sheet 3 electrochemistry
DESCRIPTION
electochemistryTRANSCRIPT
1
SHEET 3
1- Consider a galvanic cell based on the reaction
Al+++(aq) + Mg(s) → Al(s) + Mg++(aq)
v37.2-=E
v66.1-=E
Mg++Mg
A l+++A l
→
→
Give the balanced cell reaction and calculate E° for the cell.
2- Describe completely the following galvanic cell based on the following half
reactions.
Cl2 + 2e- → 2 Cl- E°=1.36 v
Br2 + 2e- → 2 Br- E°= 1.09 v
3- Predict whether the following reaction would proceed spontaneously as
written at 298 K.
Co(s) + Fe++ (aq) → Co++(aq) + Fe(s)
Given that [Co++]=0.15 M and [Fe++]=0.68 M
v44.0-=E
v28.0-=E
Fe++Fe
C o++C o
→
→
4- Calculate the EMF for the cell based on the following half reactions
VO2 + 2 H+ + e- → VO++ + H2O E° = 1.00 v
Zn++ + 2 e- → Zn E° = -0.76 v
Where: T=25°C [VO2++]=2.0M
[H+]=0.5M [VO++]=1.0x10-2M
[Zn++]=1.0x10-1M
5- Consider the cell described below:
Zn|Zn++(1.00M) || Cu++(1.00 M)|Cu
2
Calculate the cell potential after the reaction has operated long enough for
the [Zn++] to have changed by 0.2 mol/L. (Assume T=25°C)
6- Calculate EMF of the following cell if v-0.76=EZn→++Zn
Zn(s)|Zn++(aq,0.1M)||Zn++(aq,1.0M)|Zn(s)
7- Calculate the [Cu++]/[Zn++] ratio at which the following reaction will
become spontaneous at 25°C.
Cu(s) + Zn++(aq) → Cu++(aq) + Zn(s)
8- Consider the following half reactions
MnO4-(aq) + 8 H+(aq) + 5e- → Mn++(aq) + 4 H2O (L) E°=1.51
NO3-(aq) + 4 H+(aq) + 3 e- → NO(g) + 2 H2O (L) E°=0.96
Predict whether NO3- ions will oxidize Mn2+ to MnO4
- under standard state
conditions.
9- How long will it take to plate out 1.0 kg Al from aq Al+++ with a current of
100.0 A? (M.wt. of Al=26.98).
10- What mass of Co from aq Co++ can be produced in 1.0 h with a current of
15 A? (M.wt. of Co= 59).
11-An unknown metal M is electrolyzed. It took 74.1 s for a current of 2.00 A
to plate out 0.107 g of the metal from a solution containing M(NO3)3.
Identify the metal.