Laboratory Techniques and Measurements
What color do you observe? When reacting phenolphthalein with an acid what color change do you expect? What color change do you expect with a base? Response: I observed a colorless mixture. When reacting phenolphthalein with an acid, the mixture will remain colourless but when reacting with a base the mixture would change fuschia. K. AgNO3 and NH3 (ammonia). Absorb this mixture onto a scrap of paper towel and expose it to intense light from a light bulb or the sun. Be patient and you will observe a change. Record your observation. Response: The mixture turned a greenish brown.
Questions A. Suppose a household product label says it contains sodium hydrogen carbonate (sodium bicarbonate). How would you test this material for the presence of sodium bicarbonate? Answer: Sodium Bicarbonate is a strong base. Therefore I would perform 3 tests. First test, I would verify if it would create a colourless bubble like liquid. For this test, I would add HCl to the household product. If the substance reacted with a colourless bubble-producing product, this test would be positive. In the second test, I would add Bromthymol to the household product, if it turns blue, this test would be positive.
Bromthymol turns blue when it comes into contact with a base. In the third test, I would add Phenolphthalein to the household product, if the product turns fuschia, this test would be positive. Penolphthalein turns fuschia when it comes in contact with a base. If all of the above tests are positive, this would indicate that there is sodium bicarbonate present. B. You know what color phenolphthalein and bromthymol blue turn when testing an acid or a base. Use the empty pipet in the Auxiliary Supplies Bag to test several (at least 3) household items including household cleaning products with bromthymol blue.
Rinse the pipet well before using it on the next household chemical. When finished with this experiment rinse the pipet well and return it to the Auxiliary Bag for use in future experiments. Name the items tested and record their results. What do these results mean? Answer: Items usedTest results powdered cleaning product with bleach Phenolphthalein – Fuschia Bromthymol blue – Blue black This is a base. Window cleanerPhenolphathlein – Fuscia Bromthymol blue – Blue black This is a base. DishsoapPhenolphathlein – Colourless Bromthymol blue – Yellow This is an acid C. You found a sample of a solution that has a faint odor resembling vinegar.
You are verifying that it is indeed vinegar and you add a few drops of phenolphthalein. The sample turns pink. What assumption can you make about this sample? Answer: I can assume that this solution is a base. D. While performing a starch test on several different cookie brands, four tests result in the typical black color of starch-presence, but the fifth gives a yellow-brown color. How might you interpret this result? Answer: In my interpretation, I would say that the first four cookies are primarily made of starch and the fifth cookie is not primarily made of starch.
E. You decided to investigate if the new wave of Vitamin Water is pH neutral: neither too acidic nor too basic. Using BTB (bromothymol blue), you select five flavors of Vitamin Water to test. Three of the flavor-samples turn a murky green, indicating the likelihood of acid/base balance. Of the two remaining, one turns slightly yellow, while one remains blue. What can you assume about the acid/base content of these particular flavors of Vitamin Water? Answer: I can assume that the two remaining Vitamin Water flavors are not neutral.
The liquid that remained slightly yellow is more acidic than alkaline, while the other liquid that remained blue is more alkaline than acidic. F. You have read that a new brand of hair tonic is supposed to contain lead (an ingredient in Grecian Formula). Devise a simple test to confirm the presence or absence of lead in that hair tonic. Answer: I would add KI to the hair tonic. If the product turns yellow, then the product has lead, if it does not, it does not contain lead. Conclusion: In conclusion, this experiment exposed how to perform, observe and interpret a variety of chemical reactions between substances used in household products.
The diluting phase prior to the commencement of the lab, clarified what is necessary to be done if a substance had excessively molarity. Macroscopic views of the chemical reactions were observed primarily through visual observation. Based on the visual observation, the outcome produced between the combined chemicals depicted whether or not a chemical alkaline or acidic or where a chemical is in the solution or not. It was quite interesting to see different reactions depending if it was placed on white paper or black paper and what occurred when sunlight or light was added to one reaction.
On the microscopic level, it is assumed that the rearrangement of atoms occurred when the chemicals combined with each other. In addition, since all molecules were different, the products created are compounds. The errors in this lab could be seen in the ratios of each substance. Although precaution was taken when cutting the pipet stem horizontally and ensuring the pipet was horizontal when a drop was squeezed out, it is hard to control and calculate the exact amount of liquid that expelled out of each pipet. In other words, 1:1 ratio may never have been exact