Study Guide: Lab Final
Study Guide: Lab Final CHEM-UA 125
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Popular in Chemistry
This 15 page Study Guide was uploaded by Brianda Hickey on Tuesday May 10, 2016. The Study Guide belongs to CHEM-UA 125 at NYU School of Medicine taught by Dr. Malgorzata (Margaret) Mandziuk in Spring 2016. Since its upload, it has received 204 views. For similar materials see General Chemistry I in Chemistry at NYU School of Medicine.
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Date Created: 05/10/16
Study Guide: Lab Final Tips for Lab Final: Be able to apply the calculations - Practice the ones you are most afraid of first Understand each step and why you are doing it Calorimetry, Stoicheoamerty, titration isvery important If a question gives you the option “not enough information to answer” - don’t be afraid to say no, sometimes you really don’t have enough information Don’t worry too much about safety lab Exp 2: Measuring Density of Liquids & Solids Overall Purpose: Measured the density of a solid made of an unknown metal, a rubber stopper, & several liquid solutions Background Information Extensive Property: Dependent on the quantity of substance (e.g., mass and volume) Intensive Property: Independent of quantity (e.g., density or index of refraction) Chemical Property: require chemical change to study Physical properties: can be observed by various methods without chemical change Density is an important intensive physical property of all substances Density will vary with temperature because volume changes with temperature Volume changes for solids/liquids = small Volume changes for gases = large Top Loading Balance higher capacity than analytical balance lower precision than analytical balance Analytical Balance great precision in a glass enclosure to minimize the eﬀect of air movement Density vs mass % Density is mass/volume, where mass % is (mass solute/mass solution) * 100 Units of Density kg/m^3 g/L lb/ft^3 kg/dm^3 General Procedure: Part I: massed diﬀerent salt in water solutions, determined vol, & found their density Part II: determined density of irregularly shaped objs Part III: determined density of irregularly shaped objs To ﬁnd the density: Regular shape: measure the mass & calculate the vol (D=M/V) Irregular shape: Displacement of water measure the mass of the object measure the volume of the object by displacement ﬁll a graduated cylinder with water Note the initial volume - Vi Place object in the graduated cylinder and note the ﬁnal volume - Vf The volume of the displaced water is the volume of the object [V = Vf - Vi] How to ﬁnd the mass of liquid: measure mass of graduated cylinder add liquid, measure mass again subtract mass of empty graduated cylinder For density measurements : use analytical balance % by mass = (mass of salt / mass of solution) x 100 Exp 3: Separation & Identiﬁcation of Food Dyes by Paper Chromatography Overall Purpose To separate and identify components of food dyes using food chromatography Background Information Chromatography – analytical separation technique that takes advantage of diﬀerences in attraction or aﬃnity btw solvent phase and components of a mixture chromatography is considered a physical separation Mobile Phase: a mixture is dissolved into a gas or liquid Stationary Phase: The mobile phase then moves over a solid component The components of the mix will separate based on their relative aﬃnities for either the mobile or stationary phase Aﬃnity for mobile phase move faster and farther along the stationary phase Aﬃnity for stationary phase move more slowly or over a shorter distance than mobile phase Aﬃnity for either phase is based on the structure and electrostatic forces of the components Polar molecule (a molecule with an unequal distribution of electric charge) = attracted to the more polar phase Systematic errors oﬀer when an instrument is consistently yielding a high or low value for a result a lab technician is erroneously making the same measuring mistake Types of Chromatography Gad-Liquid Chromatography: High Performance Liquid Chromatography Thin Layer Chromatography Paper Chromatography General Procedure: (Paper Chromatography) Stationary Phase: Sample to be separated is placed on chromatography paper Mobile phase: Paper is placed in a solvent Solvent is drawn up through the paper with capillary action (solvent moves up the paper because solvent is attracted to water molecules that are bound to the ﬁbers in the paper) The mix is then spotted a ﬁxed distance from the bottom edge of paper (origin line) Paper is placed in beaker with solvent and solvent is drawn up paper The leading edge of the solvent (solvent front) reaches the mixture the components will sep based on their aﬃnities for stationary or mobile Paper needs to be removed from the solvent before it reaches the top of the paper so you can measure the distance from the origin Th retention factor is a unites ratio that determines the relative aﬃnities of components for the solvent calc the retention factor = (Distance the analyze has traveled) / (Distance the solvent has traveled) Rf determines the aﬃnities