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LABORATORY SAFETY RULES






A chemical laboratory can be a hazardous place to work if common safety rules are not enforced. If basic rules are strictly enforced, the chance of one being injured becomes very small. When working you will still need to use electric equipment, hot water, and concentrated solutions. These are only safe to work with if you follow the correct procedures. With proper understanding of what you are doing, careful attention to safety precautions, and adequate supervision, you will fi nd the chemical laboratory to be a safe place in which you can learn much about chemistry.

Some general precautions and procedures applicable to any chemical laboratory are summarized below.

1. Be prepared to work when you arrive at the laboratory. Read the experiment BEFORE you come to lab. Make sure you fully understand the experiment before starting the actual work. If you have a question, ask your professor/teacher/laborant for clarification BEFORE starting the procedure.

2. Carefully follow directions, both written and oral. Do only the steps described in the procedure of the experiment or that are described and/or approved by the teacher. If you are in doubt about any procedure, ask your teacher for help.

3. Everyone should be alert and proceed with caution at all times in the laboratory. Take care not to bump another student and to remain at your lab station while performing an experiment. An unattended experiment can result in an accident.

4. Wear safety glasses/goggles whenever you are in the lab. Aprons are required for some experiments. You may wear aprons at your discretion for any experiment to avoid staining or ruining your clothing.

5. A lab coat must be wear. Protective gloves should be worn whenever the potential exists for contact with toxic chemicals. Shorts and sandals are not safe lab attire, since they provide no protection from splashed or spilled materials. Bare feet are absolutely forbidden in the laboratory. To avoid entanglement with laboratory equipment, necklaces and bracelets should not be worn.

6. Locate the emergency evacuation plan posted by the door. Know your exit routes!

7. Locate emergency eyewash station, fire extinguisher, fire alarm, and fire blanket.

8. Dispose of all broken glassware in the proper receptacle. Never put broken glass in the trash can.

9. Do only the experiments that have been assigned by your teacher. No unauthorized experiments will be allowed.

10. Notify your instructor immediately if you are injured in the laboratory; no matter how slight.

11. NO FOOD OR DRINK IS ALLOWED IN THE LABORATORY. Never put anything into your mouth while you are in the laboratory. Eating, drinking, and smoking are strictly forbidden in the laboratory!!! Never pipette fluids by mouth. Check odors cautiously. Never taste a chemical.

12. Shoes must be worn in the laboratory. These shoes must fully enclose your foot.

13. DO NOT WEAR CONTACT LENSES IN THE LABORATORY!!! Approved eye protection (safety glasses with side shields or goggles) must be worn at all times in the laboratory. Contact lens must never be worn because they can trap corrosive, volatile materials which may damage the eye.

14. Long hair must be tied up in a bun during lab work. Loose long sleeves should be avoided in the lab. It is a fire hazard!!!

15. Children and pets are not allowed in the laboratory.

16. Do not drink from the laboratory glassware.

17. Wash your hands before and after working in the lab.

18. Turn off all burners when you are not using it.

19. If any reagents are spilled, notify your instructor at once.

20. Follow the instructors directions for disposal of chemicals.

21. All reactions using or evolving noxious or combustible chemicals must be performed in the fume hoods.

22. Every chemical in a laboratory must be properly labeled. If a label is unclear, do not use them, notify your instructor.

23. Use the proper instrument (eye-dropper, spatula, etc.) to remove reagents from bottles. Never return unused chemicals to the original container. Do not cross contaminate reagents by using the same instrument for 2 different reagents. (e.g. dont use the mustard knife in the mayonnaise jar).

24. If you cut yourself, spill a chemical on yourself, or receive a burn by touching a hot object, run cold water over the affected area, and you or your partner notify your teacher immediately.

25. Clean up spills. Spills of chemicals or water in the work area or on the floor should be cleaned up immediately. Small spills of liquid can be cleaned up with a paper towel. Use Sodium Bicarbonate to neutralize an acid spills. Use boric, citric or acetic acid to neutralize base spills. Mercury spills require special attention. Notify your professor if you break a thermometer so that special methods can be used to remove the mercury.

26. If a substance is splashed in your eyes, immediately use the eye wash fountain or a water faucet to rinse your eyes. This should not happen if you are wearing goggles.

27. Does not taste, touch, or smell any reagents unless directed to do so by your teacher. When smelling chemicals or gases, use a wafting motion to direct the odor toward your nose. When you are sniffing any substance keep container at least 15-20 cm from your nose.

28. If your clothing should catch fire, stop, drop, and roll while your lab partner notifies the instructor. Before leaving the lab, check to see that all gas valves and hot plates are turned off.

29. Keep flammable and combustible materials away from open flames. Some examples of flammable materials include alcohol, carbon disulfide, and acetone.

30. When heating a substance in a test tube, be careful not to point the mouth of the test tube at another person or yourself.

