计算机模拟实验

1、计算机模拟实验计算机模拟实验 目的要求目的要求 近年来计算机模拟化学实验软件的发展十分迅速。 对一些危险性高或费用高或耗时长的实验，在计算机上“做实验”是一种十分理想的教学方法。 在化学的远程教育中，若学生受条件所限不能亲自到实验室中做实验，在计算机上“做实验”，是一种可行的解决办法。 本实验将使用Model Science Software公司的交互式化学实验模拟软件ChemLab来进行酸碱滴定实验。 通过本实验，要求能用ChemLab软件来进行实验的操作，同时掌握酸碱滴定的有关原理及应用，此外，由于该软件是英文版的，所以，要求能正确理解有关的英文。Acid-Base Titration W

2、ater dissociates (self-ionizes) into H+ (hydrogen ion) and OH- (hydroxide ion) ions naturally to a very small extent: H2O H+ + OH- In a neutral solution the concentration of H+ and OH- are equal at 1.0 x 10-7 M. An acidic solution is one in which the concentration of H+ OH-, and in an basic solution

3、 the H+ OH-. pH is a measure of the concentration of H+and is defined as: pH = -log H+ In a neutral solution pH = 7. A pH 7 signifies a basic solution. In this experiment we will explore the use of titration, adding small quantities of a base to an acid and recording the rise of pH. We can plot the

4、pH against the amount of base added producing a titration curve. The steepest point on the curve occurs at the equivalence point, when the acid is exactly neutralized. Because the titration curve is so steep near equivalence only a small amount of base can result in a large change in pH. This point

5、is the end point of our reaction and can be signified by the color change of an indicator. An indicator, in an acid base reaction, is a substance whose color changes over a particular pH range. Phenolphthalein is an example of an indictor which changes from colorless to pink as pH goes from 8 to 10.

6、 In this lab we will be using a strong acid and a strong base to perform our acid base titration. Strong acids and bases can be assumed to dissociate in water completely. We will be adding NaOH, a strong base, to HCl, a strong acid. The NaOH will neutralize the HCl in a reaction that produces sodium

7、 chloride (salt) and water: HCl + NaOH NaCl + H2O Since the stoichiometric ratio of hydrogen ions to hydroxide ion is 1:1 in this reaction, the number of moles of NaOH added to HCl will be equal at the end point or: (Molarity acid) (Volume of acid) = (Molarity of base) (Volume of base added)Procedur

8、e Step 1: Obtain acid, in a 100 ml Erlenmeyer flask add 35 ml of 0.2M HCl solution. Step 2: Add an indicator to the acid, select the flask and add 2 drops of phenolphthalein indicator. The indicator menu is available under the chemicals main menu (Chemicals/Indicators) or the context menu. Step 3: F

9、ill buret with NaOH, obtain a 50 ml buret and fill with 0.2M NaOH solution. Step 4: Titrate NaOH into HCl until end point, record initial buret volume and add NaOH (quickly at first then slowly) until the HCl solution turns pink and record the final buret volume of NaOH in buret. Step 5 repeat steps

10、 1-4 using pH meter, add a pH meter to the acid solution. Record several points of pH and NaOH added (especially near equivalence point) to be use later to prepare a titration curve. Observations: 1 fill the following form: initial buret volume: final buret volume: total volume titrated to reach end

11、-point: 2 What happened to the rise in pH as the end-point was approached? 3 With Origin Software, prepare a titration curve with pH on the y-axis and volume of base added on x-axis. Determine the equivalence point from the curve (steepest point of curve).dissociate离解 Plot绘图 experiment实验Ionize离子化 eq

12、uivalence等价，等值 Titration滴定Ion离子 Indicator指示剂 Quantity数量hydorgen氢 substance物质 Measure测量hydroxide氢氧根 phenolphthalein酚酞 Reaction反应Neutral中性的 E r l e n m e y e r flask锥形瓶 Lab实验室Solution溶液 Sodium chloride氯化钠 Buret滴定管concentration浓度 stoichiometric化学计量的 Initial开始的Acidic酸的 Mole摩尔 Meter表，仪器Basic碱的 Molarity摩尔浓度 Drop滴注意事项注意事项1 在打开chemlab软件时，菜单上会显示六 个 实 验 ， 注 意 选 择 A c i d - B a s e Titration。 2 实验报告要用英语完成。 3 要依据实验数据,用origin 软件画出滴定曲线图。 4 禁止不经