of components of the solvent ~0 indicates strong attraction to stationary ~1 indicates strong attraction to mobile the solvent that gives the greatest diﬀerence in retention factors gives the greatest separation - resolution Dyes for Food, Drugs, and Cosmetics (FD&C) We used sodium salts of sulfuric acids ( or carboxylic acid in the case of red 3); this makes the dyes water soluble Must use pencil with chromatography if use a pen, the ink will run with the food dyes and ruin experiment If the origin line was marked with a pen, and not a pencil… the marks on the origin line would separate and elute, mixing with the dyes. We could not accurately determine Rf values Why do we want the ends to overlap when we all up our chromatograms? We don’t! We want them to touch but not overlap! If the beakers containing the solvents were not covered while running the experiment… the solvent could evaporate. If the solvent evaporated before the experiment was complete, we could not accurately determine the Rf values If the chromatogram was removed from the solvent after the solvent front had reached the top of the chromatogram paper…we would be unable to determine how far the solvent front traveled, and therefore could not determine the Rf for the components We are exporting the dyes polarity in order to separate the components of each dye If dyes have very similar Rf’s in most solvents: the structures of the two dyes are nearly identical Exp 4: Naming Inorganic Chemicals stock system – used to name inorganic chem compounds oxidation – loss of e- (takes place with reduction) positively charged metal ions – cations (get rid of e- and become positive) negatively charged non-metal ions – anions (accept e- and become negative) redox reactions – oxidation and reduction take place simultaneously species being oxidized – reducing agent species being reduced – oxidizing agent electronegativity of element (tendency to attract e-) determines type of bond ionic compounds – metal + nonmetal & e- are transferred from M à NM large diﬀ in EN covalent compounds – compounds where e- are shared btw NM + NM smaller diﬀ in EN assigning oxidation numbers: in free elements each atom has an oxidation # = 0 for monatomic ions it is = to the charge on the ion # for oxygen in most compounds is -2 (but in peroxides it is -1) # for hydrogen is +1 (but -1 w/ metal or boron in binary compound) ﬂuorine has # of -1 in a neutral molecule the sum of the #s of all the atoms = 0 in polyatomic ion the sum of the #s of all the atoms = ion’s net charge naming ionic binary compounds: metal + nonmetal (usually salts) cation names are metals named for element anion name is the name of the element but ending is –ide naming covalent binary compounds: e- are shared and are usually composed of just nonmetals use preﬁxes: mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca and use –ide for anion naming binary acids: -ide à hydro preﬁx + -ic ending ternary acids: per…ate à per…ic acid ….ate à ….ic acid ….ite à ….ous acid hypo…ite à hypo…ous acid hydrates: penthydrate (5H2O) so use preﬁx and then add it to hydrate Exp 5: Introduction to LabQuest Interface Overall Purpose to become familiar with LabQuest and learn data analysis The pH of a solution is the quantitative measure of acidity and is related to the H+ ion [H+] is the "molarity of H” and molarity means moles per liter of solution pH = -log [H+] Signiﬁcant ﬁgures when representing logarithms such as pH count only the digits to the right of the decimal point. The digit(s) to the left of the decimal is (are) related to the exponent Ex. pH = -log [1.0 X 10^(-7)] = 7.00 2 sig ﬁg General Procedure conduct volume measurements and titration Measure the temp and pH of the solutions pH – quantitative measure of acidity and is related to the hydronium ion (H+) concentration in the solution pH of pure water is 7.00 Molarity – moles per liter of solution [H+] can calculate the values by using: H+][OH-] = 1.0x10^-14 @ 25 C use the pH probe to evaluate acidity use the stainless steel temp probe for temp ﬁrst connect the probes to the interface & measure the temp & pH of solutions then conduct a titration to measure the temp & pH (measure of acidity) you add a base to acid titrations: ﬁll the buret to the zero mark with NaOHh put HCl in a beaker add NaOH until the equivalence point equivalence point: where moles of acid = moles of base usually reached at pH of 7 (because they have the same concentration) A meniscus is the curvature of the upper surface of a liquid in glassware due to tension forces acting between the glass and the liquid Parallax Error is the apparent displacement of an object as seen from two diﬀerent viewpoints that are not in line with the object. The meniscus must consistently be read at eye level Accuracy is the measure of how close the measurement is the actual measurement Exp 6: Back-Titration – Evaluation of Antacids Overall Purpose evaluating the eﬀectiveness of commercial antacids (use it when you have too much acid – basically it neutralizes the acid). To assess the neutralization capacity of a brand name antacid and evaluate its eﬀectiveness on the