Buffer Solutions
What is a Buffer solution? What is the purpose of a buffer solution?
A Buffer is a solution of either a weak acid and its conjugate base, or a weak base and its conjugate acid. A buffer resists a change in pH.
What type of titration curve is this? (Draw on board)
Weak Acid Strong Base
20 mL of 0.50 M HCl is titrated with 0 mL of 0.30 M NaOH. What is the pH?
pH = 0.301
What is the molarity of Water?
55.5 M
Which of the following is a reduction reaction and an oxidation reaction
Cu2+ → Cu(s)
Ag(s) → Ag2+
Cu2+ → Cu(s) reduction
Ag(s) → Ag2+ Oxidation
What is the Henderson-Hasselbalch equation?
pH = pKa + log([base]/[acid])
20 mL of 0.50 M HCl is titrated with 10 mL of 0.30 M NaOH, what is pH at equil point?
pH = 7
20 mL of 0.50 M HCl is titrated with 10 mL of 0.30 M NaOH. What is the pH?
pH = 0.632
What is Ksp? What does Ksp tell us?
Ksp = solubility product constant, and allows you to predict when an ionic compound will precipitate out of solution.
What is the oxidation number of Chromium in (NH4)2Cr2O7
Cr = +6
What is the pH of a buffer solution containing [NH3] = 0.652 M and [NH4+] = 0.604. Ka = 1.15X10-10
pH = -log (1.15X10-10) + log (0.652/0.604)
pH = 9.97
20 mL of 0.30 M HF is titrated with 10 mL of 0.15 M KOH. Calculate the pH if the Ka of HF = 1.7X10-8
pH = 7.29
90 mL of 0.6 M of NH3 is titrated with 50 mL of 1 M HCl, what is the pH? Kb = 1.8X10-5
pH = 8.16
Calculate Ksp if a saturated solution of Zn(OH)2 contains 1.5 X 10-4 M Zn+2(aq) and 4.2X10-6 M OH-.
Ksp = [Zn+2] [OH-]2
Ksp = (1.5 X 10-4) (2(4.2X10-6))2
Ksp = 1.3 X 10-14
Write the reaction in standard cell notation:
Cu2+ → Cu(s)
Ag(s) → Ag1+
Cu/Cu2+//Ag+/Ag
What is pH of a buffer solution containing 0.150 M of HAc(aq) and 0.175 M of Ac-(aq). Ka = 1.8X10-5
pH = -log(1.8X10-5) + log(0.175/0.150)
pH = 4.81
20 mL of 0.30 M HF is titrated with 50 mL of 0.15 M KOH. Calculate the pH if the Ka of HF = 1.7X10-8
pH = 12.33
90 mL of 0.6 M of NH3 is titrated with 60 mL of 1 M HCl, what is the pH? Kb = 1.8X10-5
pH = 1.4
Ksp of Ca(OH)2 is 7.21 X 10-7. Calculate the molar solubility of the compound.
Ksp= [Ca2+] [OH-]2
Ksp= (x)(2x)2
Ksp = 0.00565 M
Balance the following redox reaction in acidic solution:
P + Cu2+ → Cu + H2PO4-
8H2O + 2P + 5Cu2+ → 2H2PO4- + 12H+ + 5Cu
Calculate the pH of a resulting solution when 20 mL of 0.80 M acid solution is added to a 100 mL buffer solution containing 0.30 M Acid and 0.50 M Base. Ka = 5.6X10-10
pH = 9.12
What is pH of titration at equivalence point if 20 mL of 0.30 M HF is titrated with 0.15 M KOH?
pH = 10.47
90 mL of 0.6 M of NH3 is titrated with of 1 M HCl, what is the pH at equivalence point? Kb = 1.8X10-5
pH = 4.84
Ksp of Ba3(PO4)2 is 2.81X10-6. Calculate the molar solubility if 0.30 M of Ba2+ is already in solution.
Ba3(PO4)2 = 3 Ba2+ + 2 PO43-
Molar solubility = 0.0051 M
Balance the following redox reaction in basic solution:
Pb2+ + IO3- → PbO2 + I2
8OH- + 5Pb2+ + 2IO3- → 5PbO2 +I2 + 4H2O