Steve’s Lava Chemistry Review

Buffer Solutions

100

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.

200

What is the Henderson-Hasselbalch equation?

pH = pKa + log([base]/[acid])

300

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

400

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

500

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

Titrations

100

What type of titration curve is this? (Draw on board)

Weak Acid Strong Base

200

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

300

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

400

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

500

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

Titrations 2

100

20 mL of 0.50 M HCl is titrated with 0 mL of 0.30 M NaOH. What is the pH?

pH = 0.301

200

20 mL of 0.50 M HCl is titrated with 10 mL of 0.30 M NaOH. What is the pH?

pH = 0.632

300

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

400

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

500

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

Solubility

100

What is the molarity of Water?

55.5 M

200

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.

300

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

400

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

500

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 PO₄^3- 

Molar solubility = 0.0051 M

Electrochemistry

100

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

200

What is the oxidation number of Chromium in (NH₄)₂Cr₂O₇

Cr = +6

300

Write the reaction in standard cell notation:

Cu²⁺ → Cu(s)

Ag(s) → Ag¹⁺

Cu/Cu²⁺//Ag⁺/Ag

400

Balance the following redox reaction in acidic solution:

P + Cu²⁺ → Cu + H₂PO₄^- 

8H₂O + 2P + 5Cu²⁺ → 2H₂PO₄^- + 12H⁺ + 5Cu

500

Balance the following redox reaction in basic solution:

Pb²⁺ + IO₃^- → PbO₂ + I₂ 

8OH^- + 5Pb²⁺ + 2IO₃^- → 5PbO₂ +I₂ + 4H₂O