EXP 14 Baking Soda & Stoichiometry Name: _______________________________ Student ID: ___________________________ Chem 50 — De Anza College The goal is to find the percent yield from the decomposition reaction of sodium hydrogen carbonate (NaHCO3). Then to determine the percent of sodium hydrogen carbonate in an unknown mixture, using stoichiometry and dimensional analysis. Review the discussion and example calculations for this experiment on page 157-159 of your lab manual. ! 2 NaHCO3 (s) → Na2CO3 (s) + H2O (g) + CO2 (g) eqn #1: balanced equation for decomposition of sodium hydrogen carbonate Part A of this lab involves testing the process, to see if we can experimentally determine the amount of NaHCO3 in the test tube. We compare our results to theory to see how well the experiment performs and report that comparison as percent yield. Part B of this lab involves heating our unknown mixture and using the observed difference in mass and our understanding of stoichiometry to determine how much NaHCO3 was in the original mixture. We report this as the percent NaHCO3 in the unknown substance. We were not able to conduct this experiment. Instead of collecting your own data for this lab, you are being provided with the attached data. This data will serve as your “data” section for your experiment report. Copyright ChemLectures™ 1992-2015 Exp # 14 Name: ________________________________ Student ID: ____________________________ Chemistry 50 Prep Chemistry De Anza College Experiment Title: Baking Soda (Stoichiometry) Unk#: ____ Bench / Locker : _____/_____ (write N/A if no unknown for this experiment) This square for use by instructor. _______ quiz A _______ quiz B _______ report _______ total Unknown Composition or Identity: A report must be submitted receive credit for your participation in all lab experiments. You may only report on experiments in which you fully participated. Reminder: Experiment reports generally include the following sections. section should start with a new page and be clearly labeled. Each ➡ COVER PAGE (this page) ➡ PRE-LAB ➡ Provide clearly expressed answers to the questions on pages 161-162 from your lab manual. ➡ DATA ➡ Data has been provided for this experiment. Use the filled out data table provided as your data for this experiment. ➡ CALCULATIONS ➡ Provide your calculations for determining the percent yield of sodium carbonate in Part A. A calculation guide is included. ➡ This demonstrates that we can rely on the amount of amount determined by experiment, when we use this same process in part B. ➡ Provide your calculations from Part B for determining the percent sodium hydrogen carbonate in the unknown. A calculation guide is included. ➡ CONCLUSIONS ➡ Give your average percent yield from part A. ➡ Give your determined percent NaHCO3 from your unknown. ➡ QUESTIONS ➡ Clearly present answers to questions from pages 165-166 from your lab manual. ta >t EXPERIMENT 14 NAME DATE SECTION PRELABORATORY ASSIGNMENI* 1. Providethe key tenn that conespondsto eachof the following definitions. (a) therelationship of quantities(i.e.,massof substance or voiumeof sas)in a chemicalreactionaccordingto thebalancedchemicalequation (b) themassof 1 moleof anysubstance expressed in grams (c.) a procedurefor obtainingthe massof a sampleby frst welghinga container andthenweighingthecontainerwith the sample (d) a thevoiumeof a gasby measuring thevolume oI^technique-for-determining wafer 1t dlsDlaces (e) the amountof productexperimentallyobtainedfrom a reaction (f) the amountof productthat is calculatedfrom a given amountof reactant (g) the actualyield comparedto the theoreticalyield expressedasa percent Key Terms: actualyield,_molarmass(l\4M),percentyield, stoichiometry,theoreticaiyield, volumeby displacement, weighingby difference 2. How do you tell whenthebakingsodasampleis decomposed completely? 