basis of it mass and its cost 2 types of bases are used in antacids: week bases or low-solubility strong bases, usually not very soluble in water Background Two types of bases are used in antacids Weak bases CaCo3 carbonates (CO3^(-2)) NaHCO3 bicarbonates (HCO3 - ) Low-Solubility strong bases Mg (OH)2 magnesium hydroxide Al (OH)3 aluminum hydroxide How can we determine the amount of base present in an antacid? we could dissolve a tablet to form a basic solution and then titrate with a standard acid but this approach has problems - we overcome these by back titrating Antacids are not very soluble in water (though they are soluble in acids) Antacids are usually weak bases that exhibit “buﬀering” capacity (resistance to pH change) while being titrated Back Titrate: Solves the problems of buﬀering and poor dissolution while allowing for the use of a strong acid/strong base add a known but excess amount of strong acid to completely neutralize the antacid tablet The base of the antacid is completely neutralized and stoichiometric amount of strong acid is neutralized We then titrate the remaining acid (excess) with standardized song base and indirectly determine how much acid had reacted A-B = N (A – moles of HCl added to antacid, N – moles of HCl neutralized, B – moles of HCl remaining after antacid reaction) Determine mass eﬀectiveness (E): E = N/W (N – moles of HCl neutralized, W – mass of antacid) Determine the cost eﬀectiveness (C): C = N/P (N – moles of HCl neutralized, P – price per tablet) Some acids dissolve very slowly eve in acidic solutions…you can heat the mixture to help them dissolve It is possible that some “ﬁller” material will not dissolve at all The indicator (bromophenol blue) is yellow in acidic solution After the reaction your solution will be acidic bc you added excess HCl. If it doesn’t turn yellow when you add the indicator then you didn’t add enough HCl(aq) According to the procedure, you will dissolve an antacid tablet into a speciﬁc amount of hydrochloric acid solution and then add an acid-base indicator. After the titration, the indicator should show the resulting solution is basic or neutral Exp 7: Qualitative Analysis Overall Purpose learn the behaviors of metal cation solutions with various reagents, using net ionic equations, perform qualitative analysis on a solution containing unknown mixture of metal cations Background Information Qualitative analysis = used to identify and classify matter Cations = positive ions (we will identify in the experiment) Anions = negative ions If a mixture is unknown, it is necessary to separate the components during the identiﬁcation process the chemical properties are determined by systematically exposing the unknown to number of reagents and observing the results Ionic compounds are more easily identiﬁed with their chemical properties When ionic compounds are dissolved in water -> the result is an aqueous solution containing the cations and anions of the dissolved compounds When two solutions are mixed and no visible reaction occurs, then we assume that all of the cation-anion combinations are soluble in the solution If a solid precipitate forms upon addition of a reagent, this would indicate the presence of a particular cation in the unknown Molecular Chemical Equation: all reagents and product species are present in their undissociated forms Total or complete ionic equation: the same as the molecular chemical equation, except that all aqueous species are given in their dissociated form Net ionic equation: a chemical reaction dealing with only the ions that are directly involved in the chemical reaction Spectator Ions: ions that are not directly involved in the reaction Complexation reaction: a chemical species called a complex ion or neutral complex is formed, resulting in a distinct color change occurs when a transition metal ion combines with either an anion or a polar neutral molecule In the experiment: use the ammonia and the thiocyanate ion to form a complex use Thiocyanate forms a complex with iron (III). The complex forms red solutions use ammonia to indicate the presence of copper (II) - will combine to form a brilliant plus solution General Procedure: We will identify the positive ions or cations (when ionic compounds are dissolved in water you get an aq solution containing the cations and anions of the dissolved compounds) To separate the precipitate form the solution you use: Filtration = utilizes a ﬁlter medium (ﬁlter paper) to separate the solid from the liquid centrifugation = uses centrifugal force for separation of mixtures more dense components of the mix migrate away from the axis while the less dense go towards the axis supernate – the solution which lies above the solid - poured oﬀ leaving the solid behind Exp 8: Chemistry & Thermodynamics Overall Purpose understand the concept of energy ﬂow in chem/phys rxns; determine calorimeter constant, speciﬁc heat/molar heat capacity of copper, heat of solution of ammonium nitrate, molar enthalpy of neutralization Background: Energy is how to measure the transfer of heat or capacity to do work look at the energy to determine if the chemical reaction