redox or one mo of hydrogen atoms for acid base reaction Mgs 2HCLaq D MgCI2aq H2g MgO might be present but you have to clean the mg ribbon from any oxide coating or impurities Causing errors in our results more mass You CANNOT add water into acid but in this experiment you do it because we are using concentrated HCI which is more dense than pure water creating a layer between them Ah height of water mm is recorded to calculate the pressure of the water Pw Ah136 136 mm H20 1 torr Dry gas pure gas Without anything else 112 L 1 equivalent of water STP standard temperature 273K and pressure 1 atm PexVex P Stp Vstp Tex The numbers of equivalents of hydrogen will be the same as the magnesium The equivalent weight of Mg gr Mg of Equiv Error theoretical value experiment values experiment value x 100 The theoretical values are obtained by dividing the MW over the valence T Stp PWV Pg dry gas Pb Pw Lab 9 Freezing Point Depression Lauric Acid Water less dense than ice because of the intermolecular arrange in the water the molecules are more close to each other which makes it more dense rather the ice molecules have more space between them Impurities will lower the freezing point because the crystal lattice will be infringed Van t Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved and the concentration of a substance as calculated from its mass We didn t use it because we worked with a nonelectrolyte molecule covalent 39 msolute Molality n solute Kg solvent We used molality because mass is not affected when a change of temperature occurs Your solvent for this experiment was auric acid Your solute was benzoic acid Two different amounts 075 g and 15 g benzoic acid Lauric acid was held constant in each at 800 g Heat of fusion the amount of heat required to convert a solid at its melting point into a liquid without an increase in temperature Bil MP la1i4i39lll flitfur alluramulj ummnz njrr EFLUIJ39LI EEEFIEIBFEI Ef if l CHEFE Lab 10 Determination of Ka of a weak acid Methods for determinate Ka 1 Measurement of the pH of a solution containing a known concentration of a weak acid 2 Measurement of the pH at the halfneutralization point in the titration of a weak acid with a strong base Assumption that HA Buffer l Henderson Hasselbach A amp o pHpka log Strong base with weak acid equivalence point above pH 7 Strong acid with weak base equivalence point below pH 7 Strong acid and base equivalent point pH 7 Ka acidity constant acid ionization constant higher ka s more stronger the acid will be Equivalence point the moles of titrant added are equal to the moles of analyte present base and acid E l Jilin Indiana PH pH at 12 pka EEIEgHgihlE di erente in Valiume I quot h Khan 3 PH 9 15 Equivalence m39m Hall anu lwlenme pain 39 a I i
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