##### Exam 3B Spring 2004

March 26, 2004

Possibly useful information:

 pH = –log[ H3O+ ] pOH = –log[ OH– ] pH + pOH = 14.00 at 25 oC Kc = KaKb/Kw KaKb = Kw (for a conjugate acid/base pair) log(1.0×10–3) = –3 log(1.0×10–4) = –4 log(2.0×10–3) = –2.698970004 log(2.0×10–4) = –3.696870004 log(3.0×10–3) = –2.522878745 log(3.0×10–4) = –3.522878745 log(4.0×10–3) = –2.397940009 log(4.0×10–4) = –3.397940009 log(5.0×10–3) = –2.301029996 log(5.0×10–4) = –3.301029996 log(6.0×10–3) = –2.22184875 log(6.0×10–4) = –3.22184875 log(7.0×10–3) = –2.15490196 log(7.0×10–4) = –3.15490196 log(8.0×10–3) = –2.096910013 log(8.0×10–4) = –3.096910013 log(9.0×10–3) = –2.045757491 log(9.0×10–4) = –3.045757491 Acid Ka (25 oC) pKa HClO 2.9×10–8 7.54 HCN 6.2×10–10 9.21 H3AsO4 6.0×10–3 2.22 H2AsO4– 1.0×10–7 7.00 HAsO42– 3.2×10–12 11.49 HOCN 3.5×10–4 3.46 Salt Ksp (25 oC) BaF2 1.0×10–6 CaSO4 9.1×10–6 Pb(OH)2 1.2×10–15

1. Complete and balance the following reactions:

a. H2SO4(aq) + CsOH(aq)

b. CH3CH2NH2(aq) + H2O(l)

c. H3AsO4(aq) + H2O(l)

d. Cu(NO3)2(aq) + Li2S(aq)

e. HClO(aq) + CN(aq)

f. Mn2+(aq) + H2O(l)

g. Ni(ClO4)2(aq) + NaOH(aq)

2. For each of the following salts, indicate if an aqueous solution will be acidic, basic, or neutral. If the salt is not neutral, write the reaction that determines the acidity or basicity.

a. KBr

b. Fe(ClO4)3

c. Na2CrO4

3. A solution is made that is 1.0 mM NaH2AsO4 and 1.0 mM Na2HAsO4 at 25 oC.

a. Estimate the pH of the solution.

b. Estimate the pH of the solution after 0.010 mmol of NaOH is added to 1.0 L of the solution.

c. Estimate the pH of the solution after 0.10 mol of NaOH is added to 1.0 L of the solution.

4. Estimate the molar solubility of lead hydroxide in pure water at 25 oC.