Experiments 1 Kinetics of reaction between Fe(III) and SCNˉ by the stopped flow technique 19
2 Vibrational-Rotational spectra of HCl and DCl 29 3 Thermodynamics of galvanic cells 33 4 Determination of heats of solution from solubility measurements 36
5 The partition coefficient – The equilibrium I- + I2 I3- 38 6 Magnetic susceptibility of solid transition metal compounds 41 7 The dipole moment of chlorobenzene 44
8 Viscosity: Molar mass of a polymer 48
9 Enthalpy of mixing of acetone and water 53
10 Viscosity of gases 57
11 Dissociation constant of CH3COOH from electrical conductivity 61
12 The rate of hydrolysis or inversion of sucrose by polarimetry 66
13 A complex reaction: The bromination of acetone 72 14 Dissociation constant of an indicator by spectrophotometry 77 15 Differential scanning calorimetry 80
16 Chemical Oscillations: The Belousov-Zhabotinskii Reaction 87
OCCUPATIONAL HEALTH AND SAFETY YOU are warned that all substances handled and all operations performed in a laboratory can be hazardous or potentially hazardous. All substances must be handled with care and disposed of according to laid down procedures. All operations and manipulations must be carried out in an organised and attentive manner.
In order to assist you in developing good and safe laboratory techniques, a set of Laboratory Rules and Regulations is attached. You are required to read these and to acknowledge that you have read and understood them. Additionally, in the laboratory manuals/practical books and/or pre-practical lectures your attention will be drawn to the correct and safe handling of specific chemicals/reagents/solvents, and to the correct/safe manner in which specified laboratory operations must be carried out. These specific instructions and/or warnings must never be ignored.
LABORATORY RULES AND REGULATIONS
1 Students must be present ten minutes before the start of each scheduled laboratory session. Latecomers will be refused entry to the laboratory.
2 No student will be permitted to work in the laboratory outside of laboratory hours except by express permission of the staff member(s) responsible for the session. Never work in a laboratory on your own.
3 Smoking is strictly prohibited in all laboratories and instrument rooms.
4 Do not put anything into your mouth while working in the laboratory. NEVER taste a chemical or solution. Eating is totally PROHIBITED in all laboratories.
5 All students are required to wear a laboratory coat and no student will be permitted to work in the laboratory without one. 6 All students who do not wear conventional spectacles must wear eye protection. Safety glasses must be worn throughout all practical sessions. Students who wear conventional spectacles must have them on at all times when in the laboratory. 7 All students must wear closed shoes in the laboratory, unless permission has been obtained to wear sandals for some medical reason.
8 Apparatus and chemicals are NOT to be removed from the laboratory.
9 Students will find the laboratory bench clean on arrival in the laboratory. The bench at which you work must be left clean when you leave the laboratory at the end of the practical session. Bench tops must be wiped clean. Glassware and other apparatus should be left clean and dry, unless otherwise indicated or instructed.
10 Work areas must at all times be kept clean, and free from chemicals and apparatus which are not required. All glassware and equipment must be returned to its proper place, clean and dry, and in working condition, unless otherwise indicated or instructed.
11 All solids must be discarded into the bins provided in the laboratory. Never throw matches, paper, or any insoluble chemicals into the sinks. Solutions and liquids that are emptied into the sinks must be washed down with water to avoid corrosion of the plumbing. Waste solvents must be placed into the special waste solvent bottles provided.
12 Before leaving the laboratory at the end of a practical session make sure that all electrical equipment is switched off, and that all gas and water taps are shut off.
13 Students who break or lose equipment allocated to them will be required to pay for replacements. All breakages or losses must be reported to the teaching assistant in charge.
14 Do NOT heat graduated cylinders or bottles because they will break easily.
15 Any apparatus or glassware which has to be heated must be heated gently at first, increasing the amount of heat gradually thereafter.
16 Balances, spectrophotometers and other expensive equipment must be treated with care and kept clean and tidy at all times.
17 Fumehoods must be used when handling toxic and fuming chemicals. Other operations, such as ignitions, are also carried out in fumehoods. The only parts of the human body which should ever be in a fumehood are the hands - never put your head inside a fumehood.
18 Never leave a laboratory experiment unattended without first consulting the TA in charge.
19 Reagent bottles must be re-stoppered immediately after use. It is absolutely forbidden to introduce anything into reagent bottles, not even droppers. Solutions and reagents taken from bottles must NEVER be returned to the bottles. Do not place the stopper of a reagent bottle onto an unprotected bench top.
20 Laboratory reagents and chemicals must be returned to their correct places immediately after use. Spillage must be cleaned off bottles/containers. Labels must face the front.
21 The use of reagent bottle caps as weighing receptacles is forbidden.
22 Liquids - whether corrosive or not - must be handled with care and spilling on the bench or floor should be avoided. Any spillage must be cleaned up at once - if the liquid is corrosive (acids or bases) call your TA or professor. Never hold a container above eye level when pouring a liquid.
23 When carrying out a reaction or boiling a liquid in a test tube, point the mouth of the test tube away from yourself and others in the laboratory.
24 Beware of hot glass and metal. Never handle any item which has been in a flame, a hot oven or a furnace without taking precautions. Use leather/asbestos gloves or tongs, or ask for advice on what to use.
25 Report all accidents, cuts burns, etc., however minor, to your TA or the professor. Eye-wash stations are located in various places in the laboratory. Ensure that you know where the nearest one to your bench is located.
26 A chemical laboratory is not a place for horse-play. Do not attempt any unauthorised experiments. Do not play practical jokes on your classmates. Such things are dangerous and can cause serious injury. Any student found indulging in such activities will be banned from the laboratory, with consequent grade of F for the lab course. GENERAL FIRE ORDERS
Fire fighting instructions are exhibited in individual laboratories. However, the following orders must always be obeyed.
