CHEM 6C Final Review

Acid/Base

100

Name four strong acids.

HCl, HI, HBr, HClO₄, HNO₃, H₂SO₄

200

Order the acid/base definitions from most general to most specific.

Lewis, Bronsted-Lowry, Arrhenius

300

Calculate the pH of 6.50 x 10^-3 M KOH solution.

pOH = -log[OH-] = -log(6.50 x 10^-3) = 2.187
pH = 14.000 – pOH = 14.000 – 2.187 = 11.813

400

How does adding sodium acetate CH₃COONa affect the pH of a solution?

Increases pH (makes it more basic)

500

Titrate 25.0 mL of 0.100 M CH₃COOH with 0.100 M NaOH (at 25 °C). Ka(CH₃OOH) = 1.80 × 10–5. What is the pH after 30.0 mL NaOH is added?

CH₃COOH: .025L * .1M = .0025 mols

NaOH: .03L * 0.1M = .003 mols

After eq point

.055L total volume

.0005  mol base

[OH-] = mol base/ V = .0005 mol base/.055L = .0091 M

pH = 14 +log ([OH-]-[HA])

pH = 14 + log ([0.0091]) = 11.96 

Solubility

100

The Ksp expression for solubility of AgCl

Ksp = [Ag+][Cl-]

200

Which way does solubility equilibrium shift during formation of a complex ion. How does this affect molar solubility?

Shifts right, increases solubility

300

Determine whether PbF₂ would be more soluble in acidic solution

Yes, it contains a basic anion

400

Write the equation to calculate the solubility of PbCl₂ in pure water. Ksp PbCl₂ = 1.7 x 10^-5

Ksp = (s)(2s)² → s = 0.0162 M.

500

Write the equation to calculate the solubility of PbCl₂ in 0.25 M MgCl₂. Ksp PbCl₂ = 1.7 x 10^-5

Ksp = (s)(0.50 + 2s)2 →  6.80 E-5.

Electrochemistry

100

Compare a Galvanic cell and an electrolytic cell.

Galvanic cell - spontaneous. Electrolytic - not spontaneous

200

If a metal is ______ on the activity series, it is more likely to be oxidized.

Higher

300

How do you know which half reactions go in the anode/cathode?

Oxidation goes in the anode, reduction goes in the cathode

400

In a Galvanic cell containing copper and zinc, write and balance the two half reactions.

Zn (s) --> Zn2+ (aq) + 2e-

Cu 2+ (aq) + 2e- --> Cu (s)

500

Calculate the equilibrium constant for a Zn/Cu cell at standard conditions. Reduction of copper: 0.34 V. Reduction of Zinc: -0.76 V anode

Zn (s) → Zn2+ (aq) + 2e- 0.76

Cu2+ (aq) + 2e- → Cu (s) 0.34

Zn (s) + Cu2+ (aq) → Cu (s) + Zn2+ (aq) = 1.1 V 

E standard cell = 0.0592/n * logK

1.1  = 0.0592/2 * logK

1.45 x 1037 = K 

Kinetics

100

How do you find the reaction order from order of the reactants?

Sum the exponents of the reactants in the rate law.

200

What is the unit for k in a 2nd order reaction?

1/M*time

300

What is the integrated rate law for a 1st order reaction?

ln[A]_t = -kt + ln[A]₀

400

The activation energy of a reaction is 56.80 kJ/mol and the frequency factor is 1.5 x 10¹¹ /s. Calculate the rate constant at 25 Celsius.

K = Ae^-Ea/RT = (1.5E11) *e^{-56.8 kJ/mol*1000 J/kJ / 8.314J*298.15K} = 17/3

500

For the reaction 2NO (g) + O₂ (g) --> 2NO₂ (g) with rate = k[NO]²[O₂], explain why the following mechanism does not work.

1. 2NO (g) --> N₂O₂ (g) slow

2. N₂O₂ (g) + O₂ (g) --> 2NO₂ (g) fast

Rate law based on slow step is rate = k[NO]², which does not match experimental rate law.