Ph and Buffers Lab

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Buffers, and pH, and Diffusion oh my
The pH of a solution is the measure of the concentration of charged Hydrogen ions in that given solution. A solution with a pH lower than seven is considered to be acidic. A solution with a higher pH is a base. It is very important for organisms to maintain a stable pH. Biological molecules such as proteins function only at a certain pH level and any changes in pH can result in them not functioning properly. To maintain these constant pH levels, buffer solutions are used. A buffer solution can resist change to small additions of acids or base’s. A good buffer will have components that act like a base, and components that act like an acid.

Diffusion is random movement of molecules or other particles, resulting in even distribution of particles when no barriers are present (David Sadava, 2011). Diffusion always occurs from areas of high concentration to areas of low concentration, and leads to uniform distribution of solutes. Molecular weight plays a large role in diffusion.

The first experiment we did was to simply test the pH of white grape juice, 7-Up, white wine, seltzer water, milk of magnesia, sodium bicarbonate, and Maalox. We hypothesized that the white grape juice, 7-Up, white wine, and seltzer water would be acidic while the others would be basic. This is because I know that the more acidic 7-Up and white grape juice have been known to rot and corrode teeth.

The second experiment we conducted was to test for chloride ions and starch. We did this by adding drops of silver nitrate and iodine to Sodium Chloride, starch and distilled water. Our hypothesis for this experiment was that the silver nitrate would react in some way with the sodium chloride and the starch, but not with the water.

The third experiment we conducted was to test the buffer zone of a buffer solution. We used a 2 pH buffer solution and steadily added hydrochloric acid, then sodium hydroxide as a base. Our hypothesis was that we would reach the buffering potential with the hydrochloric acid but the sodium hydroxide would be buffered out and wouldn’t show significant change in pH. The next experiment we did was to test the diffusion of ions through an agar solution. We filled four holes in the agar with silver nitrate, sodium chloride, potassium bromide, and potassium ferricyanide. We hypothesized that the potassium ferricyanide would diffuse the furthest away from its origin, then silver nitrate, then potassium bromide, and the sodium chloride would diffuse the least. This is because the molecular weight of potassium ferricyanide is much great than that of the other molecules and smaller, lighter molecules diffuse faster than larger, heavier ones. The last experiment we did was to test the diffusion of starch and sodium chloride solution through a dialysis bag that is submerged in water. Due to the massive size of starch molecules I hypothesize that when we add iodine to the water no reaction will occur. However, when we add silver nitrate to the water with the sodium chloride dialysis bag we will see the same reaction we got in the test tube.

For the first experiment we poured white grape juice, 7-Up, white wine, seltzer water, milk of magnesia, sodium bicarbonate and Maalox into separate test tubes. We then took our digital pH reader and tested each substance for its pH making sure that we wiped off the electrode thoroughly before we tested each solution. We then recorded our results in a graph.

For the second experiment we filled six test tubes: two with 10ml starch (using pipets), two with 10 ml sodium chloride, and two with 10 ml of distilled water. We then added three drops of iodine to each solution and observed its results. We then added silver nitrate to each solution and observed its results.

In the third experiment we put 40 ml of a 2 pH buffer solution into a beaker and out it on a mixing platform. We then added 1 ml of HCL then recorded the pH. 1 ml of HCL...
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