iodic Table tion 18 of 25 Incorrect A Sapling Learning Calculate the volume, in

Question

iodic Table tion 18 of 25 Incorrect A Sapling Learning Calculate the volume, in liters, of 1.565 M KoH that must be added to a 0.112 L solution containing 9.86 g of glutamic acid hydrochloride (H3Glu CI Mw 183.59 g/mo) to achieve a pH of 10.26. Glutamic acid (Glu) is an amino acid with pKa values of pKa1 2.23, pKaz 4.42, pKa 995 Number 0.023 CH-CH2-CH2 Incorrect. Your answer only accounts for the amount of KOH required to convert a portion of the HGlu to G t does not include the amount of KOH that was required to convert the initial H3Glu n solution to HGlu Glutamic Acid Hydrochloride Remember to add the number of moles of KoH required to convert H3Glu* to H2Glu, and then to HGlu to the number of moles required to convert a portion of the HGlu to Glu2 before calculating the volume.

Explanation / Answer

the pH is nearest to the pKa3 value, meaning that we MUST use plenty of KOH in order to "protonate" pKa1, pKa2 and pKa3

so....

pH = 10.26 (target)

moles of Glu = mass/mol = 9.86/183.59 = 0.0537 mol

volume of KOH that will require to neutralize the protons:

0.0537 mol of Glu = 2*0.0537 mol of KOH

so

0.0537 *2 = 0.1074 mol of KOH

For volume

M = mol/V

V = mol/M = (0.1074)/(1.565) = 0.0686 Liters

now,

moles of HGlu-2 formed in neutraliztion-- > !:1 ratio with GluHCl = 0.0537

now...

x + y = 0.0537

where x = moles of KOH, y = moles of HGlu-2

the henderson hasselbach equation

use pKA3 since it is the nearest value for pH:

pH= pKa3 + log([Conjugate]/[acid])

substitute known data

10.26 = 9.95+log(x/y)

solve for x/y ratio

x/y = 10^(10.26-9.95) = 2.0417

so

x = 2.0417y

substitute this equation in

x + y = 0.0537

2.0417y+ y = 0.0537

3.0417y = 0.0537

y = 0.0537 /3.0417 = 0.01765

so

x + y = 0.0537

x = 0.0537 -0.01765 = 0.03605

so..

voluem of KOH for this 0.03605 moles:

V = 0.03605 / 1.565 M = 0.023 Liters

so

total Volume = V1+V2 = 0.023+0.0686 = 0.0916 L

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