Question

A laboratory technician wants to determine the aspirin content of a headache pill by acid-base titration. Aspirin has a K_a of 3.0 x 10⁻⁴. If the pill is dissolved in water to give a solution about 0.0050 M, what is the pH of this solution? (Neglect dilution effects.)

If the solution in the problem above is then titrated against KOH solution, what will be the pH at the stoichiometric point.

Answer 1

HILINI Aspirin ( G Hq O4) ka= 3.0x104 And [ Aspinint = 0.0050 M Ja Aspisin Aspinios t tho Aspirin + Ho 0.0050 c ECO -a 0.0050-x LONCRETELLANERALE Kg = [ Asp I [hot] [ Aspinin neon s 3,08154 = 0.0050-1 0.0050-X STELLT = x 1.5 X 10 - 3.0x10x by solving quadratic equation n = 0.001083896 thot] =x=0.001083896 M Scanned with CamScanner

pH e-long Chy oog . - log (0.00108) pH = 2.965 pH = 2.96 prethe orphanagar solution Now abone solution is tibated against kom At stachiometric posits means the mole ratio i same it means it ń the post of Equivalency. Depioine + koy - Asp + tho since 0.0050M Aspirine will react with Asp will 0.0050m KoH fully form, which in turn water, with ILM will get dissociated in k = kwa 10x164 . 3.00154 K: 3.33 X 16-?) cs Scanned with CamScanner

Asp + ho Aspirin t the ton I 0.0050 IX E 0.005ox [ Aspirin ] [ our] [ AspJ 3.33x10 = (0,0050-x) we can sal neglect a since 3.33x10 3.33 X 107 X 0.0050 2 x 10 - 4. 082 X107 Tore J = 4.082 x167 M pOH = -log Core] = -log (4.082 8107) pOH = 6.389 pH a P4 - por pH = 14 - 6.389 = 7.61 IpH = 7.61 1 Scanngowith the answn in CamScanner

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