Chem Hw

HW Chapter 18 Name:

Show all your work in the space provided, and clearly indicate your final answer. No credit will be given for answers only. (For question 4, select the single correct response.)

1. A metal object is to be gold-plated by an electrolytic procedure using aqueous AuCl3 electrolyte. Calculate the

number of moles of gold deposited in 3.0 min by a constant current of 10.0 amperes.  [3 pts]

2. For the electrochemical cell, Cd(s) | Cd2+(aq) || Co2+(aq) | Co(s), determine the equilibrium constant (Keq) at

25C for the reaction that occurs.  [3 pts]

3. Calculate G (kJ/mol) for the following electrochemical cell: Cd(s) | Cd2+(aq) || Ni2+(aq)| Ni(s) [3 pts]

4. Calculate the cell emf for the following reaction at 25C: [3 pts]

Ni(s) + 2Cu2+(0.010 M) Ni2+(0.0010 M) + 2Cu+(1.0 M)

5. How long must a constant current of 40.0 A be passed through an electrolytic cell containing aqueous Zn2+

ions to produce 2.50 moles of zinc metal? [3 pts]

For questions 6-10, select the single correct answer. (4 x 1 pt)

6. Which one of the following reactions must be carried out in an electrolytic cell rather than in a galvanic cell? 

(1) Zn2+(aq) + Ca(s) Zn(s) + Ca2+(aq) (2) Al3+(aq) + 3Br–(aq) Al(s) + Br2( l)

(3) 2Al(s) + 3Fe2+(aq) 2Al3+(aq) + 3Fe(s) (4) H2(g) + I2(s) 2H+(aq) + 2I–(aq)

(5) Fe2+(aq) + Mg(s) Fe(s) + Mg2+(aq)

7. An electrochemical cell constructed from the following half cells, linked by a NaNO3 salt bridge. - a Ni electrode in 1.0 M NiCl2 solution - a Ag electrode in 1.0 M AgNO3 solution When the cell is running spontaneously, which statement is correct? 

 (1) The silver electrode loses mass and the silver electrode is the cathode. (2) The silver electrode gains mass and the silver electrode is the cathode. (3) The nickel electrode gains mass and the nickel electrode is the anode. (4) The nickel electrode loses mass and the nickel electrode is the cathode. (5) The nickel electrode gains mass and the nickel electrode is the cathode.

8. A galvanic cell has the overall reaction:

2Fe(NO3)2(aq) + Pb(NO3)2(aq) 2Fe(NO3)3(aq) + Pb(s)

Which is the half reaction occurring at the cathode? (1) NO3-(aq) + 4H+(aq) + 3e- NO(g) + 2H2O( l)

(2) NO3-(aq) + 2H+(aq) + e- NO2(g) + H2O( l) (3) Fe2+(aq) Fe3+(aq) + e-

(4) Pb2+(aq) + 2e- Pb(s) (5) Fe2+(aq) + e- Fe3+(aq)

9. In a galvanic cell, the half-reaction is (1) an oxidation half-reaction and occurs at the anode. (2) an

oxidation half-reaction and occurs at the cathode. (3) a reduction half-reaction and occurs at the anode.

(4) a reduction half-reaction involving electron transfer from the cathode to the anode

10. For a galvanic cell that uses the following two half-reactions,

3 Cu2+( aq) + 2 Ga( s) ⇌ 3 Cu( s) + 2 Ga3+( aq)

how many electrons are transferred? (1) 1 (2) 2 (3) 3 (4) 6