Researching Chemistry Flashcards
What are the types of Titrations
acid-base
redox
complexometric
How to determine the end point of an acid base titration
use indicator with relevant pH
How to make a primary standard
calculate mass of primary standard required
weigh standard by difference approximately and then accurately in a standard flask
add small vol of deionised water in a standard flask until it dissolves
Transfer to standard flask
add rinsings
stopper and invert
Characteristics of a primary standard
high purity - if not, solution would have lower conc
be stable in air and solution - true conc < calc. value
readily soluble in solvent - conc not as expected
large GFM - large uncertainty in mass weighed out
Examples of a primary standard
sodium carbonate
hydrated oxalic acid
potassium iodate
What are accurate results
in close agreement with the true/ accepted value
what are precise results
in close agreement with each other
What is the DILUTION calculation
C1V1 = C2V2
What to do if the dilution question is ION SPECIFIC
multiply unknown value by number of ions in the formula
What is the use of a control
to VALIDATE an experiment
Steps to a BACK TITRATION
Use titration calculation to calculate number of moles of formula IN BOTH CALCULATIONS
ratio it to SUBSTANCE ASKED
Work out actual moles and subtract value from answer 2
Scale to 1 mole
work out mass
What is gravimetric analysis
determining the mass of an element in a compound by PRODUCING A PRECIPITATE
What does a desiccator do?
prevents sample from absorbing water in air
-DOES NOT REMOVE WATER FROM SAMPLE
How to work out the value of a substance in a hydrated compound
work out the mass of water after evaporation
calculate moles of salt and water
calculate ratio
How are organic compounds prepared
through REFLUX
Methods of isolation
vaccum filtration (solids)
distillation (liquids)
solvent extraction (when the other 2 aren’t possible)
How to prevent substance boiling over when heating under reflux
anti- bumping granules
Techniques used for purification
Recrystalisation
Distillation
Techniques used to identify a sample:
melting point
boiling point
TLC
What is recrystallisation used for
to purify solids based on solubility
Reasons for Reduced % yield
loss of product / mass
side reaction
incompletion of experiment (equilibrium)
What if a substance has loads of impurities
Low MP
What if a substance has little impurities
High MP
Small temp change
Rules to remember for solvent extraction
more soluble in new solvent than current solvent
solvents must be IMMISCIBLE (like water and oil)
what is the purpose of a dessicator
prevent reabsorption of water
3 funnels for vacuum filtration
Buchner
Hirsch
Centred glass
