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Introduction

Renee Buettel Period D4 Ms. Parziale 1/7/08 Lab #10: Mole Ratios in a Chemical Reaction Paul Bergin Abstract The main objective of this lab experiment was to balance the given chemical equation and to find the correct mole-to-mole ratio of it. The theoretical balanced equation was Pb(NO3)2(aq) + K2Cr2O7(aq) --> PbCr2O7(s) + 2KNO3(aq). In addition, the ratio of moles was one to one.and the correct mole-to-mole ration was one to one. The experimental results matched this ratio. The theory that was proven was that balancing equations give the correct mole ratio of a chemical equation. Introduction In a chemical equation, there are two sides. The chemicals on the tail end are called the reactants and the chemicals on the other side are called products. An example of this given by Coefficients (2008) is 2H2 + O2 --> 2H2O. In this example, "2H2 + 02" is the reactants and "2H2O" is the product. Also, "-->" is the sign for "yield." The big 2s in front of H2 and H2O are called coefficients. In this case, the first 2 indicates that there are 2 molecules of H2, which also means that there are 4 atoms of hydrogen in the reactant part of the equation. The other 2 signifies that there are 2 molecules of H2O as the product. ...read more.

Middle

with K2Cr2O7 to form PbCr2O7(s) + KNO3(aq). Another objective of the lab is to learn how to balance equations. The correct mole ratio of the compounds is one to one because when the equation is correctly balanced out, it is Pb(NO3)2(aq) + K2Cr2O7(aq) --> PbCr2O7(s) + 2KNO3(aq). The well ratio of reactants that should result in the most product will be well 5 because the balanced equation has the ratio one to one, and well 5 has 5 drops of lead nitrate and 5 drops of potassium dichromate, which simplifies to 1 to 1. Methods 1) Obtain about 10 mL of K2Cr2O7(aq),and about 10mL of Pb(NO3)2(aq). (These amounts do not have to be exact, but should be close so as not to waste any of these solutions later.) 2) Using micropipettes as droppers, mix the two reagents by mixing drops according to the table #1 below. Mix the two reactants in the wells of the microchemistry plates. Be certain to use the line of wells near the edge of the plate such that you can see the results easily. NOTE - the wells are numbered on the plate and should correspond to the data table 3) For each well, mix WELL with the microspatula after adding the reagents. (Remember to clean off spatula after each stirring so as not to mix extra reactants not accounted for by well#) ...read more.

Conclusion

Although the hypothesis was correct, there could have been a few possible sources of error. One error source could have been that the compounds were not completely dissolved in water. This would cause the reactions to not happen as strongly, resulting in wrong results. Another possibility is that the droppers could have been contaminated, which would also result in wrong results. Also, if the two compounds weren't mixed with a toothpick, the compounds wouldn't combine enough. In addition to the main objective being met, the other objective, which was to balance equations, was also met. There is evidence of this in the hypothesis, where the chemical equation used in the lab is correctly balanced. The hypothesis turned out to be correct, and both objectives were met. In conclusion, this was a successful lab. Resources 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 McGraw-Hill. (n.d.). Chemical Reactions: Reactions in Aqueous Solution - Precipitaion Reactions Retrieved January 29th, 2008, from http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/cr/m3/s2/ Zahm (2008). Mole & Mole Ratios Retrieved January 29th, 2008, from http://dbooth.net/mhs/chem/moles.html Aqueous solution. (10/2005). Retrieved January 29th, 2008, from http://www.biology-online.org/dictionary/Aqueous_solution Stochiometry limiting reactant. (n.d.). Retrieved January 29th, 2008, from http://www.chem.tamu.edu/class/majors/tutorialnotefiles/limiting.htm The Six Types of Chemical Reactions. (n.d.). Retrieved January 29th, 2008, from http://misterguch.brinkster.net/6typesofchemicalrxn.html ...read more.

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