Take the quiz after reviewing the notes on Electrochemistry
- When a chemical reaction can produce an electric current we have an electrochemical cell
- The galvanic cell is an example of an electrochemical cell. Zn is the anode and Cu is the cathode.
- The chemical reaction in an electrochemical cell is spontaneous reaction or ΔG < 0 or negative
- The electrode at which oxidation takes place is called the anode
- The electrode at which reduction takes place is called cathode
- In an electrochemical cell the anode is at a negative potential (Increased negative charge due to accumulation of electrons M → Mn+ + ne-¹)
- The anode and the cathode can be determined from the standard electrode potential values for he electrode
- When comparing the values a larger value for the standard reduction potential indicates that this electrode would undergo reduction in comparison to the electrode having a lower standard reduction potential
- You can calculate the E°cell value for the cell E°cell = E°cathode – E°anode
- If the cell emf obtained is positive the choice of electrodes are right which also implies the reaction is spontaneous ΔG = -ve
- If the value is negative it represents a non spontaneous reaction, this reaction will not occur or ΔG = +ve or greater than zero.
What is the role of a salt bridge in an electrochemical cell
- The salt bridge helps in maintaining the electrical neutrality of the solutions in the anodic and cathodic compartments
- The salt bridge helps in completing the cell circuit
- A simple form of the salt bridge is a filter paper soaked in KCl
- The electrolyte should preferably contain a salt of a strong acid and a strong base – the salt should not undergo hydrolysis
- A glass tube bend twice at 90° or a U shaped glass tube can be used
- It should be filled with a warm solution of agar in water and KNO3.
- The contraption should be allowed to cool and you will have a gel in the glass tube which will serve as a source of positive and negative ions
- Such salt bridges have a life span, once all the ions have been used up they should be replaced
- In a Daniel cell, what form does the salt bridge take?
- Can you regenerate an electrochemical cell?
- Is the galvinic cell a primary or secondary cell?
- How can you vary the emf of an electrochemical cell?
- What is the effect of temperature on an electrochemical cell?
Electrochemical cells, redox reactions, anode, cathode, positive, negative, oxidation, reduction