General Chemistry II Experiments (with Qualitative Analysis)

Transcription

1 General Chemistry II Experiments (with Qualitative Analysis) The Laboratory Manual for Ch12 2 ND Edition Department of Chemistry Ateneo de Manila University Edward T. Chainani Ian Mitchelle S. de Vera Marites J. Pasuelo Deniz P. Wong 2008

2 Table of Contents ii Page No. Preface to 2 nd Edition Preface to 1 st Edition To the Student iii iv v The Experiments Expt 1: Chemical Mastermind 1 Expt 2: Surface Tension 5 Expt 3: Freezing Point Depression 9 Expt 4: Rate of Reaction: Concentration and Temperature 12 Expt 5: Le Chatelier s Principle 15 Expt 6: Preparation of Buffer 19 Expt 7: Titration of Acids and Bases 23 Expt 8: Introduction to Qualitative Analysis 28 Expt 9: Heat of Formation of Solid NaCl 42 Expt 10. Quantitative Analysis: Determination of Iron by UV-Visible Spectroscopy 45

3 Preface to the 2 nd Edition iii Several modifications were made to the 1 st edition, particularly in the qualitative analysis experiments. Instead of performing five separate experiments for the four cation groups and the anions, an abridged version encompassing five qualitative analysis experiments in the previous edition was considered. The rationale for this change is to give the student an overview of all the qualitative tests and develop the necessary laboratory skills without compromising the limited time for laboratory experiments (3 lab sessions instead of 5 for qualitative analysis). Moreover, the student will be given an impression that Ch12 is not mostly qualitative analysis but a continuation of General Chemistry I (Ch8). Two new experiments pertinent to General Chemistry II were also added: Surface Tension and Le Chatelier s Principle. These experiments were adopted and modified from: Surface Tension Sime, R. J. Physical Chemistry: Methods, Techniques, and Experiments (Saunders, 1990). Le Chatelier s Principle Brown, T., LeMay, E., Bursten, B. Chemistry: The Central Science 8 th Ed. Prentice Hall: New York, Grant, A., J. Chem. Educ. O466 (1984). Price David, Chromate-Dichromate Equilibrium. Taken from on December 11, 2007 We would like to acknowledge Ms. Christine Querebillo and other Ch12 teachers who tried the new experiments in their respective classes and gave invaluable inputs to improve the procedures employed in these experiments. Special thanks to Ms. Natasha Teran for helping us develop the Le Chatelier s Principle experiment. IAN MITCHELLE S. DE VERA DENIZ P. WONG ATENEO DE MANILA UNIVERSITY May, 2008

4 iv Preface to the 1 st Edition This manual is intended for the laboratory course (Ch 11) that accompanies the General Chemistry 2 lecture course. The regular semester allows for 9 or 10 experiments. In this manual is a selection of 11 such experiments. The experiments in this manual have been taken, with modifications, from the following: Laboratory Experiments: Chemistry the Central Science. Nelson, John H. and Kenneth C. Kemp New Jersey, Prentice Hall, Inc. Modern Experiments in General Chemistry. Schmitt, William J. and Salvador L. Balalta Quezon City, Philippines. Ateneo de Manila University. We have selected a couple of introductory experiments, for the benefit of those students for whom this is the first laboratory course. Keeping in mind that some students might have no other exposure to analytical techniques, we have included both classical and instrumental analysis methods. We would like to acknowledge the valuable suggestions and comments of Ricardo Borja, stockroom head of the Chemistry Department. We would also like to thank our students of several semesters of Ch 12, as well as the teachers of Ch 11 / 12, both of whom have helped us in improving the experiments. MARITES PASUELO EDWARD CHAINANI ATENEO DE MANILA UNIVERSITY 2002

5 v To the Student Chemistry is an experimental science. It will be much easier to appreciate and comprehend the science of chemistry if you actually participate in experimentation. You will find that laboratory work to be interesting and very rewarding if you have the patience to develop good technique, the honesty to report results as you obtain them, the initiative to deal with situations which are not covered in the text, and the aptitude to think about the meaning of the results in the light of the chemical principles behind it. Laboratory Safety and Behavior The experiments contained in this manual have been thoroughly tested, and are safe when performed properly, but there is always an element of danger (the same can be said for an automobile). Proper behavior and proper technique in the lab will help avoid any mishap. Take heed of any special precautions to be observed in an experiment that will be pointed out to you. Your teacher will outline the rules of behavior that you are expected to follow, but keep in mind that all rules are based on common sense: Do nothing that would interfere with the work of your neighbors. Clean up any spill. Report anything not functioning properly. Leave your work area clean when you finish. Preparation The lab instructor is there to guide you. Don t be afraid to ask questions. However, the lab periods are only long enough to do the experiment: there will not be enough time if you come to the laboratory unaware and have to figure out what you have to do. You should read the experiment procedure well in advance so that you can get the most out of the lab. As you progress in your

6 vi proficiency in the lab, fewer directions will be given. It helps to make an outline of the procedure and plan in detail what you must do to perform the experiment. Laboratory Reports Keeping a proper laboratory record is a vital aspect of good laboratory practice. Write down the data in your lab notebook as soon as it is obtained. If you make a mistake do not obliterate your mistake, but instead draw a simple line through it and write the correction beside it. You should always be able to read what you had written the first time. The workbook format of this manual provides data sheets for each experiment and guides you as to what must be recorded. The consistent tabular format is there primarily to help the teacher check numerous (30 or more!) reports more efficiently. We hope that you, like a welltrained scientist, will not limit yourself to putting down only the data required by the data sheet, but that you make use of blank spaces to take note of any other information that you judge to be relevant to the experiment.