Written documentation of scientific work is one of the most important methods for scientists to communicate their results. A written report documents the experimental findings with enough detail to duplicate the original results. Scientific reports are written in a standard format that includes an introduction, a description of the methods and materials used, a summary of the results, and a discussion of these results. Scientific papers published in journals also include an abstract and a bibliography. The ability to write a laboratory report in standard scientific format is a valuable communication skill because it provides access to the vast body of original scientific research. The laboratory reports in the general chemistry laboratory serve as an introduction to this process.
A written laboratory report is required for each experiment in the general chemistry laboratory course. Laboratory reports should be typed and in the format listed below. (See Turning Lead Into Gold for a sample report.)
Title of ExperimentIntroduction
This section should contain a brief summary of the background information and theoretical concepts needed to complete the experiment. It should also describe the purpose of the experiment.
Titration is a common procedure to determine the concentration of a solution. It is performed by adding a standard solution, which has a known concentration, to an unknown solution. The solutions undergo a chemical reaction. When there is an equal molar amount of both solutions, an indicator dye is used to signal the equal molar amounts of the solutions. From the chemical reaction and its stoichiometry, the concentration of the unknown solution can be calculated. An acid-base titration was used to find the concentration of a basic solution and then to determine the molecular weight of an unknown acid.
This section describes an individual's experiment. It should be written as a narrative of the work completed in the lab and NOT a reproduction of the procedures listed in the lab handout. Copying these procedures is plagiarism. Instead, the procedures should detail each individual's unique assignment in the laboratory.
Four FTIR spectra sample cards and four pieces of plastic material samples, an overhead projector slide, a plastic bag, saran wrap, and unknown sample "A" were obtained. Each piece of the sample materials was cut to a size just larger than that of the hole in the spectra sample card. The cut pieces of samples were stretched smooth and placed over the hole on their own respectively labeled FTIR sample card. The material samples were held fastened to the sample card with clear adhesive. An FTIR card with no material sample attached to it was used to blank the spectrometer. The blank card was then removed and replaced with the first sample card. The first sample was then scanned, and the amount of light absorbed was recorded by the instrument. This procedure was repeated for the remaining two known materials and for the unknown material.
This section includes the data and calculations in table or graph form. Calculations can be hand written if necessary. Graphs or tables on separate pages should be included in this section.
Unknown Water Soluble Iodine Vinegar Alkaline 1 Yes --- No bubbles Non-alkaline 2 No None Bubbles --- 3 Yes --- No Bubbles Non-alkaline 4 No Yes No Bubbles Non-alkaline 5 Yes --- --- Non-alkaline
This section includes a few paragraphs including pertinent observations, equations or reactions, sources of error and a summary of the results. Pertinent observations are any observations that affect the outcome of your experiment, or mark a crucial step in your experiment. They could include color changes at the end of a titration experiment, formation of a precipitate, change of state, as in crystallization, or any major procedural changes, ie. you spilled an unknown amount of acid into your solution, back titrated to discover the amount added, and then calculated your new concentration. Any major concepts or equations used should also be included in this section. If you used the ideal gas law to determine the volume of your unknown gas, for example, you should state what the ideal gas law is and how the appropriate equation is used. Finally, include a discussion of any deviations from the expected results.
Ascorbic acid is present in varying amounts in both IGA brand Pink Grapefruit Juice Cocktail and Ocean Spray White Grapefruit Juice. By titrating a standard iodine solution into samples of these juices, the average amount of vitamin C in the juices was found to be 1.17 g per 8 oz. serving and 0.648 g per 8 oz. serving respectively. The results show that each of the two juices contain more than enough vitamin C per serving to met the RDA of 60 mg per day set by the Food and Nutrition Board. The amount, in grams, of ascorbic acid calculated from the titration data in each juice sample is a reasonable number and the discrepancy between the results found for each respective sample is small enough to be attributed to experimental error.
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