Laboratory Techniques Flashcards
What do you do when in decanting?
decant - pour the liquid off the solid and leave the solid behind
Separation of the precipitate from the supernate
regular filtration vs decantation techniques
Regular filtration: filter paper - wash precipitate (wash solution) - collect precipitate into filter paper
Decantation: supernate is separated from the precipitate which lies in the original vessel (don’t transfer precipitate into the filter paper)
Titration techniques:
preparation of burette
wash burette with detergent solution, … rinse with distilled water
rinse with the solution to be used
fill with solution (adjust to zero mark)
Difference between acid and base burette + combination
acid: has glass stopcock
base - has rubber tubing with a pinchcock
both: with Teflon stopcock
Titration technique
Deliver dropwise while continuously swirling the flask
Dominant hand: swirl
Left hand” open/close stopcock
Use white background
how to fill the burette
use funnel, remove air bubbles by opening stopcock for few second, refill (lower meniscus)
Test for basicity/acidity
watch glass - moisten litmus paper by stirring rod
red-blue: basic
blue-red: acidic
pH paper - color wheel
Measurements 1 ml few drops several drops pinch
20 drops
1-2 drops
3-6 drops
0.10-0.15g, spatula, mongo bean
how to weigh solid
use watch glass, calibrate
how to read measurement in liquid
read lower meniscus at eye level to avoid parallax error
how to use measuring pipette
use aspirator (dominant hand) - index finger
How to heat solutions in a test tube
use hot water bath: test tube submerged
how to get solid reagent
use spatula - watch glass
add reagent from watch glass by spatula
how to mix
less than .5
greather than .5
upright roll (don't cover) transfer to beaker - stir with glass rod (don't touch the sides of the beaker)
how to smell vapors
few inches away from you - waft
