محاضرات في الكيمياء الكهربية

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بسم الله الرحمن الرحيم

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السلام عليكم ورحمة الله وبركاتة

في هدا الموضوع راح انزل لكم دروس في الكيمياء الكهربية

اتمنى انها تفيدكم يارب

وبسم الله نبدا


Electrochemistry -Electrode DynamicChem.


Electrochemical cells

Electrochemistry studies the change of electrical energy to chemical energy through electrolytic cells.
And also, change chemical energy to electrical energy through galvanic cells (voltaic cells or Daniel cells)
Therefore, we have two electrochemical cells
1- Electrolytic cells 2- Galvanic cells.



1- Electrolytic cells


Due to current is passing in conduct electrolyte →cause chemical change (i.e oxidation-reduction reaction, oxidation at the anode and reduction at the cathode.
So, this cell is called electrolysis cells
e.g:1- electrolysis of مصهورNaCl between two passive electrodes
2- Electrolysis of NaSO4 solution between passive electrodes.


3- Electrolysis of NaCl solution between passive electrodes.
4- Electrolysis of CuSO4 solution between passive electrodes.
5- Electrolysis of CuCl2 solution between passive electrodes.
6- Electrolysis of CuSO4 solution between cupper electrodes.
7- Stichiometry of electrolysis 8- Faraday law’s
Presentation on the applications of electrolytic and galvanic cells

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2- Galvanic cells


Change the chemical energy to electrical energy through physical or chemical change
The electromotive force “emf” of the galvanic cell produce due to the big difference in potential.
i.e decrease in free energy (∆G=-ve)
i.e Spontaneous process


Types of galvanic cells


1- Chemical cells

Here electrical energy produce due to occur chemical change
a- chemical cells with transfer
b- chemical cells without transfer
2- Concentration cells
Here electrical energy produce due to occur physical change accompany by transfer of mater from place to another


Concentration cells divided into:



i- Electrode concentration cells
a- Gaseous concentration cells
b- Amalgam concentration cells
ii- Electrolytic concentration cells
a- Electrolytic conc. Cells with transfer
b- Electrolytic conc. Cells without transfer

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What is the electrode reactions?

The reactions that occur due to the transfer of electrons to or from the electrode
In galvanic cells, the oxidation process occur at the anode and take – ve sign
While the reduction process occur at the cathode and take + ve sign
This is the reverse of electrolytic cell
The electrode can write by its name M/Mc+n


Notes:

If emf +ve sign means spon. Process, ∆G= -ve


If emf -ve sign means non-spon. Process, ∆G = +ve
Since, emf = L + R
Measurements of E0, for pure metals- P 1 atm- activity of solution =1
– express the potential of electrodes by reduction potential (ما لم ينص غي غير ذلك)
e.g: E0 = - 0.76 v for Zn
That is mean that E0 (Zn+2/Zn) = - 0.76 v



Applications of electrochemistry:

1- Electrochemical batteries
2- Fuel cells
3- Metal finishing
4- Refining and production of metal
5- Metals and material processing
6- Corrosion control
7- Electrolysis
8- Determination of physical parameters.
E.g. K, equilibrium constant, E0 stander cell potential, PH , reaction rates and …..
9- Titration (coductomertric, potentiometric)
10- Recycling of industrial process

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Reversible and irreversible cells


1- Reversible cells

When the cell says reversible cell?
1- if emf of the cell equal the potential of external power supply (battery)
2- if potential of external power supply › emf of the cell → current pass in the reverse direction , that is mean that the chemical reaction inside the cell pass in the reverse direction.
Cu + Zn+2 → Cu+2 + Zn

1- Reversible cells

When the cell says reversible cell?
1- if emf of the cell equal the potential of external power supply (battery)
2- if potential of external power supply › emf of the cell → current pass in the reverse direction , that is mean that the chemical reaction inside the cell pass in the reverse direction.
Cu + Zn+2 → Cu+2 + Zn


3- if the potential of the external battery < emf of the cell → low current pass according to the chemical reaction occur inside the cell.
i.e. Zn + Cu+2 → Zn+2 + Cu
So, the cell which have ( (تتوفر لهاthree conditions called reversible cell.
e.g: Danial cell ((عرض الخلية
Zn /ZnSO4 // CuSO4 / Cu

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وهاذي صورة الخلية الجلفانية

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وهذي صورة توضح الفرق بين الخلية الجلفانية والالكتروليتة

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Nernest Theory [ Electrode potential theory]


Before we speak about the postulates of the theory, first we must know the factors affecting on the electrode potential:
1- The metal solution pressure (SP)
2- Osmotic pressure of solution (OP), i.e concentration of solution around the electrode.
Osmosis: It is the flow of solvent molecules from pure solvent to the solution through semi permeable membrane separate between them.
Osmotic pressure π: It is the pressure required to be applied on the solution to prevent the flow of solvent molecules to the solution.
3- Temperatures 4- Valence of metal ions.


لو القضيب سالب بالتالي تحيط به الالكترونات

i.e ability of the metal to loss electrons >ability of metal ion to deposit
i.e Ox process is occur
Here, potential difference i.e. there are electrode potential

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i.e ability of metal ion to gain electrons then change to metal deposit >ability of metal to dissolve
i.e red process occur
·˙· metal become +ve charged Here, potential difference i.e. there are electrode potential

هذا في حالة القضيب الموجب


In this case no charge is formed i.e no edl is formed
·˙· no potential difference,
i.e. there is no electrode potential

وهذا في حاله القضيب او القطب المتعادل بدون اي شحنات

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