chlorinity/floridity lab Flashcards
(8 cards)
why do we add an indicator
The dye molecules in the solution adsorb to the surface of the precipitated silver chloride (AgCl) particles, allowing us to detect the endpoint of the titration.
why do we calibrate with standard sample
Since the endpoint of the titration does not coincide exactly with the equivalence point (where all chloride ions have reacted), we calibrate the method using a sample with known salinity (and therefore known chlorinity). This helps account for any systematic error or deviation between the equivalence point and the endpoint.
why do we use the standard addition method
This method corrects for matrix effects by adding known fluoride amounts directly to the seawater sample and calibrating the response.
why do we use the ion selective electrode
The ISE measures the fluoride concentration by detecting the electrochemical potential difference across a lanthanum fluoride membrane.
why are we using an e cell
The total measured voltage (Ecell) is related to fluoride activity via the Nernst equation, accounting for reference potentials and minor asymmetry effects.
why do we have to determine erp uncertainty
to be able to quantify any of the systematic errors
why do we note the purity of the reagent
impurities can introduce unknown contaminants that affect reaction outcomes, alter concentration calculations, and introduce systematic errors in analytical measurements.
