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Determination of % Yeild

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Introduction

Renee Buettel Period D4 Ms. Parziale 1/31/08 Lab #11: Determination of % Yeild Paul Bergin Abstract The main objective of this experiment was to find the mole to mole ratio of is NaHCO3(s), or sodium bicarbonate, to NaCl, or sodium chloride when it is reacted with excess hydrochloric acid. The result of this was a 1 to 1 ratioThe other main objective, which was similar to the first, was to find the mole ratio of sodium carbonate to sodium chloride reacted with excess HCl. The result of this was a 1 to 2 ratio. The main theory proven in this lab experiment was the topic of percent yield. Introduction Stoichiometry is an important topic when dealing with chemistry. It is a very mathematical part of chemistry. It's used to calculate moles, percents, and masses of reactants and products in a chemical equation, according to Park (1996). A common stoichiometry problem gives an amount of a reactant and asks how much of the product will be formed. The same source explains that in a mass-to-mass problem, the first step is balancing the equation. Next, the mass is converted to moles using the molar mass of the given substance in the formula n=m/GFM. A mole ratio is then used to convert the moles of the known to the moles of the unknown. Finally, the moles are converted to mass using the formula n=m/GFM. ...read more.

Middle

Then using your dropper pipette, add the HCl drop by drop to the sodium bicarbonate in the evaporating dish. The reaction will be evident by the bubbling that takes place. Gently mix the reactants after every 3-4 drops of HCl. Continue adding HCl until the bubbling stops and all of the NaHCO3 is dissolved - this indicates that the reaction is complete. 4. Assemble the stand, ring clamp and wire gauze apparatus for heating as shown in the figure below. Cover the evaporating dish with the watch glass and place it on the wire gauze. 5. Gently heat the solution in the covered evaporating dish with a Bunsen burner flame in order to remove the water generated in the reaction (as well as any excess HCl present). The flame should be adjusted to a lower temperature and wafted under the evaporating dish constantly. Continue heating until the contents are completely dry. Note that the watch glass cover should also be dry! 6. After allowing the evaporating dish to cool to room temperature, measure and record the mass of the evaporating dish + watch glass + residue (NaCl). 7. Repeat steps 1 to 6 with a 0.3 - 0.4 g sample of sodium carbonate (Na2CO3). Results Calculations: Appendix A Table #1: Experimental and Theoretical Mass and Moles Produced from NaHCO3 Mass of NaHCO3 reactant Moles of NaHCO3 reactant Theoretical Moles of NaCl that should have been produced (ratio) ...read more.

Conclusion

Finally, the moles were converted to mass using the formula n=m/GFM. Percent yield was found by using the equation %yield=(actual mass of product/predicted mass of product) x 100. The hypothesis was correct. The mole ratio of each reactant to the product of NaCl in the first reaction was be to 1 to 1 due to the fact that the balanced equation was NaHCO3(s) + HCl(aq) --> CO2 + H2O(l) + NaCl(s). For the second reaction, the mole ratio of was be 1 to 2 because the balanced equation was Na2CO3(s) + 2HCl(aq) --> CO2 + H2O(l) + 2NaCl(s). All objectives were met. The main objectives, which were to find the mole ratios of sodium carbonate and sodium bicarbonate when reacted with excess hydrochloric acid, were accomplished. The percent yield equation was successfully used, which was a minor objective. Evidence of this is in Table #1. The second minor objective, which was to find the actual mass and moles of NaCl produced, was also met. There is also evidence of this in Table #1. In conclusion, this lab experiment was successful. Results Coefficients in Chemistry? (2008). Retrieved January 29th, 2008, from http://au.answers.yahoo.com/answers2/frontend.php/question?qid=20080116233108AAITP3g Chemistry Formulas (2005). Retrieved January 29th, 2008, from http://chemistryformulas.com/ How can I balance an equation? (n.d.). Retrieved January 29th, 2008, from http://misterguch.brinkster.net/eqnbalance.html J. L. Park (1996). ChemTeam: Stoichiometry: What is it?Retrieved February 9th, 2008, from http://misterguch.brinkster.net/eqnbalance.html Law Of Conservati0on of Mass Definition (n.d.). Retrieved February 9th, 2008, from http://chemistry.about.com/library/glossary/bldef5660.htm W. Volland (2005). Percent Yield for Chemical Equations. Retrieved February 9th, 2008, http://www.800mainstreet.com/6/0006-007-percent-yield.html ...read more.

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