Titration definitions

Background

 

PPE Personal protective equipment
Accuracy The proximity of a measurement to the true value, or the average of measurements
Precision Repeatability = how close a set of measurements are to each other
Outlier When a measurement is not in concordance with the other measurements
Concordant When pieces of data are very close in value (<0.1 mL difference)
Average of concordant (why) Average is more accurate; removes or mitigates some errors such as accuracy or measurement errors
Aliquot Taken using a pipette, it is a small sample of a solution used for titration
Primary standard essentials
    1. Known purity (preferably high)
    2. Known formula
    3. Soluble in water
    4. Neither deliquescent nor hygroscopic
    5. Does not react with the oxygen in the air
    6. Preferably a high molecular mass, to assist in accuracy during calculations
Primary standard A solution with the above qualities used to determine the concentration of other solutions through titration
Secondary standard A solution whose concentration is determined using the primary standard, not necessarily having all the qualities of a primary, for use in titration.

 

Titration

 

Titrant The liquid in the burette – name.
Titre The amount of titrant used to reach the endpoint (usually mL).
Analyte The solution being analysed in the flask
Flask [why?] Safety; the neck of the flask stops solutions from splashing, improving accuracy
Aliquot Using a pipette, it is a portion of a solution used in titration
Endpoint When the indicator changes colour, and the titration has stopped
Equivalence point When the solutions have been mixed in exactly the right molar proportions for a complete reaction
Partial drops [why?] To increase accuracy by dividing drops into parts. Squirt it off using distilled water.
Remove bubbles Bubbles cause significant error in volume
Adding distilled water to flask
Stop cock left hand around [history, why?] Taps made of glass, leaves hand free
Clean Remove any substances from the glassware
Rotate to clean To be able to reach all the sides of the equipment
Rinse 3 times To ensure that all other substances are removed
Burette funnel Smaller, lighter than normal funnels. Better for titration.
Fill With the titrant to above 0, then drain
Graduations on burette 0.1 mL – Concordant measurements must be within 0.1 mL
Precision of reading 2 decimal points (estimate the last one)
Meniscus Take reading from the bottom of the meniscus
One drop indicator Indicator reacts with analyte, so use as little as possible
Analyte white background So you can see the colour change more easily
Black line behind burette So you can see the bottom of the meniscus more clearly
Swirl flask To mix the solution; homogenise it
Colour change must persist for 10 seconds, then disappear
Rough titration Determine the approximate volume needed, so that subsequent measurements can be more accurate. When you get close to the rough volume, slow down the rate of titration to drops and partial drops.

 

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