CHEM 152 Purpose and Methods for all Labs
CHEM 152 Purpose and Methods for all Labs CHEM 152
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This 4 page Class Notes was uploaded by Angel Lee on Tuesday June 9, 2015. The Class Notes belongs to CHEM 152 at University of Washington taught by Kevin O'Malley in Spring 2015. Since its upload, it has received 305 views. For similar materials see General Chemistry in Chemistry at University of Washington.
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Date Created: 06/09/15
CHEM 152 Labs Purpose and Methods Experiment 1 Weak Acid Titration Purpose The purpose of this experiment is to determine the concentration of the weak acetic acid by performing titrations using the strong base sodium hydroxide After the concentration of sodium hydroxide is known it will be used to titrate an unknown solution of acetic acid until the acid base indicator phenophthaein changes the solution coor into a faint pink Method A 01 M solution of sodium hydroxide and 01M solution of acetic acid will be provided in this lab In the rst part of this experiment potassium hydrogen phthaate KHP will be used to standardize the sodium hydroxide NaOH so that the concentration of sodium hydroxide can be calculated Assuming that KHP and NaOH will react in equal amounts at the titration endpoint we can assume that the following calculation is valid moles of KHP moles of NaOH and solve for the concentration of NaOH using the equation In the second part of the experiment the concentration of acetic acid will be calculated in a similar way Once the solution in the second part of the experiment reaches the end point the volume of NaOH that was titrated wi multiplied by the calculated concentration of NaOH to determine the number of moles of NaOH Assuming a stoichiometry of 1 to 1 for NaOH and acetic acid we can use the mole of NaOH to solve for the concentration of acetic acid using the following equation Experiment 2 Buffers Purpose The purpose of this experiment is to determine and compare the buffering capacities of various acetate solutions and solutions prepared with aspirin and buffered aspirin Method 05 M sodium hydroxide 05 M hydrochloric acid sodium acetate trihydrate aspirin buffered aspirin and 01 M acetic acid will be provided in this lab In the rst part of the experiment the appropriate amount of mass of aspirin and buffered aspirin will be measure to prepare two sets of solutions On the other hand sodium acetate trihydrate will be measured to prepare a stock solution that will be prepared with acetic acid Thereafter the initial pH values of each solution prepared with acetic acid and sodium acetate trihydrate will be measured using a calibrated electrode After the addition of HCI the nal pH values of each solution will be recorded In the same manner the initial and nal pH values of the remaining solutions with the addition of NaOH will be recorded In the nal part of the experiment the same procedures from the previous part will be repeated however using the solutions prepared with aspirin and buffered aspirin Using the record values from each experiment the buffering capacity of each solution will be calculated using the equation Buffer capacity mmoles of HCI NaOH added Change in pH Experiment 3 Thermodynamics Calorimetry Purpose The main purpose of this experiment is to determine the heat capacity of a calorimeter in order to measure the enthalpy of fusion of ice the enthalpy of neutralization of two exothermic reactions and the enthalpy of hydration of magnesium sulfate Methods For the rst part of the experiment a calorimeter water and a digital power supply will be provided To determine the heat capacity of the calorimeter the calorimeter will be lled with 80 mL of water As a known amount of heat is applied by the digital power supply to the calorimeter the change in temperature will be recorded The following equation will be used to calculate the heat capacity C ca q ca Once the heat capacity of the calorimeter is determined it can be used to measure the enthalpy of melting an ice cube Knowing that the heat lost by the calorimeter must be equal the heat gained by the ice water the following equation can be used to determine the enthalpy C cal m ice where delta Tcal In the third part of this experiment 05 M HCI 05 M NaOH and 05 M HCH3COO will be provided in the lab The rst neutralization reaction will be involve HCI and NaOH and the second will include HCH3COO and NaOH both of which are exothermic reactions Knowing that the heat gained by the calorimeter is equal to the heat lost by the exothermic reactions we can again use q Ccal to calculate the enthalpy of the neutralization reactions In the nal part of the experiment the enthalpy of hydration of MgSO4 will be determined by measuring the enthalpies of two related reactions The enthalpies of these reactions will be used with Hess39s Law to calculated the enthalpy of hydration ofMgSO4 Experiment 4 Thermodynamics Temperature Dependence of Solubility Purpose The purpose of this experiment is to generate a calibration curve for stock solutions of varying molarities of KCI and KHP and to determine the concentration of HPquot in two types of KHP solutions The calibration curve will be generated with the measurements attained from a ame photometer On the other hand the HP concentrations of solutions with varying temperatures and with or without KCI will be determined through titrations with NaOH in order to calculate the solubility product for KHP Ksp After the Ksp of both types of titrations is determined they will be compared to verify that the Ksp for KHP is a constant Method In Part I of the experiment 0005 M KCI 05 M KCI KHP saturated solution and a ame photometer will be provided The KCI and KCI KHP saturated solutions will be used to create stock solutions of varying molarities which will be kept in test tubes Afterwards the solutions will be used to calibrate the ame photometer which will be used to measure the intensity of the emission of the KCI solutions These measurements will then be plotted with the Kquot concentration of each solution generating a calibration curve represented by the following equation Ln Ksp In Part II of the experiment soid KHP 01 M NaOH 0005 M KCI and six prepared KHP solutions at various temperatures will be provided for the purposes of standardizing NaOH and performing titrations Along with the six prepared KHP solutions at various temperatures a seventh KHP solution at room temperature with the addition of KCI will be titrated in order to determine the HPquot concentration of each solution Once the HPquot concentrations of each solution is recorded this data can be used to calculate Ksp which can be calculated for a saturated solution by the equa on Ksp Or for a solution containing KHP and KCI with the equation Ksp gtlt Lab 5 Purpose The purpose of this experiment is to prepare batteries using halfcell redox reactions and to monitor the change in voltage as a result of changes in half cell concentrations by determining the standard reduction potentials of the four half cell reactions Method 1M CuNO32 1M AgNO3 1M ZnNO32 1M PbNO32 and 01 M CuNO32 will be provided in the lab along with wires made of silver zinc lead and copper The wires will be used to create electrodes which will be immersed into metal ion solutions whose haf ce potentials will be measured using a Fluke multimeter Once con dent measurements are attained voltages of batteries consisting of two already prepared haf cells will be measured In the nal part of the experiment data from the rst part of the experiment will be used with the Nernst equation to compose a battery with a cell potential of 05 V by diluting the metal ion solution accordingly Lab 6 Purpose The purpose of the rst part of this experiment is to determine the value for the Rydberg constant by measuring the wavelengths of hydrogen and helium emission using a spectroscope and spectrophotometer The purpose of the second part of this experiment is to identify the cations in unknown solutions by conducting ame tests Method In part 1 of the experiment a hydrogen discharge lamp with a spectroscope and a helium discharge lamp with a spectroscope will be provided in the lab The spectroscope will be used to identify the wavelength of the color while the intensity will be determined qualitatively through observations Afterwards the spectrophotometer which will output a series of peaks on the screen at the wavelength corresponding to the emission lines will be used to measure the hydrogen emission spectrum Using this data the Rydberg constant will be determined using the equation In part 2 of the experiment 05 M of CuCl2 05 M of BaCl2 and several unknown solutions will be provided in the lab The emissions of the known and unknown metal atoms will be observed using ame tests Using the understanding that light emitted by an atom is characteristics of that atom no matter what other elements are combined with it and no matter what its origin the unknown metal atoms will be determined
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