3. Is it possibleto obtaina percentyield of Na2CO3thatis greaterthan1002o? 4. Whataremajorsources of experimental error? * Answersin Appendix J Copyright O 2013Pearson Education Decomposing Baking Soda 161 Referto with heatto produce0.991^g-Na2C^O3. .5. A 1.555-9salnpleof bakingsodadecomposes yield Na2co3. of theoretical the for 14.1andshowthecalculation Example-Exercise What is the percentyield of sodiumcmbonate,NazCO:? of 0.325'g.Refer sodais heatedandhasa nrass-loss 6. - A 1.473-sunknownmxture with baki4g in themixture. percentage NaHCO3 the io iiua1o't" B""r"lse 14.2andshowthdlalculation for 7. What safetyprecautionsmustbe observedin this experiment? 14 L62 Experiment [email protected] DATA Part A: Percent Yield of Na2CO3 Trial #1 Trial #2 mass Test Tube 10.860 g 10.753 g mass Test Tube + NaHCO3 (before heating) 12.894 g 12.648 g mass Test Tube + Na2CO3 (after heating) 12.116 g 11.924 g Part B: Percent NaHCO3 in Unknown Trial #1 Trial #2 “B” “B” mass Test Tube 10.653 g 10.782 g mass Test Tube + Unk Mixture (before heating) 12.342 g 12.607 g mass Test Tube + residue (after heating) 11.874 g 12.102 g Unknown ID Copyright ChemLectures™ 1992-2015 CALCULATIONS Part A: Percent Yield of Na2CO3 Calculate by difference the mass of your starting NaHCO3. Calculate by difference the mass of Na2CO3 produced (experimental or actual yield) This is the only matter left in the test tube. Determine the theoretical yield (mass of Na2CO3 theory says would have been produced). Determine the percent yield (ratio of theory to actual yield) of Na2CO3. And average percent yield of the two trials. Trial #1 Mass of starting NaHCO3 Experimental Yield Na2CO3 Theoretical Yield Na2CO3 Percent Yield Na2CO3 Copyright ChemLectures™ 1992-2015 Trial #2 Average CALCULATIONS Part B: Percent of NaHCO3 in Unknown Mixture Calculate by difference the mass of your starting mixture. Calculate by difference the mass of H2CO3 (H2O + CO2) produced. This is how much matter was lost from our starting material after we heated it. Using the H2CO3 produced, calculate how much NaHCO3 must have been in the original sample. Determine the percent of NaHCO3 in the original sample. Report an average percent for the two trials. Trial #1 Mass of starting mixture. Mass of H2CO3 (H2O + CO2) produced. Theoretical Starting Amount of NaHCO3 Percent of NaHCO3 in starting mixture. Copyright ChemLectures™ 1992-2015 Trial #2 Average NAME SECTION L. A I .225-9sampleof purelithium hydrogencarbonaleis decomposed by heatingto produce 0.660g lithium carbonate.Calculatethe theoreticalyield andpercentyield of Li2CO3. 2LiHCO3(s) ; LizCO:(s) + HzO(g) + COz(g) A 1.205-9samplemixture of lithium hydrogencarbonateis decomposed by heating.If the masslossis 0.275g, what is the percentageof LiHCO3in the unknownmixtwe? 2LiHCO3(s) ; LizCO:(s) + HzCOa(g) [email protected] BakingSoda Decomposing L6s with heatto give lithium chlorideandoxygengas.If-l^.115 g of -3. Liihium ctilorateis decomposed how manymltliten of oxygengasis releasedat STP? tidrium ctrtorateis decompbsed, 2LiClOg(s) 1 2lic1(s) + 3oz(g) 4. Lithium metalreactswith waterto give lithium hydroxideandhydrogengas.If-75.5mL of hydrogengasis producedat STP,whatis themassof lithiummetalthatreactedl 2 Li(s) + 2 HzO(l) -J 2 LiOH(aq) + HzG) 5. (optional)The Solvayprocessis usedto manufacturebakingsoda NaHCO3,Inthe process, bbz, lri:, rtzo, andNaCl reactto producebaking soda.If 25.0L CO2and20.0 L NH3 react at STp, with excesswaterandsodiumclrloride,what is the limiting r€actant?Calculatethernass of baking sodaproduced. [email protected])+ NHIG) + H2O(1) + NaCl(s) -+ ulluung KeacElnt NaHCOg(s)+ NILCl(aq) MassNaHCO: { I t4 166 Experiment [email protected]€PearsonEducation '( (

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