Question

- O ACIDS AND BASES Predicting the qualitative acid-base properties of salts Consider the following data on some weak acids and weak bases: acid name hydrofluoric acid hypochlorous acid formula HF 6.8 x 104 HCIO 13.0x108|| base name formula 45 ammonia | NH3 | 1.8 x 10 - Pyridine CHN 1.7109 Use this data to rank the following solutions in order of increasing pH. In other words, select a 'l' next to the solution that will have the lowest pH, a '2' next to the solution that will have the next lowest pH, and so on. solution pH 0.1 M NaF 0.1 M NHACI 0.1 MKI choose one choose one choose one : choose one 5 ? 0.1 M KCIO |x

Answer 1

O. IM NaF-[c] HF + NaOH - NaF+ H₂O weak strong salt acid base Kaob HF = 6-8X10 4 pka = -logka = -log (68x101) = 3.17 pkW 214 For this salt pt foormula pH = + { pk wapka toge] = 1 [14+3:17+10g (0-1)] pH = 8.0850 O. IM NHAC =[c] HC ANH » NHA cl strongacid weakbase salt Nitz: kg = 1.8x105 pkb= -log kb = -log (1-8x105 ) = 4-745 for this salt pH = { pkw -plb _loge] pH = ± [14-4.745 10g (o.n] pH = 5.1275

salt olMKI ={1} HI et koll - KI tto strong acid strong base (neutral) so pH=7 Halo OlM kolo z{c] HClO + KOH KOH kolo t to weak acrd strong base salt Isabb Halo = 3x10-P pka_ -logka = -log (3x10 8) = 7.523 for this salt pit = = { pkw tpka loge] pH =+ 14+75-23 +10g (0-1] = 10-2015 O IM NH el < o IMKI <O IM Naf coolm kolo 15-1275) (7) (8.085) (10.2015)

pH: formula's for salt's weak acid & strong base salft ito pH = ± [pkw + pka + loge salf tlf o strong acidt weakbase pt = ₃ [ pk w plebe_loge