Question

5) The second pK, value for any diprotic or triprotic acid (like H:CO3 or H;SO4) is always higher than the first pKa. Which of the CARDINal rules is responsible for this? Justify your answer in a sentence or two. 6 The acid triflic acid (shown at right) is one of the strongest known acids with a pKg of about -15. Compare its features to that of sulfuric acid and explain which of the CARDINal rules gives it its exceptional strength (more than one may apply, so be complete). OH 7) Methanethiol (CHSH) has a pK, value of 10.4 and methanol (CH,OH) has a pK, value of 15.5. Why does methanethiol have a lower pK,? If these two compounds were reacted, which would be expected to protonate the other? What is the difference in acidity between the two (104pka)2

Answer 1

he second pka valute for any dipotic or triptotic Question ) The second pks valle acich HB CO OT HQSOW) is always higher tha pka. Reason: Poly protic auck can lose y porc aude can lose two or more audic protons Whos os, diprotfc audu and typrotfc acids cole spe types of acids that can lose two and three protons, respectively pka, = large Cags. 45ou cag) Diprotic acid (Hg501) an H-0---H Masou cag) + + 480u cag) . Hou caq) = #ta + soi caq) pka, = rsmall Bocaue to delocalization The first discouatton constant Te necessostly greater than the second ce pka, soka), this is because the first. Ouate in alucys the most strongly audio, followed in order by the next most strongly Guar Two onions po stablize Therefore, the first pka step 06 HASO will occur completely. the structor which why Mason PA considered to be a strong aud, the gapka diono atton step is only weakly dissociating. Question to the and trittic and is the one of the strongest auds ooith a pka % about v15. fotot noi Hoy F_C_S_OH OH Cotton Cito fortable che HaSO4caq) 4 + H50 W -o-sto caq Confugare base stabilized by the resonance, that is why shoes ox CF350 ₂4 con t a + CF3303 conjugate base * The higher the dectronegativity, the greates the attraction So, tri Hic and contain F*C-s ? F-atom which also affect F :0: es pka Vole. anion is stabilized by resonance and - I nductive effect) 11

That is why, triflic and qualifies as a superand. Both aud and its conjugate horse CFg So, known as triflote, resist oxidat Pon /reduction reactions. Question : 7 Methane thiol has a pka = 10L Methanol has apka = 15.5 Why? Reason* The lower pa ** The lower pka Value 6 10.4 for me thanthiol indicates thal ud a stronger and than methanol with a pka value 06 15.5. The forget abomic size of sufwr compoured to oxygen results in lower clectron density and a more stablo conjugate base. So, methane theol . protonated faster than methanol, because of the size of oxygen and sulfur The size of oxygen smaller than switcoin due to this the attraction between oxygen and Hydrogen pohigh, whereas Swful and hydrogen held by the weal attraction, so it can easily donate the poton. 0-4 Strong S-H weak * Thestefore, CHISH more stronger strong acid) than CH3OH.