Electrochemistry problem

Electrochemical series application

1. Relative

1. Relative strength of oxidizing agents in terms of E▫ value

• L.H.S equation Called oxidizing agent.• E = measure the tendency. Forward direction.• Upper side E large +ve = effective e- accepter.• upper reaction is high oxidizing agent then

lower. Because E become more –ve.• F2 + 2e- → F2+ more oxidize and +. Up• Li+ + e- → Li more reduce and -.

2. Relative strength of reducing agents in terms of E value

• R.H.S equation Called redizing agent.• E = measure the tendency. Reverse direction.• Down side E large -ve = effective e- donor.• Down reaction is high redizing agent then

upper. Because E become more –ve.• F2 + 2e- → F2+ more oxidize and +. Up• Li+ + e- → Li more reduce and -.

3. Identifying the spontaneous direction of reaction

• Electrode potential show the redox reaction.• Ecell overall reaction can be calculate from E

value.• Ecell is + = spontaneous and Ecell is –ve = non

spontaneous.• Depend the oxidizing and reducing value.

Oxidizing agent oxidise any reducing agent the appear below.(anode E is +ve and E)

4. Calculation of Ecell

S.H.E

Reference electrode or primary electrode

• Attached either anode or cathode.• Oxidation or reduction = 0.• Standard condition.• H+/ H2(g,1atm) / pt.• Use to find other half cell electrode potential.• Example-• Zn(s) / Zn2+

(1M) // H+(1M) / H2(g, 1atm) / pt

Use to find half cell potential.

• Eocell = Eo

SHE - EoZn

• 0.763 = o - EoZn

• EoZn = - 0.763V

Difficulties setting SHE

• Pure and dry H2 gas.• Maintained 1atm pressure and ion.

Secondary electrode or calomel electrode

Also called mercury electrode

• KCl(sat) / Hg2Cl2(s) / Hg(l)

• Anode- 2Hg(l) + 2Cl-(sat) → Hg2Cl2(s) + 2e-

• Cathode- Hg2Cl2(s) + 2e- → 2Hg(l) + 2Cl-(sat

• Electrode potential depend upon concentration.

• Eocell = Eo

C – EoZn

Example

Advantage

• Easy to construct and transport.• Easy to handle.• No salt bridge.

Common type of cell

• Primary voltaic cell:- non rechargeable.• Secondary voltaic cell:- rechargeable.

Dry cell(leclanche cell)

Dry cell

Fuel cell

• Combustion produce energy.• H gas continuously bubbled through anode.• And oxygen at cathode.• Pt / H2(g) / OH-

(aq) / NaOH(aq) / OH-(aq) / O2(g) / pt

Cell potential-• Eo

cell = Eocathod - Eo

anode

• = 0.4 – (-0.83)• Eo

Zn = 1.23V,

Advantage

• Pollution free.• Electricity produce 70% then thermal power

station which produce 30%.• Do not discharge when the chemical are

consumed.

Disadvantage

• Less 1.32V because of reversible process.• Hydrogen is danger and costlyl.• Uses-• Automobile.• Space programmed for power.• Power generator.