Piedmont Hills High School - AP Chemistry Phan, Madalyn Period ⅘ , Laboratory Experiment : Buffer Lab PURPOSE The purpose of this lab is to find the answers to the questions: which buffer is more effective, a low concentration buffer or a high concentration buffer, which is more effective, a buffer with equal concentrations or one with different concentrations, and can a buffer can be made from a solution of a strong acid and its salt. BACKGROUND INFORMATION A buffer solution is a solution that resists changes in pH when small quantities of acid area added to it ( ). These solutions are made up of either a weak acid and its salt or a weak base and its salt ( ). In our experiment, most of the buffers that we prepared are made up of a weak acid and its salt, specifically acetic acid and sodium acetate. We made a total of fours buffers. The first buffer we made was a high concentration buffer; 0.65 M of both acetic acid and sodium acetate, with a pH of 4.74. The second buffer was a low concentration buffer; 0.33 M of both acetic acid and sodium acetate, with a pH of 4.74. The third buffer was a buffer containing different concentrations of the acid and salt: 0.65 M acetic acid and 0.33 M sodium acetate, with a overall pH of 4.45. The last buffer was one made of a hydrochloric acid and sodium chloride, strong acid and its salt. This buffer has a concentration of 0.26 M and a pH of 0.60. The strength of the buffer depends on the buffer capacity. Buffer capacity is a measure of the efficiency of a buffer in resisting changes in pH. Normally, the buffer capacity is expressed as the amount of strong acid or base that must be added to 1 liter of the solution to change its pH by one unit. ( ). In other words, a buffer with a high capacity is most effective because it can consume the most hydrogen or hydroxide ions and still not faze the pH. In order to test the strength of the buffers, we used a pH meter to measure the change in pH after adding a strong acid or base. A pH meter is an instrument used to measure acidity or alkalinity of a solution - also know as pH. pH is the unit of measure that describes the degree of acidity or alkalinity and is measured on a scale of 0 to 14 ( ). The strong acid we used was HCl, which is one of the seven strong acids and completely ionizes in solution ( _acids/revision/1/ ). The strong base we used was solid sodium hydroxide, which is an alkali
Piedmont Hills High School - AP Chemistry Phan, Madalyn Period ⅘ , Laboratory Experiment : Buffer Lab hydroxide and completely ionizes in solution ( ).
- Fall '13
- pH, Phan, Madalyn, Piedmont Hills High School