Question

Which of the following combinations would make a buffer with pH close to 3.0?
HClO₂   K_a = 1.1 × 10^-2
NH₃   K_b = 1.8 × 10^-5
HNO₂   K_a = 7.2 × 10^-4
C₅H₅N   K_b = 1.5 × 10^-9

Equal volumes of 0.10 M NH₄Cl and 0.10 M NH₃

Equal volumes of 0.10 M HClO₂ and 0.10 M NaClO₂

Equal volumes of 0.10 M HNO₂ and 0.10 M NaNO₂

Equal volumes of 0.10 M HCl and 0.10 M NaCl

Equal volumes of 0.10 M C₅H₅NHCl and 0.10 M C₅H₅N

Answer 1

Хоо, pkt = pka + log [base) Cacid] we want buffer with PA close to 3.0 . [base) = given Eaul volumes and Equal concentrations ob acid and bases. Let volume = x ii Cbase) Go B Cacid . Costom) G ł And, Log (1) 50 "PP - eka - ob acid 6 tom] (a) = 1

' la D) 1) Hclou 9 pka --Log C11x102) = 2.00 NH) K6 = 1.8x105, Kaiks = 1019 = Ka = 10th. Kas the = 5.6 x ola pką -Los Cs.6 xro') = 9.24 3) Have pka --Lay (712x167) = 3.1" 2 1 Fa- 10719 Tisycoa = 6.78166

pla= -log [ 6.7x226) = 5.2 And Hel and nach رأ won't o buffer solution. stoong acid A Hoog blaffer pH salt Ka=7-2x10h would make close to 3.0 i since pka = 3-1 :- Ans", HNO 2 ika=728104