Lab Report: Stoichiometry Lab Oct. 27, 2011 Claire Elizabeth Lab Partners: Hannah Signature:___________________ Introduction- Baking soda and vinegar are two common materials found in almost every household. That, plus the fact that all the starting and finishing materials are non hazardous and safe, is why this is one of the first chemical reactions that many people are exposed to The purpose of this experiment tests which of the two reactants (vinegar and baking soda) is the limited reactants. It is hypothesized that the limited reactant of this experiment is the baking soda.
Materials- * 2 beakers * Sodium bicarbonate * Vinegar * Beral Pipette Procedure- 1) Label the beakers A and B. 2) Weigh the beakers to two decimal places. 3) In Beaker A, place approximately . 5- . 75 g of baking soda. 4) Weigh Beaker A with the powder to two decimal places. 5) Fill Beaker B one third to one half full of vinegar. 6) Place the pipette into Beaker B. 7) Weigh Beaker B with the vinegar and pipette to 2 decimal places. 8) Slowly transfer the liquid from Beaker B to Beaker A using the pipette until all of the powder is dissolved. ) Take a final weight measurement of Beaker A after the reaction, measuring to two decimal places. 10) Take the weight measurement of Beaker B with the pipette after the reaction, measuring to two decimal places. 11) After the experiment is over, there should be six measurements in all (all to two decimal places. ). a. Original mass of Beaker A b. Mass of Beaker A with powder. c. Mass of Beaker A after reaction d. Original mass of Beaker B e. Mass of Beaker B with liquid f. Mass of Beaker B after reaction 12) The beakers should now be washed out and dried with a paper towel. 3) The procedure should be repeated a second time for a second trial to account for accuracy, including all six measurements. Analysis Part 1- Six Original Measurements- For the reaction: Mg + 2HCl MgCl2 + H2 2) Balanced Equation- Na HCO3 + H(CH3COO) > NaCH3COO + H2O + CO2 3) 4) 5) 6) 7) 8) Analysis Part 2- The point recorded for this group is 0. 72 g of powder used and 0. 635 g of gas lost. This point is not on the line. Measurement error could be a reason why it appears that liquid was lost. The error for this graph is large.
Some possible causes of this error could have been human or machine error (machine meaning calculator) or carelessness in data. Analysis Part 3- 1) 2) The amount of sodium acetate produced cannot be determined. The products of the reaction that were weighed include sodium acetate and water, so there is no differentiation between the water and the sodium acetate. 3) 4) The limiting reactant for this equation would be NaHCO3 because there is a need for more than there actually is, causing the reaction to stop. Conclusions-
The purpose of this experiment was to react sodium bicarbonate with acetic acid, and from that, find the limiting reactant. It was hypothesized that sodium bicarbonate (baking soda) would be the limiting reactant, and through this experiment, the hypothesis was proved correct. Though care was taken to ensure an errorless environment, there were several errors. When beakers were set down on the scale, the weight would fluctuate by varying degrees, putting the partner’s measurements slightly off from the measurements of another’s. Human error of carelessness must also be accounted for.