Exp9 - Discussion The objective of this experiment was to...

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Discussion: The objective of this experiment was to explore the properties of pH through measurements and the analysis of data. The first part of the experiment consisted of measuring the pH of several common items and ranking them in order of decreasing acidity. The pH of most items that could be consumed ranged between 4 and 6, while the ones with pH outside this range were used for more intensive tasks such as cleaning. Out of all the items whose pH was measured, the most acidic was the toilet bowl cleaner due to the fact that it contains HCl as one of its ingredients. The most basic of all of the items was the clear ammonia because NH 3 is a basic molecule. The next part of the experiment consisted of measuring the pH of acids and bases with a concentration of 0.1 M and then measuring the pH of the same acids and bases after they have been diluted in 1:10 and 1:100 ratios. Out of the acids and bases given, HCl was a strong acid and acetic acid was a weak acid because it does not give off as many H + ions as HCl. Likewise the strong base was NH 4 OH and the weak base was NH 4 OH because the concentration of OH - ions is less in NH 4 OH than in NaOH. As these acids and bases were diluted by a factor of ten each time, the pH increased for the acids and it decreased for the bases because as the solutions became more diluted, the concentration of H + ions decreased which raised the pH. For the bases the concentration of OH - decreased which raised the pOH, which in turns meant that the pH must lower. For both, the percent dissociation increased because the concentration of the acid or base was lowered so each diluted ion counted more in the percentage calculations. The following part of the experiment dealt with the effects of CO 2 on the pH of aqueous solutions. To measure the effects of injecting CO 2 into water, the pH of de-ionized water was measured and then it was measured again after having KCl added to increase its ionic strength. The measured pH was used as a standard for comparing the pH after the injection of carbon dioxide by means of blowing into the solution with a straw. The pH of the solution decreased because the CO 2 reacts with the soda water to form carbonic acid, which then dissolves into H+ ions and HCO3- ions, and further into H + and CO 3 - ions. The increase in the concentration of H + causes the solution to be more acidic and lowers the pH. Henry’s law, which states that the amount of gas that can be dissolved in a liquid is directly proportional to the pressure on the liquid, plays an important role in this part of the experiment because the pressure on the liquid at that time, determines how much gas can be dissolved in it. When the soda is boiled the pressure inside the liquid increases so the pressure outside cannot keep the gas particles in the liquid so they escape and since the CO 2 is gone, no more acid can be formed so the concentration of H + is lowered thus raising the pH. This principle
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This note was uploaded on 03/08/2010 for the course CHEMISTRY 1310 taught by Professor Williams during the Spring '10 term at Georgia Tech.

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Exp9 - Discussion The objective of this experiment was to...

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