General Things to Know Flashcards
Recommended protective clothing for the lab
Safety goggles, footwear, long hair must be tied back, no food/drink
first aid used for chemicals on the skin, eye, and cut/abrasions/burns
- best course of action for chemicals splashed on skin is to flush with large quantities of tap water
chemicals in eye: locate the emergency eye wash to your station - use for a minimum of 10 minutes, inform instructor, after flushing, go to health services
cut, abrasions, and burns: report to TA
What types of things should you do in case of fire and explosions?
-learn the location of fire exit, alarm, extinguisher, safety shower and fire blankets-If the fire alarm sounds, turn off all services (gas, electricity, and water) and leave the building immediately via the exit indicated. Listen for additional instructions.
-In the case of a fire or explosion in the lab, evacuate the room and close the doors. Pull the nearest wall alarm and leave the building immediately via the exit indicated. Avoid inhaling smoke and gases resulting from fire or explosion.
-If clothing catches fire, stop where you are, drop to the floor and roll to smother the fire (DO NOT RUN)
-Assemble apparatus so that control valves and switches will remain accessible if a fire should occur. Do not set up so that it is necessary to reach through the assembly to turn water, gas or electricity on or off.
-Limit flammable liquids to amount actually needed for immediate use. The vapour of nearly all organic solvents is flammable. Keep open flames, electric sparks and heating elements away from solvents; prevent vapours from escaping by keeping lids closed.
What are the 3 different classes of fire extinguishers?
Multi-purpose Dry Chemical extinguishers (Type ABC) and may be used on Class A, B and C fires.
· Class A fires: ordinary combustible materials (paper, wood, most plastics)
· Class B fires: flammable / combustible liquids (gasoline, solvents, grease, oil)
· Class C fires: electrical equipment (appliances, wiring, circuit breakers, outlets)
How to operate a fire extinguisher?
· Pull the pin or locking device.
· Aim low, at the base of the fire.
· Squeeze the handle.
· Sweep slowly and evenly across the base of the fire.
When and only should you attempt to extinguish a fire?
· Everyone is leaving the room and someone is dialing 911 to call the fire department.· The fire is small, not spreading, and the smoke or heat does not pose a threat.
· Your extinguisher matches the type of fire you are attempting to fight.
· You have confidence in fighting the fire, and are familiar with use of the extinguisher.
-Don’t get trapped by fire always keep your back to a clear exit
What should you become familiar with before using a chemical?
before using a chemical, you should become familiar with the
- boiling point-flash point
- vapour pressure
- toxicity
- explosive limits
- incompatibilities and other special precautions
this info is available in the MSDS binders
Which creates most of the dangers in the lab?
- vapours
- nearly all chemicals are poisonous to the human body to some degree
- vapours may be toxic, flammable or both
- chemicals of these types should be handled in ventilated hoods in such a manner that the vapour will be carried away
Whats the difference between weight and mass?
- weight is mass x acceleration
- mass is a measure of the quantity of matter
What’s the difference between accuracy and precision?
Accuracy
- concerns the deviations of a measured or calculated value from the “true” value
- “true” values are usually just “accepted” values
Precision
- a measure of the reproducibility of an experiment and can be quantitatively expressed as an average or standard deviation
- precise isn’t always accurate as many errors in the measuring technique can be constant
Volumetric Pipette are accurate to:
-the volumetric pipette used in the first year chem lab are accurate to +/-0.01-0.03mL
mohr (graduated pipette)
- this type of pipette is never fully drained, as the tip is not calibrated its volume is not known
- slightly less accurate than volumetric pipettes because two readings are required (initial and final)
Describe use of a burette in a standardization titration
- can measure with a +/- 0.01 mL
1. rinse burette
2. fill burette
3. initial reading of burette
4. titration
Describe quantitative transfer of sample technique (solid)
- if a sample is in a single large chunk like a tablet or capsule, transfer can be accomplished by being picked up by clean, dry forceps and moved into the receiving vessel
- use of forceps prevents the contamination of the sample from moisture or oil on the analysts hands
- for a solid in a powdered or crystallized form the sample can be weighed on weighing paper, a weighing boat, or in a clean, dry beaker
- to use weighing paper, fold it in half then in half again to create a crease in the paper when unfolded and then place the paper on the balance such that it forms a concave surface for the sample
- once the sample has been weighed the sample can be transferred to a receiving vessel by carefully tupping the creased weighing paper and pouring the solid into the beaker
- tap the paper with a clean scoopula or stir rod to knock particles into the beaker
-the paper should then be rinsed with a small amount of the solvent being used to remove all traces of solid sample - if using a weighing boat it should be the same but once it’s been weighed it’s transferred by pouring it into the receiving vessel and then gets rinsed with solvent until no trace of solid remains, this might have to be done 3 to 5 times
Describe quantitative transfer of sample technique (liquid)
- when transferring a liquid rinse the dispensing vessel with solvent and transfer the rinses to the receiving vessel
- at least 3 rinses are recommended to ensure that none of the sample remains in the dispensing vessel
- if you use a funnel then the funnel needs to be rinsed with solvent and the rinses added to the receiving vessel
