Stoichiometry Lab Report

In order to begin this experiment, first one must find the balanced chemical equation for the reaction which occurs between the aluminum and copper (II) chloride. This balanced equation being 2Al(s)+3CuCl2 (aq)3Cu(s)+2AlCl3 (aq). After finding this equation, one must use the process of stoichiometry in order to find how many grams of aluminum are needed in order to produce 0.15 grams of copper. In this experiment, the purpose was to produce between 0.1 and 0.2 grams of copper, so one should attempt to produce 0.15 grams of copper seeing as it is the average of those two numbers. The first step in the stoichiometric process which one has to complete is finding how many grams of copper are in one mole of copper.

The lab started off by measuring critical materials for the lab: the mass of an an empty 100 mL beaker, mass of beaker and copper chloride together(52.30 g), and the mass of three iron nails(2.73 g). The goal of this experiment is to determine the number of moles of copper and iron that would be produced in the reaction of iron and copper(II) chloride, the ratio of moles of iron to moles of copper, and the percent yield of copper produced. 2.00 grams of copper(II) chloride was added in the beaker to mix with 15 mL of distilled water. Then, three dry nails are placed in the copper(II) chloride solution for approximately 25 minutes. The three nails have to be scraped clean by sandpaper to make the surface of the nail shiny; if the nails are not clean, then some unknown substances might accidentally mix into the reaction and cause variations of the result.

Secondly, the test tubes were not cleaned out. If there was residue from other chemicals on the test tube there could be an error in the reaction. Cleaning out the test tube before starting lab could prevent this. Finally, residue on gloves could have got into the solution. This could have caused an error in the reaction.

The question is, how does a physical or chemical change affect the mass of a substance within a closed system? To respond to this question, my group did a lab to determine whether or not the mass would change or not. Our lab was to have a plastic bag containing baking soda, then add a cup of vinegar and a block of clay to the mix. We made sure to weight every element separately and then add them up for our total mass of 31 grams before the reaction. During the reaction, as soon as the vinegar was poured in there was a gas produced, bubbles.

Materials The amount of copper that was obtained was not the same as the mass expected, as it was significantly greater. This may be caused by side reactions, or if the elements that were used were not truly pure. These may be some reasons that caused the amount of copper to be greater, as the mass calculated should generally be close to, or less than the mass expected in pure reactions.

The precipitate left on the beaker would not be accounted for in the calculations, and would result in a lower measured mass and

A third error was miscalculating the volume in each vial, which could have been prevented by making sure the beads accurately made up for any difference in volume between the

One big error was the inaccurate information. The error mainly had to deal with the type of rocks used in the experiment. The lava rocks did help but easily fractured into sediments. So it was difficult to gather accurate weight after the trial was done because all of the small sediments couldn’t be gathered and weighed. If this experiment is to be done again in the future, it would be best to change the type of rock that is used in the experiment.

Firstly, because the NaHCO3 compound was not stored in a sealed container, therefore dust particles could have changed the results, and making the product impure. Also, there are uncertainties associated with the instruments used in this experiment. This, if the products were measured slightly more than should be, this could have affected the concentrations of the solutions, and therefore causing a larger

A final source of error that was made during the experiment is the concentration of the products used were low so there might have been other thing in the vinegar to add mass to the final solution. A solution to this error could have been to use a more concentrated acetic acid because the vinegar could have other products that could ruin your calculations in the end if it did not dissolve with the

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

The lab manual states that for the titration of NaOH and HCl, a volume of 7mL of titrant should complete the reaction, however, the average for the experiment was only 6.25mL. This smaller amount of NaOH could have occurred by adding too much phenolphthalein, which would have caused the substance to turn pink sooner, rather than when the reaction was complete since phenolphthalein is a weak acid. Another example of error occurred in the titration of NaOH and H2SO4, a substantial difference appeared in the theoretical ratio of 2:1 and the experimental ratio of 2.5:1. This could have occurred by adding past the titration end point, resulting in more NaOH than necessary, thus altering the ratio. Both reactions involving Ba(OH)2, had relatively low percent errors, especially in the HCl reaction (approximately 5%) and a higher percent error with H2SO4 (approximately 20%).

50. atomic radius, trends in the periodic table As you go across the periodic table, the atomic radius decreases because the number of protons increases along with the number of electrons but the shielding does not change so they are more attracted to each other and the electrons are pulled more inward which makes the atomic radius smaller as you move across the periodic table. 51. Rutherford’s experiments, gold foil, alpha particles

Properties of Ionic and Covalent Substances Lab Report Introduction The purpose of this lab was to determine which of the following substances: wax, sugar, and salt, are an ionic compound and which are a covalent compound. In order to accurately digest the experiments results, research of definitions of each relating led to the following information: ionic compounds are positive and negatively charged ions that experience attraction to each other and pull together in a cluster of ionic bonds; they are the strongest compound, are separated in high temperatures, and can be separated by polar water molecules. A covalent compound forms when two or more nonmetal atoms share valence electrons; covalent compounds are also

Introduction to Stoichiometry What does stoichiometry mean? Before trying to understand what stoichiometry means, you first need to know what chemistry deals with. Chemistry is a branch of science that deals with matter and all the change in composition it undergoes.