will take place or not Some reactions lose energy (release), some rxns gain energy (absorb) exothermic = change in H < 0 = chemical reaction looses heat endothermic = change in H > 0 = chemical reaction absorbs heat First law of Thermodynamics: energy forms may change, but they are always conserved Energy is exchanged between systems & surroundings in 2 forms: Heat (q) amounts are determined through relation to temperature heat always ﬂows from a higher to lower temperature Work (w) w = force (F) x distance through which force is applied (d) The change in enthalpy = the heat exchanged at constant pressure measure of heat exchange per mole of reactant units = kj/mol Enthalpy (H) = a state function ( a thermodynamic quantity dependent only on its current state and not by how it got to that state) Molar enthalpy of neutralization: The heat released int eh neutralization of one mole of acid or base at constant pressure Calorimetry Calorimeter: an inﬂated container by carrying out the reaction within a calorimeter, no heat escapes and all heat is evolved or absorbed Calorimeter Constant: The amount of heat required to change the temperature of a content-pressure calorimeter by 1 degree Celsius It is necessary to determine cal (how much heat is absorbed by the calorimeter) for any accurate determination or energy transfer qsys=qsol+qcal+qrxn=0 Constant-pressure calorimetry the heat exchanged in the reaction is equal to the change in enthalpy change in H = -(qsol+qcal) Heat ﬂow in or out of system, q q = mc (change in T) m= mass, g c= speciﬁc heat, joules/g Celsius Change in T = Tf - Ti, Celsius General Procedure: Determine the speciﬁc heat and molar heat capacity of copper by using the calorimeter Determine the molar enthalpy of solution of an aq ionic salt Determine the molar enthalpy of neutralization Exp 9: Vitamin C Analysis – Redox Titration Overall Purpose standardize DCp (report avg conc and standard deviation), compare vit C content to the reported RDA, compare vit C content to the reported RDA Chemistry and Biology of Vitamin C Vit C is also known as ascorbic acid Oxidation = results in loss of e- Reduction = results in gain of e- Oxidation-reduction reaction (redox) = reducing agent is being oxidized an oxidizing agent is being reduced Transferred e- in any redox reaction have to be balanced the same as atoms on each side of the equation Ascorbic acid (AA) is a weak acid (so doesn’t ionize completely in water) and a reducing agent H+ ion concentration is relatively low as is the ascorbate ion The ascorbate ion acts as reducing agent, or antioxidant, to reverse oxidation and to remove potentially harmful oxidizing agents from the body James Lind studied vitamin C and its eﬀect on British sailors RDA means recommended daily allowance and for humans is 60mg of vitamin C Analysis of Ascorbic Acid use the oxidizing agent DCP in the analysis of AA DCP changes color when reduced to its reaction product leuco dye We will analyze AA in orange and grapefruit juices and in a vitamin C supplement tablet This titration, the pH will not change since this is an oxidation/reduction reaction or a redox titration As long as some AA solution remains, the blue DCP is reduced to colorless leuco dye Once the vitamin C is completely oxidized the DCP imparts a pink color to the solution End point = pink color To avoid any potential chemical interference, we add metaphosphoric acid (HPO3)n and a pH 3 buﬀer to the reaction mixture to achieve three goals 1. Metaphoric acid is used to denature and precipitate proteins from food or juice samples. Any proteins present would react with DCP and appear to be vitamin C 2. We willpower the pH to 3 so that side reactions of DCP with any species other than vitamin C are prevented 3. Also lowering the pH to 3 will inhibit the ionization and decomposition of vitamin C 2,6-dichloroindophenol serves as an indicator for the titration Why do we need to ﬁlter sample son juice and food products before titration?… to remove pulp and other solids from the solution Reducing agent in our reaction = ascorbic acid The metaphosphoric acid plays the role of precipitating proteins present in food in the vitamin C analysis Dehydroascorbic acid = an ascorbic acid oxidation product Ascorbic acid = oxidized in reaction DCP = reduced in reaction Leuco dye = a DCP reduction product Standardizing DCP Many important chemical reagents are extremely reactive - DCP is one of them …we must standardize before use To standardize: prepare a solution of known concentration of “reagent grade AA” (100% purity assumed), and then run the titration to the end point and calculate the concentration of the DCP by applying the known rules of stoichiometry Exp 10: Transition Metal Complexes & Beer’s Law Overall Purpose understand Beer’sLaw, calc the molar absorptivity, determine the conc of an unknown solution using beer’s law plot Background Information: Transition metals ions: Lewis acids which form stable acid-base reaction products known as complexes or coordination complexes Lewis acid: any species which accepts an electron pair Lewis base: any species that donates an electron pair