In the event of a fire Attack it at once with the appropriate fire fighting equipment and shout for help.
On hearing a fire evacuation alarm 1 Stop normal work immediately.
2 Make safe any apparatus, and material in use, shutting off as necessary any local gas taps/valves, electricity and other potentially dangerous services under your control.
3 Immediately leave the building.
4 Go to the Fire Evacuation Area which for this CHEMISTRY BUILDING is outside to the south west entrance to the building, on the grassed area between the Hall of residence and Science Building 2 (which is the building you are presently).
DEPARTMENT OF CHEMISTRY
PORTLAND STATE UNIVERSITY
I, the undersigned (please print full name)
Student No. ........................................
Identity No. .......................................
do hereby acknowledge having read and understood the documents headed "Occupational Health and Safety" and "Laboratory Rules and Regulations". Furthermore, I accept that contravention(s) of these rules and regulations will lead to my expulsion from the laboratory.
I agree to abide by any additional laboratory regulations or safety rules presented in writing in the practical manuals/books or issued verbally by the INSTRUCTOR-in-charge, or his/her responsible member of staff.
SIGNED ........................................... DATE .......................
ARRANGEMENTS FOR LABORATORY SESSIONS
Dates and Times for Practical Sessions
Practical sessions will be held only on the specific timetabled day during the winter quarter.
Laboratory sessions will commence promptly. Students are expected to report punctually for each laboratory session. Those arriving late for a practical session may not be admitted to the laboratory. This will result in a mark of zero being recorded for that experiment.
A register will be taken each day, and a grade of F may be awarded to students whose attendance records are regarded as unsatisfactory. Each experiment will be marked out of 100; a mark of 0 will be entered in the case of an uncondoned absence. Absences will only be condoned for medical reasons; in such cases a medical certificate must be provided at the next lab session.
Students must wear white laboratory coats and safety glasses at all times while in the laboratory. Open shoes and flip-flops are not considered acceptable dress. The wearing of any headgear in the laboratory is also unacceptable. Sunglasses are not to be worn as a substitute for safety glasses.
Any accidents which occur during the laboratory session must be reported immediately to the professor in charge, who is required by law to write an accident report.
Any breakages of equipment or glassware must be reported immediately to the TA in charge. The costs of replacement will be debited to the student's fee account.
Certain experiments generate hazardous waste which must be disposed of according to the instructions provided in the laboratory manual or given by the lecturer in charge.
Students are required to have a hardcover notebook in which to write their laboratory reports. Some may prefer to have two lab notebooks so that they can still have one with them after submitting one for grading. These lab notebooks are available in the bookstore. All relevant data, measurements and observations, should be written directly into the lab notebook, and not on some scrap pieces of paper and they transcribed into the lab notebook after the lab session. It is not essential that the lab notebook be clean and neat. Nothing wrong with well-arranged data presentation in a student’s notebook, but this can be more of a product of preparation prior to the session.
Pre-practical Preparation and Report Writing
The key to doing these practicals correctly and expeditiously is your preliminary preparation before coming to the lab session!!
Before coming to the laboratory you should have stated the aim of the experiment you are about to perform that afternoon in your laboratory notebook. In addition, you should have prepared the tables (with the columns appropriately headed) into which you will enter the data you collect during the practical.
The crude data collected during the laboratory session must be entered directly into the notebook, in ink, in tabular form where appropriate. Each table should contain the appropriate columns of data, each column consisting of a particular physical property. As a physical property is the product of a number and a unit, the heading of each column should consist of the property divided by its unit, so that the entries in the column below are pure
numbers, as shown in the example below.
Likewise, graphs should be included in the report where appropriate. In plotting graphs, students should use graph paper (provided at the front desk) and utilise the full area of the sheet of graph paper, adjusting the scales on the axes to maximize the space available. Measurements of the gradients of graphs should be performed by using the largest possible spread of values along the horizontal and vertical axes, in order to minimize errors in determining the slopes. The axes should be labelled clearly with the properties being plotted, along with their units, in the same way as for the column headings in tables, as shown in the attached example (page ix). The same applies to graphs prepared with a computer package such as Microsoft Excel®.
For the example of a typical graph shown in Figure 1;
Calculationsmust be shown in full; for repetitive calculations of the same type, it is only necessary to include one full set of workings.
Each report should end with a discussion, in which students are expected to remark on the significance and meaning of their results, and explain any unexpected observations which may have been made. For several experiments the laboratory manual sets a number of questions which should be answered as part of the discussion in the report. This is the most creative part of the report, and presents the opportunity for students to score marks for demonstrating their understanding of the experiments performed and the relevance of their results. A copy of the Handbook of Chemistry and Physics is provided in the laboratory, and students are expected to consult this reference work in order to compare their results with those in the literature, and to cite a reference for any value quoted. Relevant comments on possible causes for significant deviations of their results from those in the literature should also be included in this section of the report.
Note: Read the first 89 pages Garland, Nibler and Shoemaker, Experiments in Physical Chemistry, Seventh Edition.
The references given in the detailed instructions in this laboratory manual refer to the following two texts:
P.W. Atkins and J. de Paula, Atkins’ Physical Chemistry, 7th edition, Oxford University Press, Oxford, 2002.
Garland, Nibler and Shoemaker, Experiments in Physical Chemistry, Seventh Edition, McGraw-Hill, 2003.
Figure 1: Osmotic pressure of aqueous solutions of sucrose plotted as a function of concentration at 20 °C.