CHEM 1312 Exam 4 Review

Gibb's free energy

100

What is true of delta G if a process at equilibrium?

Delta G = 0

200

What is true of the delta G of a spontaneous process?

delta G < 0

300

How do you calculate delta G from entropy and enthalpy?

delta G = delta H - T*delta S

400

How is delta G related to K and Q?

delta G = -RTlnK + RTlnQ

standard delta G = -RTlnK

500

Indicate the sign for delta H and delta S when a chemical reaction is spontaneous at low temperatures

delta H: negative

delta S: negative

Redox Rxns

100

What is the oxidation state of Zn in Zn(s)?

Zn(s) + ReO₄^-(aq) -> Re(s) + Zn²⁺(aq) (acidic)

What is 0?

200

What is the oxidation state of ReO₄^-?

Zn(s) + ReO₄^-(aq) -> Re(s) + Zn²⁺(aq) (acidic)

What is +7?

300

What is the oxidizing agent?

Zn(s) + ReO₄^-(aq) -> Re(s) + Zn²⁺(aq) (acidic)

What is ReO₄^- 

400

How many moles of e^- are involved in the redox reaction?

Zn(s) + ReO₄^-(aq) -> Re(s) + Zn²⁺(aq) (acidic)

What is 14?

500

How many moles of H⁺ are in the balanced redox reaction?

Zn(s) + ReO₄^-(aq) -> Re(s) + Zn²⁺(aq) (acidic)

What is 16?

Galvanic Cells

100

What is true about the E_cell of a galvanic cell?

E_cell > 0

200

Describe the path of electrons in an electrochemical cell

What is from anode -> wire -> cathode?

300

How are standard reduction potentials used to determine which species is reduced?

The reduction half-reaction with a larger (more positive/less negative) standard reduction potential occurs. The other species is oxidized. 

400

What happens to the size of the anode of the following galvanic cell as it is used?

Zn(s)|Zn²⁺(aq)||Ni²⁺(aq)|Ni(s)

What is decrease in mass?

500

What is the standard cell potential for the following reaction:

MnO₄^- (aq) + 8H⁺ + Fe²⁺(aq) -> Mn²⁺ (aq) + Fe³⁺ + 4H₂O (l)

What is 0.74V?

Thermodynamics of Electrochemical cells

100

Relate E_cell and delta G

delta G = -nFE_cell

200

What does it mean if a battery dies? (hint: what are E_cell and delta G)

The galvanic cell is at equilibrium (E_cell = delta G = 0)

300

What is E_cell in terms of E^o_cell and Q if the galvanic cell is not under standard conditions?

E_cell = E^o_cell - RTln(Q)/nF

400

A given galvanic cell has an E^o_cell = 0.51V. If n = 2, what is delta G?

delta G = -98.4 kJ

500

For a certain galvanic cell at 25^oC, E^o_cell = 0.15 but E_cell is measured to be 0.17. If n = 2, what is Q?

Q = 0.211

Electrolytic cells

100

What is true of the E_cell of electrolytic cells?

E_cell < 0

200

What reaction occurs at the anode?

oxidation

300

What is the charge of the cathode of an electrolytic cell?

negative

400

An electrolytic cell is set up for the electrolysis of Copper(II) iodide. What reaction occurs at the anode?

Cu²⁺(aq) + 2e^- -> Cu (s)

500

An electrolytic cell is set up for the electrolysis of molten copper (II) iodide. What are the products?

Cu(s) + I₂(s)