SS2: CHEMISTRY - 1ST TERM
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Periodicity and Periodic Table I | Week 15 Topics|1 Quiz
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Quantum Numbers Orbitals & Electrical Structure | Week 26 Topics|1 Quiz
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Periodicity and Periodic Table II | Week 312 Topics|1 Quiz
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Periodic Table and Atomic Properties
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Melting and Boiling Point
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Electrical and Thermal Conductivities
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Atomic Size [Radius]
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Ionic Size [Radius]
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Atomic Volume
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Ionization Energy
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Electron Affinity
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Electronegativity
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Differences between Ionization Energy and Electron Affinity
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Summary of Trends of Atomic Properties
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Theory Questions - Periodicity and Periodic Table II
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Periodic Table and Atomic Properties
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Periodicity and Periodic Properties III | Week 411 Topics|1 Quiz
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Periodicity and Periodic Properties IV | Week 55 Topics|1 Quiz
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Mass-Volume Relationship in Reaction | Week 68 Topics|1 Quiz
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Types of Reactions: Oxidation and Reduction | Week 7 & 87 Topics|1 Quiz
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Oxidation – Reduction Reaction II | Week 93 Topics|1 Quiz
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Electrode Potential and Electrochemical Cells I | Week 106 Topics|1 Quiz
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Electrode Potential and Electrochemical Cells II | Week 115 Topics|1 Quiz
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Electrolysis I | Week 128 Topics|1 Quiz
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Electrolysis II | Week 138 Topics|1 Quiz
Measuring Standard Electrode Potential
Topic Content:
- Measuring Standard ElectrodeElectrodes are conductors, in the form of wires, rods or plates, through which current enters and leaves the electrolyte. When the current leaves the electrodes it is known as the cathode... More Potential
- Standard Electrode Potential of Copper Half-cell
- Standard Electrode Potential of Zinc Half-cell
To measure the standard electrode potential of metal ions, its electrode is connected to a standard hydrogen electrode via a salt bridge and a voltameter to show the readings. A salt bridge is an inverted U-tube containing a saturated solution of KNO3 or KCl, its function is that it allows the migration of ions between two electrodes.
Electrode potentials are measured under the following standard conditions:
(i) concentration of the electrolyteAn electrolyte is a substance that dissociates in water into charged particles called ions. Positively charged ions are called cations. Negatively charged ions are called anions. Simply, an electrolyte is a... More in 1.0 mol dm-3
(ii) gaseous reactant at one atmospheric pressure
(iii) temperature of the cell at 25°C or 298K
Under these conditions, the electrode potential is called standard electrode potential Eo. The superscript (o) stands for the standard state.
Standard Electrode Potential of Copper Half-cell:
When the Cu2(aq)/Cu(s)half-cell is connected to the 2H+(aq)/H2(g) half-cell by a salt bridge the voltameter reads 0.34 Volts. This is the potential difference between the two half cells and it is known as the electromotive force (e.m.f) of the cell.
The half-cell reaction at the copper and hydrogen electrode shows that electrons flow from the hydrogen electrode to the copper electrode.
Reactions at the Electrodes:
At hydrogen electrode:
H2(g) → 2H(aq) + 2e– (Oxidation)
At Copper electrode:
Cu2+(aq) + 2e– → Cu(s) (Reduction)
Overall reaction:
Cu2+(aq) + H2(g) → Cu(s) + 2H+(aq)
The positive sign in e.m.f of copper shows that copper ions Cu2+ has a greater attraction for electrons than H+
Cu2+(aq) / Cu(s) : Eo = + 0.34 volts
Standard Electrode Potential of Zinc Half-cell:
When Zn(s)/Zn(aq) half-cell is connected to the 2H+(aq) /H2(g) half-cell by a salt bridge, the voltameter reads – 0.76 Volts, but with the zinc electrode forming the negative terminal relative to the standard hydrogen electrode.
The half-cell reaction at the zinc and hydrogen electrode shows that electrons flow from the zinc electrode to the hydrogen electrode. Oxidation takes place at the zinc electrode and reduction at the hydrogen electrode.
Reactions at the Electrodes:
At the zinc electrode:
Zn(s) → Zn2+(aq) + 2e– (Oxidation)
At the hydrogen electrode:
2H+(aq) + 2e → H2(g) (Reduction)
Overall Reaction
Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g)
The negative sign in e.m.f of zinc shows zinc has the potential of losing electrons to hydrogen ions or hydrogen ions have a greater attraction for electrons than Zn2+
Zn2+(aq) / Zn(s), Eo = -0.76 Volts