Chem 123-CXB 206 t, wwU. CHEN/XVai Titration of a C×\' (1913 rning.com/ibiscms/m

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Chem 123-CXB 206 t, wwU. CHEN/XVai Titration of a C×' (1913 rning.com/ibiscms/mod/ibis/view.php?id 2427462 3 of 4 Map ths question was witen by Brandon Dietrich at Western Washington University You are titrating 50.00 mL of a 0.100 M HCIO2 (chlorous acid) solution with 0.100 MNaOH. The pk, of HCIO2 is 1.96. HCIO, aoH (aq CIO, ag+ H,o Once you have added 8.00 mL of NaOH solution: 1) What major species are still present in solution? (mark all that apply) 2) What is the pH of the solution? neutral O acidic O basic HCIO2 OH Only mark species that will be present after the titration reaction has finished, but before taking into account any small amounts formed at equilibrium or from the auto-ionization of water 3) Assuming you have already taken into account any dilutions from the titration, what method would you use to solve for the actual pH? O Use an ICE table and the Kb O Use an ICE table and the K O Use the excess OH, to calculate the pH O Use the Henderson-Hasselbalch equation U Previous O Next Save And Ex

Explanation / Answer

we know that

moles = molarity x volume (L)

so

moles of HCl02 taken = 0.1 x 50 x 10-3 = 5 x 10-3

moles of NaOH added = 0.1 x 8 x 10-3 = 0.8 x 10-3

HCl02 + OH- ---> Cl02- + H20

moles of HCl02 reacted = moles of NaOH added = 0.8 x 10-3

moles of Cl02- formed = moles of NaoH added = 0.8 x 10-3

moles of HCl02 left = 5 x 10-3 - 0.8 x 10-3 = 4.2 x 10-3

all the OH- is consumed

So

the major species are HCl02 and Cl02-

now

the major species is still HCl02 and acid

so

the solution is acidic

now

HCl02 and Cl02- form a buffer

for buffers

pH = pKa + log [ base / acid]

so

use the henderson hasselbach equation

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