The limiting reactant is determined in this experiment

Experiment 8Prelaboratory AssignmentLimiting ReactantDate __________ Lab Sec. ______ Name ____________________________________________ Desk No. __________1. The limiting reactant is determined in this experiment.a. What are the reactants (and their molar masses) in the experiment?b. How is the limiting reactant determined in the experiment?2. Experimental Procedure, Part A.2. What is the procedure and purpose of “digesting the precipitate”?3. Two special steps in the Experimental Procedure are incorporated to reduce the loss of the calcium oxalate precipitate.Identify the steps in the procedure and the reason for each step.4. a. A sample of a CaCl2•2H2O/K2C2O4•H2O solid salt mixture is dissolved in ~150 mL of deionized water previouslyadjusted to a pH that is basic. The precipitate, after having been filtered, was air-dried and weighed. Data for Trial 1were obtained as shown. Complete the following table. (See Report Sheet.) Record calculated values with the correctnumber of significant figures.A. Precipitation of CaC2O4•H2O from the Calculation ZoneSalt Mixture3. Mass of salt mixture (g) ___________4. Mass of filter paper (g) ___________5. Mass of filter paper and CaC2O4•H2O (g) ___________6. Mass of air-dried CaC2O4•H2O (g) ___________B. Determination of Limiting Reactant1. Limiting reactant in salt mixture ___________2. Excess reactant in salt mixture ___________Data Analysis1. Moles of CaC2O4•H2O precipitated (mol)Show calculation. ___________2. Moles of limiting reactant in salt mixture (mol)See equation 8.1. ___________3. Mass of limiting reactant in salt mixture (g)Show calculation. ___________4. Mass of excess reactant in salt mixture (g)Equals mass of salt mixture minus mass of limiting reactant.Show calculation. ___________5. Percent limiting reactant in salt mixture (%)Show calculation. ___________6. Percent excess reactant in salt mixture (%) ___________4. b. For Trials 2 and 3, the percent CaCl2•2H2O in the mixture was 39.7% and 28.4% respectively.a. What is the average percent of CaCl2•2H2O in the sample? Data Analysis, B.b. What are the standard deviation and the relative standard deviation (%RSD) for the percent of CaCl2•2H2O inthe sample? Data Analysis, C and D.Laboratory Questions1. Part A.2. If the step for digesting the precipitate were omitted, will the reported “percent limiting reactant” in the saltmixture be too high, too low, or unaffected? Explain.2. Part A.3. A couple of drops of water were accidentally placed on the properly folded filter paper before its mass wasmeasured. However, in Part A.6, the CaC2O4•H2O precipitate and the filter paper were dry. As a result of this sloppytechnique, will the mass of the limiting reactant be reported too high, too low, or remain unaffected? Explain.3. Part A.5. Because of the porosity of the filter paper some of the CaC2O4•H2O precipitate passes through the filter paper.Will the reported percent of the limiting reactant in the original salt mixture be reported too high or too low? Explain.4. Part A.5. Excessive quantities of wash water are added to the CaC2O4•H2O precipitate. Will the mass of theCaC2O4•H2O be reported too high, too low, or remain unaffected? Explain.5. Part A.6. The CaC2O4•H2O precipitate is not completely air-dried when its mass is determined. Will the reported massof the limiting reactant in the original salt mixture be reported too high or too low? Explain.6. Part A.6, 7. The drying oven, although thought (and assumed) to be set at 125°C, had an inside temperature of 84°C.How will this error affect the reported percent by mass of the limiting reactant in the salt mixture . . . too high, too low,or unaffected? Explain.7. Part A.4 and Part B. In a hurry to complete the experiment, Anna withdrew two volumes of solution from Part A.2before the precipitate had settled. As a result, what dilemma might she have encountered in Part B? Explain.8. Part B.2. A reagent bottle on the shelf labeled 0.5 M NaCl was used in place of the 0.5 M CaCl2. Assuming C2O42– tobe in excess, what would be observed as a result of using this wrong reagent in this test? Explain.

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