基础化学精品教学（广西医科大学）Experiment 3 Preparation and Properties of Buffers and Measure the pH of the Solution.doc

Preparation and Properties of Buffers and Measure the pH of the Solution 【Purposes】 (1) To grasp the properties of buffer solutions and effect factors of buffer capacity (2) To learn how to prepare a buffer solution and use the measuring pipette (3) To learn how to determine the pH values by using pH test paper and pH-meter 【Pre-lab Assignment】 (1) What is difference between a common solution and buffer solution? Why does the buffer solution have a buffer action? (2) What are properties of a buffer solution? On what factors does pH of a buffer solution depend? (3) How to determine the buffer capacity of a buffer solution? On what factors does buffer capacity of a buffer solution depend? (4) How to detect the pH change of a buffer solution? (5) According to the testing method, is this experiment a quantitative, qualitative or half quantitative analysis? (6) Use flowcharts to illustrate the experimental steps for this experiment, which can verify the properties of the buffer solution and the influencing factors of buffer capacity? In the flow chart, please indicate the important tips for each experiment step. 【Principles】 A buffer solution is defined as a solution that resists a change in pH when a small amount of acid or base is added to it or when the solution is properly diluted. The buffer solution consists of a weak acid (HB) and its conjugate base (B?). This experiment is designed to compare the buffer actions of a general solution and a buffer solution, by determining the change in pH when adding acid, base, or appropriate amount of H2O , helping people understand the properties of the buffer solution. The pH value of the buffer solution can be calculated by the following equation: Ka is the acid ionization constant, is buffer ratio. Buffer capacity designated as β is connective with total concentration of the solution (ctotal = [HB] + [B-]) and the buffer ratio ([B-]/[HB]). The greater the total concentration is, the greater the value of β is. The closer