31. Use caution and the proper equipment to handle hot objects. Cool glass looks just the same as hot glass. Heat only heat-resistant glassware (marked Pyrex or Kimax). Other glassware may shatter when heated. Be very careful of hot objects.

32. Handle chemicals carefully. Check the label of all bottles before removing the contents. Take only as much as your need. Do not return unused chemicals to reagent bottles.

33. Be careful of fires. Small fires can be extinguished by covering them with a watch glass. If a larger fire is involved, a fire extinguisher can be used. If clothing or hair catches on fire the rule is drop and roll to extinguish the flames.

34. Know the correct procedure for mixing acid solutions. ALWAYS add the acid slowly to the water . Never add water to an acid. During the preparation addition constantly stir the solution using a glass rod.

35. Never handle broken glass with your bare hands. Use a brush and dustpan to clean up broken glass. Dispose of the glass as directed by your teacher. Record and report all breakage or loss of apparatus to your teacher.

36. Work areas should be clean and tidy at all times. Only lab procedures, lab notebooks, pencils and sometimes calculators should be brought to the work area.

37. When an experiment is completed, always clean equipment and return it to the proper place. Clean your lab table after experiment.

38. Behave in a responsible manner while in lab. Be aware of the other students around you.

11.Theme: Coordination compounds. Classification, structure, nomenclature, properties.

 

Transition metal ions characteristically form coordination compounds, which are usually colored and often paramagnetic. A coordination compound typically consists of a complex ion, a transition metal ion with its attached ligands, and counter ions, anions or cations as needed to produce a compound with no net charge. Coordination compounds have been known since about 1700, but their true nature was not understood until the 1890s when a young Swiss chemist named Alfred Werner (18661919) proposed that transition metal ions have two types of valence (combining ability). One type of valence, which Werner called the secondary valence, refers to the ability of a metal ion to bind to Lewis bases (ligands) to form complex ions.

 

Structure of coordination compounds.

 

K4[Fe(CN)6] potassium hexacyanoferrate (II)

K4[Fe(CN)6] External sphere

K4[Fe(CN)6] Internal sphere

K4[Fe(CN)6] Central atom

K4[Fe(CN)6] Coordinate relation

K4[Fe(CN)6] Ligand

Central, complex forming, atoms is usually serves ions of metals of greater periods (Co, Ni, Pt, Hg, Ag, Cu). Typical ligands are OH-, CN-, NH3, CO, H2O; they connected with the central atom by donor-acceptor bound.

 

 

Coordination Number

The number of bonds formed by metal ions to ligands in complex ions varies from two to eight depending on the size, charge, and electron confi guration of the transition metal ion. Many metal ions show more than one coordination number, and there is really no simple way to predict what the coordination number will be in a particular case.

 

Ligands

A ligand is a neutral molecule or ion having a lone electron pair that can be used to form a bond to a metal ion. The formation of a metalligand bond therefore can be described as the interaction between a Lewis base (the ligand) and a Lewis acid (the metal ion). The resulting bond is often called a coordinate covalent bond.

A ligand that can form one bond to a metal ion is called a monodentate ligand, or a unidentate ligand (from root words meaning one tooth).

Some ligands have more than one atom with a lone electron pair that can be used to bond to a metal ion. Such ligands are said to be chelating ligands, or chelates.

Preparation

Reactions of salts with ligands

AgCl + 2NH3 → [Ag(NH3)2]Cl

FeCl3 + 6KCN → K3[Fe(CN)6] + 3KCl

Chemical properties

1. Destruction of complexes at the expense of forming the slightly-soluble compounds

2[Cu(NH3)2]Cl + K2S → CuS↓ + 2KCl + 4NH3

2. The exchange of ligands between external and internal spheres

K2[CoCl4] + 6H2O → [Co(H2O)6]Cl2 + 2KCl

Naming Coordination Compounds

A complex is a substance in which a metal atom or ion is associated with a group of neutral molecules or anions called ligands. Coordination compounds are neutral substances (i.e. uncharged) in which at least one ion is present as a complex.

The coordination compounds are named in the following way.

. To name a coordination compound, no matter whether the complex ion is the cation or the anion, always name the cation before the anion. (This is just like naming an ionic compound.)

B. In naming the complex ion:

1. Name the ligands first, in alphabetical order, then the metal atom or ion.

Note: The metal atom or ion is written before the ligands in the chemical formula.

2. The names of some common ligands are listed in Table 1.

For anionic ligands end in " -o"; for anions that end in " -ide" (e.g. chloride), " -ate" (e.g. sulfate, nitrate), and " -ite" (e.g. nirite), change the endings as follows: -ide -o; -ate -ato; -ite -ito

For neutral ligands, the common name of the molecule is used e.g. H2NCH2CH2NH2 (ethylenediamine). Important exceptions: water is called aqua, ammonia is called ammine, carbon monoxide is called carbonyl, and the N2 and O2 are called dinitrogen and dioxygen.

12.Basic chemical laws. Chemical laws are those laws of nature relevant to chemistry.