A) So, B) Cao C) P4010 D) CO2 Free Response Questions 1. sulfurous acid, Hzsos,
ID: 519034 • Letter: A
Question
A) So, B) Cao C) P4010 D) CO2 Free Response Questions 1. sulfurous acid, Hzsos, is a diprotic acid Ki 17 x 10 3; 64 x 10 H a. Write an ionic equation for the aqueous ionization that corresponds to Kai. Write an ionic equation for the a ionization that corresponds to Kay Identify the conjugate acid base pairs in each of your two equations. b. Identify any amphoteric species, other than water in your equations. c. Assume the amphoteric species you identified in Partb is a base. Write an ionic equation for its aqueous ionization and calculate the corresponding Kb d. Is an aqueous solution of NaHso, acidic or basic? Explain your reasoning. e. Calculate the ph of a 0.50 M solution of Na2so3. Copyright 2015 Pearson Education, Inc. sasExplanation / Answer
1.
a)Ionic equation for the aqueous ionisation that corresponds to Ka1 is
H2SO3 (aq) <==> H+ (aq) + HSO3- (aq)
Ka1 = 1.7 x 10^-2 = [H+][HSO3-]/[H2SO3]
H2SO3 and HSO3- are conjugates
HSO3- (aq) <==> H+ (aq) + SO3-- (aq)..... Ka2 = 6.4 x 10^-8 = [H+][SO3--]/[HSO3]-
HSO3- and SO3-- are conjugates.
b). Amphoterics can behave both as an acid or a base. HSO3- ion is amphoteric because it can further dissociate its 2nd proton to form SO3-- (making it an acid), or accept a proton .
c). HSO3- (aq) + H2O <==> H2SO3 + OH- (aq),
Kb = Kw/Ka = 10^-14 / 1.7 x 10^-2 = 5.9 x 10^-13
d. It is acidic, because Ka of HSO3- is much larger than Kb of HSO3-.
e). [OH-] = [Kb*c].
Kb = 10^-14 / 6.4 x 10^-8 = 1.6 x 10^-7
[OH-] = [(1.6 x 10^-7)*(0.50)]
= 2.8x10^-4 M
pOH = -log(2.8x10^-4) = 3.6
pH = 14-pOH,
so pH = 1
2.
a.)The ability of an anion to act as a base can be determined by looking at the strength of the acid formed from it (its conjugate acid).
The anions of strong acids are weak bases that will not raise the pH significantly.
The anions of weak acids are relatively strong bases that will react with water to produce OH- ions, raising the pH.as we know that HCl and HBr are strong acids, so their conjugate base will be very weak .
CN- and NO2- are conjugate bases of weak acids HCN and HNO2 ,so they are strong.
NO2- (aq) + H2O(l) ---> OH-(aq) + HNO2(aq)
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