4.7Since the pKaof HCN is given as 9.1, its Ka5 1029.1. In more conventional notation, Ka583 10210. Hydrogen cyanide is a weak acid.4.8Hydrogen cyanide is a weak acid, but it is a stronger acid than water (pKa5 15.7). Since HCN is astronger acid than water, its conjugate base (CN2) is a weaker base than hydroxide (HO2), which isthe conjugate base of water.4.9An unshared electron pair on oxygen abstracts the proton from hydrogen chloride.4.10In any proton-transfer process, the position of equilibrium favors formation of the weaker acid andthe weaker base from the stronger acid and base. Alkyloxonium ions (ROH21) have approximatelythe same acidity as hydronium ion (H3O1,pKa521.7). Thus hydrogen chloride (pKaø27) is thestronger acid. tert-Butyl alcohol is the stronger base because it is the conjugate of the weaker acid(tert-butyloxonium ion).The equilibrium constant for proton transfer from hydrogen chloride to tert-butyl alcohol is muchgreater than 1.
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This note was uploaded on 09/20/2011 for the course CHM 2210 taught by Professor Reynolds during the Spring '01 term at University of Florida.