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1. بسم الله الرحمن الرحيم | Nature, Beautiful nature, Landscape.
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By; Abobakr Abdel Wahab. 2. Welcome 2 nd Lecture.
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3. Primary reference electrode. Reference SHE SCE Ag o / AgCl.
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4. I. The reference electrode: The reference electrode: Is a half cell with known electrode potential and its potential does not change during potentiometric measurement. It is left hand electrode by convention..
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5. . Desired Characteristics: K nown or fixed potential, E ref C onstant response (even when there is a net current in the cell ) I nsensitive to composition of solution under study O beys Nernst Equation R eversible R ugged and easy to assemble.
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6. Common Reference Electrodes used in Potentiometry 1. Primary reference electrode A. Standard hydrogen electrode (SHE) or (NHE) 2 . Secondary reference electrode Saturated Calomel Electrodes (SCE) (Hg in contact with Hg 2 Cl 2 & KCl sat ) Silver/Silver Chloride Electrode.
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Chapter 19.2: Standard Potentials - Chemistry LibreTexts.
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2H + + 2 e - ↔ H 2 (g). 8. . Nernst equation. .
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10. لا يتوفر وصف.. 2. Saturated Calomel Electrodes (Hg in contact with Hg 2 Cl 2 & KCl ).
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11. I. Composition: ( M") In contactwith its sparinglywatersolublesalt, in solution of saturated common ion Metal/sparingly soluble salt/süurated anion ) N.B: saturated 2. Example: SCE: 3. Half cell reaction: Hg2Clze 2Hg++ 2e- 2Hg0 (s) Hg2C12 + +2Cl¯(aq).
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12. . .
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13. Advantages: 1. Easily prepared 2. Equilibriation due to temperature change is slow Dissadvantages : leakage of KCl into sample, mercury contamination.
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14. 3. Silver/Silver Chloride Electrode. most widely used reference electrode system Ag electrode immersed in KCl solution saturated with AgCl ( aq ).
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15. I. Composiåon: (MO) In conuctwith its sparinglywaer soluble salt, in solution of common ion ( soluble salt/saturatEd anion ) 2. Example: Ag/AgCl/ KCI (sat) N.B: saturated 3. Half cell reacüon: AgCl Ag++ Cl-.
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16. .
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17. Advantage : Less toxic 2. Thermal stability can be used at temperatures > 60 o C Disadvantage : d ifficult to prepare AgCl has lare solubility in saturated KCl plugging of the junction between electrode (Ag) and analyte soln..
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18. Cute Chemistry Thank You Stickers Zazzle com.