P.P flashcards Volumetric Analysis ✓
(26 cards)
What is volumetric analysis?
A quantitative technique used to determine the concentration of an unknown substance.
What is a titration?
A method where a solution of known concentration is added to a solution of unknown concentration until the reaction is complete.
What is a volumetric flask used for?
Preparing standard solutions and diluting solutions to a known volume.
What is a burette used for?
Delivering a measured volume of titrant dropwise into a conical flask.
What is a pipette used for?
Accurately measuring and transferring a fixed volume of solution.
What is a primary standard?
A solid that can be made into a solution of precisely known concentration.
Name two common primary standards.
Anhydrous sodium carbonate and sodium hydrogen carbonate.
Define ‘endpoint’.
The point where the indicator changes colour, indicating the titration is complete.
Name two common primary standards.
Anhydrous sodium carbonate and sodium hydrogen carbonate.
Define ‘equivalence point’.
The point at which reactants are present in stoichiometric proportions.
What does a concordant titre mean?
Three titres within 0.3mL of each other
Why rinse volumetric glassware with distilled water before use?
To remove any contaminants that might affect concentration
Why rinse a burette or pipette with the solution it will contain?
To prevent dilution by leftover water, ensuring accurate concentrations
Why must the volumetric flash be filled so the meniscus touches the calibration line?
To ensure an exact volume for accurate calculations
Why is a base rarely placed in a burette and how can it affect volume measurements?
Because bases can etch glass, creating rough surfaces that trap liquid and slightly alter the volumes the burettes hold, leading to inaccurate readings
Why is it important not to remove the final drop from a pipette?
It is accounted for in the calibrated volume. Removing it would add extra volume
What indicator should be used for a strong acid-strong base titration?
Either phenolphthalein or methyl orange because both change near pH 7
How would you determine the concentration of an acid using titration?
-Use a base of known concentration
-Calculate moles of the base
-Use mole ratio to find moles of acid
-Then divide by acid volume
What indicates the endpoint?
The change of colour of the solution in the volumetric flask
Why are titration curves useful when colour change is not visible?
They allow you to determine the equivalence point using pH data
What do you do if you overfill a volumetric flask?
Discard the solution and restart. You cannot adjust it back to the line
How do you choose an appropriate indicator for a titration?
Match the indicator’s colour change range to the expected pH at the equivalence point.
Why does the number of moles stay the same when diluting a solution?
Because no extra solute is added
What is the titrant in a titration?
The solution in the burette with a known concentration
