Limiting Reactant Lab

The Relationship between Reactants and Products
Introduction
In a chemical reaction, the amount of starting material for a chemical reaction limits the amount of product that can be formed.1 The principle of limiting reactants relates to this lab because the limiting reactant is the substance that is used up first in a chemical reaction. The amount of product was limited by that reagent. The excess reactants were considered to be the other reagents that were presented in excess of the quantity that was reacted with the limiting reagent. The theoretical yield was determined as the amount of product obtained when the limiting reagent was completely used. The limiting reagent was identified in order to calculate the percent yield of the reaction.
The purpose of this experiment was to determine how the amounts of reactants affect the amount of product made. Specifically, it was about to determine the relationship between calcium chloride and sodium iodate in a chemical reaction that produced calcium iodate and sodium chloride.
Methods
After choosing to use sodium iodate for the equation, five Erlenmeyer flasks were labeled 1-5.
25 mL of sodium iodate solution was added to each flask. Using 10 mL and 25 mL graduated cylinders, the following volumes of CaCl2 solution with a concentration of 22 g/L was added to the Erlenmeyer flasks. In flask 1, 5 mL of CaCl2 solution was added. In flask 2, 15 mL of CaCl2 solution was added. In flask 3, 25 mL of CaCl2 solution was added. In flask 4, 35mL of CaCl2 solution was added. In flask 5, 40mL of CaCl2 was added. The mixture was stirred into each flask. The observations about the reaction in each flask was recorded in the Results and Analysis section. The filtration process was the same for each product. First, the suction filtration apparatus was set up. Using a Buchner funnel, the funnel was fit in a filter flask, which is an Erlenmeyer flask with a second opening off the side of its neck. The second opening was attached to an aspirator, which provided the vacuum. A circular piece of filter paper was placed over the holes in the bottom of the Buchner funnel. A heavy rubber tube was connected to the side arm opening on the filter flask. Then, the tube was attached to a special side opening on a water
faucet.
The filter funnel was cleaned and rinsed with a small amount of 0.1 M HCl and distilled water.
A piece of filter paper was placed on the funnel and moistened with distilled water. With the aspirator on, the contents of flask 1 was poured into the funnel. The flask was rinsed out with distilled water and poured into the funnel in order to get most of the salts out of the funnel. The aspirator sucked the filtrate through the filter funnel. Once most of the liquid has been removed from the filter funnel, but the solid was still wet, 10 Ml of ethanol was added to the solid in the filter funnel. The ethanol was sucked through the filter funnel. The aspirator continuously ran in order to dry the solid on the filter funnel. Five vials were obtained and labeled with name, reaction number, and the flask number. The empty vials were weighed and their mass was recorded. When the solid was dry enough to remove from the filter funnel, the aspirator was turned off and the filter paper was removed from the suction flask. A spatula was used to gently remove the solid from the filter paper and placed into the corresponding vial. This process was repeated for all five Erlenmeyer flasks. Once completed, the vials with the solid contents were massed. After a week of drying, the vials were obtained and massed again. A graph using Excel was
prepared.
Results
This lab focused on providing evidence to the varying amounts of one reaction while the other reactant remained constant. The purpose of this experiment was to determine how the amounts of reactants affect the amount of product made. It was determined that the increase in calcium chloride resulted in an increase in the mass of the precipitate. However, a plateau formed in the calcium iodate when the amount of calcium chloride added to the sodium iodate increased. This was observed in Graph 4.1, the change between Erlenmeyer flask number two which contained 0.33g of calcium chloride and produced 0.474g of calcium iodate and Erlenmeyer Flask number four which contained 0.77g of calcium chloride and produced 0.477g of calcium iodate. This data showed that the amounts of reactants was directly inferred with the results in the products. The limiting reactant was sodium iodate. The graph correlated with this claim because the mass of the CaCl2 leveled out due to the limiting reactant not allowing any more product to be made. This data was analyzed the way it was in order to determine the relationship between the mass of the reactant and the mass of the product.
The mole is useful in chemical reactions because it gives a way to determine the ratio of the number of atoms in an element to its weight. A mol was calculated as the number of atoms or molecules that make up a certain weight.2 Since the number of atoms or molecules could not be counted directly, the mol gave a way to calculate the weight of the elements being mixed into a compound in order for them to reach stoichiometric equilibrium.
Some experimental errors that occurred in this experiment were that not all the salt from the flask was transferred to the funnel when transferring it from the flask to the aspirator. This can be fixed by using a different device to mix the calcium chloride and sodium iodate. Another experimental error was the salt content in the filter stuck to the filter paper and does not transfer completely to the vials. This can be fixed by adding a larger amount of ethanol to the filter in order to crystalize the salt more. Lastly, the filter does not catch all the salt. The filter was supposed to drain just the sodium chloride. However, some of the calcium iodate went under the filter paper and was not removed therefore, the mass of the salt content was lower due to the fact some salt was lost during the filtration process. By using a different filter paper or a different funnel, the salt cannot fit though the filter paper or holes in the filter allowing for a more accurate measurement on the amount of calcium iodate content.