Ligands: bases within complex formation that are ions or polar neutral molecules Solutions that absorb light in the visible region give rise to colored solutions What we see is the light that is not absorbed Solutions appear blue since blue light is not absorbed and passes through the solution The higher the concentration of the complex ion, the greater the light absorption and the more intense the blue color Can determine the concentration by comparing the color intensity to that of a standard solution of known concentration Absorbance is proportional to the path length or the distance the light travels through the sample Greater the path length the more complete the light absorption Absorbance is proportional to the molar absorptivity (function of a wavelength) is a constant for the experiment because we run the experiment at a ﬁxed wavelength. Absorbance is proportional to: Concentration, C (molarity) Path length, b (cm) Molar absorptivity, (1/Mcm) Plot of A vs C will yield a straight line with a slope of eb that passes through the origin Solutions will show deviations from Beer’s Law when they…transmit more than 90% of incident light and Transmit less than 10% of incident light Limitations of Beer’s law ^ The y -intercept of a Beer’s law plot is Zero The LabQuest Interface and Logger Pro software We use the LabQuest Interface colorimeter to measure the wavelength The reference or blank contains everything but the sample being studied Allows us to compensate for the extraneous absorption from the caveat, solvent, etc. which is subtracted when we calibrate the instrument Absorbance cannot be measured directly with LabQuest Interface, instead we measure % transmittance (%T) - how much light is not absorbed Absorbance simultaneously calculated and recorded A proper Beer’s Law plot…shows a linear relationship when plotting Absorbance vs. Concentration General Procedure: If we prepare several solutions with known concentration then write beer’s law A = ebC and plot A vs C we get a straight line and then use that to ﬁnd the concentration of the unknown sample Exp 11: Determining the Universal Gas Constant Overall Purpose studying ideal gases, measure the amount of O2 generated from the decomposition of H2O2, calculate the Universal Gas Constant Background Information PV = nRT (we are calculating R) Depending n T & P substances can exist as solids, liquids, or gases (the phase is determined by the strength of the intermolecular forces acting btw particles) Solid – molecules are held rigidly in place, so solid shape Liquid – particles are held closely together, but molecules slide past each other Gases – the particles are free to move without restraint Particles of a gas are far apart compared to their size The forces btw molecules diminish in strength w/ distance, the forces btw the particles are nearly negligible So gases expand when given the opportunity Highly compressive As the intermolecular forces btw particles become insigniﬁcant as the particles become so small that they barely collide so gases behave very diﬀ from each other Ideal gas = when intermolecular forces become more negligible then they can resemble ideal gases Boyle’s Law volume and pressure the pressure of a sample of gas held at constant temperature is inversely proportional to its volume P1V1 = P2V2 Charle’s Law gas temperature and volume for a ﬁxed sample of gas at a ﬁxed pressure, the volume of gas is proportional to its temperature V1/T1 = V2/T2 Gay-Lussac’s Law pressure and temperature held at constant volume -> pressure and temperature are directly proportional P1/T1 =P2/T2 Combined Gas Law a combination of the relationship determined by Charles, Gay-Lussac, and Boyle (P1V1)/T1=(P2V2)/T2 Avogadro’s Law volume and molecules Volume is inversely proportional to molecules V1/n 1= V2/n2 Ideal Gas Law PV=nRT R = .082057 Latm/molK General Procedure: Move the leveling bulb to make the pressure equal and then add yeast to cause a reaction and as the oxygen is released the water level will drop in the buret. Move the leveling bulb as the reaction runs so the water levels are basically equal then record volume, get the atmospheric pressure in the lab and the density of the hydrogen peroxide solution Use Oxygen to determine the value of the universal gas constant Yeast is used to catalyze the gas producing reaction It is important to have a gas tight apparatus for this experiment because a quantitative measure of gas generated is required The purpose of the leveling bulb is to allow us to equalize the pressure inside and outside the apparatus The pressure of the “ideal” gas in the apparatus is less than the pressure of the atmosphere because the “ideal” gas pressure is equal to the atmospheric pressure minus the water vapor pressure Oxidation-reduction is used to produce the “ideal” gas used in the experiment We will subtract PH2O2 from the atmospheric pressure Exp 12: Measuring Gas Evolution Overall Purpose measure gas evolution in a chem reaction, determine the stoichiometry of the reaction btw Mg and HCl Background Information This experiment involve the reaction of a measured amount of Mg with a known, but