slide revisi principles of electrolysis in aqueous solution

8/7/2019 Slide Revisi Principles of Electrolysis in Aqueous Solution

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Principles of Electrolysis in

Aqueous Solution

Nurhasanudin

3334081633

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19 April 2011


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Outline

1. Preface

2. Electrochemistry of Aqueous Solution

3. The Possibilities of Reaction in Anode and Cathode

4. Predicting The Product of Electrolysis in Aqueous

Solution

5. Hydrogen Evolution During Electrolysis in Aqueous

Solution

6. Anodic and Cathodic Reaction During Electrowinning

and Electrorefining in Aqueous Solution7. Refference

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3

Electrolysis

Aqueous

Solution

Fused Salt


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Type of Aqueous Solition Electrolyte

AcidBasic

Salt

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Example NaCl

Fused salt

When heat NaCl till it

melts temperatur, then

we will get molten Nacl,is called fused salt of

sodium chloride

NaCl Na+ + Cl-

Aqueous solution

Whereas if NaCl is

dissolved in water, gives

the aqueous solution ofsodium chloride

NaCl Na+ + Cl-

H2O H+ + OH-

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Electrochemistry of Aqueous Solution

The total electromotive force of a cell may be regarded as

consisting of a cathodid and an anodic potential. Thus for a cell :

X/X-, A+/A

The two half cell corespond to the reaction :

A+ + e- = A and X- = X + e-

The first of these may be called reduction the second an

oxidation

The total emf as different between two reduction potential

E = EA+/A - EX/X-

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The half cell potential may again be expressed in term of

standard half-cell potential in the electrolyte

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Possibilities of reaction in anode and

cathode

Anode4OH- 2H2O + O2 + 4e

-

X- X + e-

here there is choice of hydroxide orother negative ion will be discharge

to anode

Cathode

2H+ + 2e- H2

A+ + e- A

here each two hydrogen ion cangains two electron and become

hydrogen atom, also occur to theother positif ion but only one will

be selected

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PredictingThe Product of Electrolysis

in Aqueous Solution

There is three factor to be discharged

1. Reactivity series2. Concentration of solution

3. The kind of electrode used

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Hydrogen Evolution During Electrolysis of

Aqueous Solution

Hydrogen ions are always present in aqueous electrolyte

And lowering the current efficiency at the cathode

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The following need to know about hydrogen evolution

1. The equilibrium single electrode potential of the metal and

hydrogen2. The -i relationship for the discharge of metal as well as

hydrogen at the cathode

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The Polarisation curve

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Tabel of Reduction Potentials

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Anodic and Chatodic Reaction During Electrowinning

And Electrorefining in Aqueous Solution

In aqueous solution electrolysis the anode is generally made

of an inert lead based alloy (usually Pb, Sb, As). The anodic

reaction in acidic and alkaline aqueous solution may be

written as follows.

Acidic solution 2H2O = O2 + 4H+ + e- , Eo = - 1,23

Alkaline solution 4OH- =2H2O + O2 + 4e-, Eo =-0,40V

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Revisi : the reaction in cathode during electrosysis that couse thesolution around the cathode become more alkaline

Cathodic reaction

2H+ + 2e- H2

in the cathodic raction, the hydrogen ion migrate toward the cathode and combine

with electron and form the hydrogen gas, and since the water disociated into ion

hydrogen and hydroxide, and at the cathode the hydrogen ion combine withelectron and leave the hydroxide behind, hence the solution around cathode

became alkaline.


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REFFERENCES

Rosenqvist. Principles of Extractive Metallury, McGraw Hill Kogakusha Ltd.,

Tokyo, 2nd ed., 1983.

Ray&Ghosh. Principles of Extractive Metallury,

2nd ed.1991

http://myadvocator.com/chemistry/quick-revision-series/electrolysis-of-aqueous-

solution/

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slide revisi principles of electrolysis in aqueous solution

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