Stoichiometry And Limiting Reagents Lab Report

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Verna Wang
Hannah Palmer
CHEM 101-069 Lab
11-19-16
Stoichiometry and Limiting Reagents Lab Report
Purpose: We are using the reaction of sodium hydroxide and calcium chloride to illustrate stoichiometry by demonstrating proportions needed to cause a reaction to take place.
Background: Just like a recipe would call for a specific amount of one ingredient to a specific amount of another, stoichiometry is the same exact method for calculating moles in a chemical reaction. Sometimes, we may not have enough of or too much of one ingredient , which would be defined as limiting and excess reagent, respectively. Ideally, every mole of each reagent would be used up, and theoretical yield, we are assuming that every last mole of the reactants would
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(0.01 moles of NaOH) x (1 mole Ca(OH)2/ 2 moles of NaOH) = 0.005 moles of Ca(OH)2
Tube 1:
(0.0020 moles of CaCl2) x (1 mole Ca(OH)2/ 1 mole of CaCl2) = 0.002 moles of Ca(OH)2
(0.002 moles of Ca(OH)2) x (74.08 grams/mole) = 0.1 grams = theoretical yield
Tube 2:
(0.0035 moles of CaCl2) x (1 mole Ca(OH)2/ 1 mole of CaCl2) = 0.004 moles of Ca(OH)2
(0.004 moles of Ca(OH)2) x (74.08 grams/mole) = 0.3 grams= theoretical yield
Tube 3
(0.0050 moles of CaCl2) x (1 mole Ca(OH)2/ 1 mole of CaCl2) = 0.005 moles of Ca(OH)2
(0.005 moles of Ca(OH)2) x (74.08 grams/mole) = 0.4 grams =theoretical yield
Tube
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If only one reactant is increased, then the chemical reaction will only produce a certain amount of products after the limiting reagent is used up, and in this experiment, the most mass the reaction could produce was 0.4 grams. Although we kept adding calcium chloride, not adding sodium hydroxide in the same proportions will not yield more product, which is the main goal in conducting this lab. We should have seen a plateau at 0.4 grams to show that the limiting reagent inhibited further Ca(OH)2 production, but we made several mistakes in our experiment, which made the data unusable to conclude. Once again, the data is polluted, so these number are not accurate, but it is the data our group has to work with. The theoretical yield should have been more than the actual yield, and the percentages should have been less than 100. The actual data is the result on our experiment vs theoretical, which is based on the calculations above. I have also learned to pay more attention to draining out all of the product completely before continuing to test the experiment, as any small drop of contaminant can veer our results into a different

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