excess mahout of hydrochloric acid (HCl) -> react to form H2 gas Mg is oxidized (loses electrons) Hydrogen is reduced (gains electrons) Stoichiometry of reaction will be determined by: measuring gas evolution and back- titration Start w/ measured amount of Mg metal and add excess but known amount of HCl acid Assume Mg is the limiting reagent and reacts to completion So given the MM of the Mg metal we can determine the moles consumed in the reaction The vol of H2 gas evolved in the experiment displaces the same V of water from the container Using Dalton’s Law and Ideal Gas Law we use the amount of displaced water to calc the moles of H2 generated in the reaction After the Mg is consumed the mix is then titrated with standardized sodium hydroxide to determine the amount of unreacted HCl The moles of HCl were consumed in the reaction with Mg are calc by subtract the moles of unreacted HCl from initial moles of HCl Can use these molar amounts to determine the rations for the reaction of Mg with HCl Number of moles of any species consumed or evolved in a reaction is proportional to its coeﬃcient in the balanced chem eq We will determine the pressure due to the hydrogen gas using Dalton’s Law of Partial Pressures There are four pressures with which we must concern ourselves in this experiment. Which one of the following is related stoichiometrically to the amount of metal used?… The partial pressure of hydrogen in the ﬂask Role of sodium hydroxide…to determine the amount of excess hydrochloric acid remaining after the reaction with magnesium Measure the volume of hydrogen gas by determining the volume of water displaced by hydrogen gas Using the ideal gas law to calculate the n or hydrogen gas We need to adjust the water levels after the reaction to equalize the pressure inside and outside the ﬂask so that we can correctly determine the partial pressure of the hydrogen gas’ Exp 13: Separation by Fractional Crystallization Overall Purpose ﬁnding molar ratio (basically proving that the stoichiometric ratios given by the coeﬃcients in the equation are correct) Background Information Mixture = combo of two or more substances in which the substances retain their distinct identities Homogeneous = composition is uniform Solution = ex of a homogenous mix Solvent = major component of a solution Solutes = minor components of a solution If a solution will form then at least 2 substances have to mix uniformly Ionic & molecular solids do not change in comp when they dissolve in liquid solvents Entropy = disorder Like dissolves like Polar solvents will tend to dissolve polar solutes Nonpolar solvents will tend to dissolve nonpolar solutes For a given amount of solvent there’s a limit to the amount of solute that will dissolve at a given temp We call a solution that contains the ma amount of solute = saturated Solution that contains less than the max amount of solute = unsaturated Supersaturated = possible to form a solution that contains more solute than is present in the saturated case In saturated solution there is a solid phase and solvated phase of the solute Solid phase dissolves at the same rate as the solvated phase crystallizes If something upsets the equilibrium & causes crystallization to take place more rapidly than solvation more crustal solid will form Precipitate = when this takes place super rapidly this solid will form Solubility of all solids in water is aﬀected by temp General Procedure: Recover salicylic acid Recover copper sulfate Remove water of hydration Would expect the solubility of most solids to increase as the temperature of the solvent increases…at elevated temperature, there is more kinetic energy available to break the intermolecular forcers and dissolve the solute In preparation for a separation by ﬁltration, we add a solvent to extract one component of a mixture, leaving the others as solids. Which one of the following is an acceptable term for the liquid portion…Supernatant Filtration is useful for separating a solid from a liquid We warm the mixture after adding hate rot it to increase the rate at which the entire mixture dissolves Fractional Distillation…a separation technique that takes advantage of boiling point diﬀerences We add ethanol to our solution to lower the solubility of copper(ll) sulfate pentahydrate You will separate the “known” components of a binary mixture… Salicylic acid, water, Copper(II) sulfate pentahydrate The solubility of a gas decreases as we increase a solvent’s temperature because at elevated temperature, the kinetic energy of the gas molecules increase, making it easier for them to escape the liquid phase ***complicated calculations pay attention to calculations*** Exp 14: Graphical Analysis Overall Purpose: ﬁnding relationships btw variables through eqs & graphs, relates to Avogadro’s law which gives us a relationship btw the volume (V) of an ideal gas as a function of moles (n) General Procedure: y = mx + b y - dependent variable (on y-axis) x - independent variable (on x-axis) m - slope b - y-intercept direct relationship: y = kx^n indirect relationship: y = k/x^n
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