which is used as std solution in estimation of hcl
Answers
Answer:
Pipette 25.00mL of HCl(aq) into a 125mL Ehrlenmeyer flask and add two drops of phenolphthalein indicator. Titrate this solution with NaOH(aq) to the endpoint. Calculate the concentration of the HCl(aq) stock
Answer:
general remarks
Determination of hydrochloric acid concentration is probably the most often discussed example of acid-base titration. Both acid and base are strong, which not only makes determination of end point easy (steep part of the curve is long), but also means that calculation of titration curve and equivalence point are pretty straightforward.
reaction
This is a simple neutralization reaction:
HCl + NaOH → NaCl + H2O
It is worth of noting, that - as we can assume both acid and base to be completely dissociated - net ionic reaction is just
H+ + OH- → H2O
which is the simplest form of neutralization reaction possible.
In the reality every acid and every base - no matter how strong - have some dissociation equilibria described by dissociation constant. In this particular case Ka for HCl is listed as 104 (which means it can be safely neglected) and dissociation constant Kb for NaOH is listed as 0.6 - which means sometimes it has to be taken into account.
sample size
Depending on the titrant concentration (0.2 M or 0.1 M), and assuming 50 mL burette, aliquot taken for titration should contain about 0.26-0.33 g (0.13-0.16 g) of hydrochloric acid (7-9 or 3.5-4.5 millimoles