Galvanic cells

Galvanic cell

is a type of electrochemial cell in which chemical energy is converted into electrical cells

An electrochemical cell

An electrochemical cell is a device in which chemical energy is converted into electrical energy or vice versa.

Battery

a combination of galvanic cells connected in a series

Purpose of the two half cells

The two half cell seperate oxidation and reduction, thus prevent contact between reactants, allowing electrons to be forced to travel through the external circuit connecting the two half cells, allowing the chemical energy to be converted into electrical energy

Electrodes

Electron conducting rods where oxidation/reduction occur allowing current to flow

Electrolytes

a non reactive solution that enables the flow of ions and help maintain electrical neutrality and complete the internal circuit

Salt bridge

Salt bridge connect the two electrolytes of the two separated half cells where It completes the cell’s electrical circuit by allowing the flow of ions, thus maintaining electrical neutrality.

• This prevents the accumulation of charge in cells by providing cations that move towards the cathode and anions that move towards the anode.

Salt bridge is an electrical connection between the two half cells in a galvanic cells where it is usually made from a material satured in electrolyte solutions.

In order for a salt solution to be suitable for use in a salt bridge, it must be very soluble in water, unreactive and will not form an insoluble compound (precipitate with half cells)

• Will be spectator ions

• Most common salt brdige is KNO3

External circuit

Refers to the wire that connects the two electrode together allowing electron to flow from anode to cathode, allowing chemical energy to be converted into electrical energy.

Anode

The site of oxidation

• Substance at the anode is the reductant and produces electrons through the external circuit

• Electrons flow from here

• Has negative charge in the galvanic cells

Cathode

The site of reduction

• Substance at the cathode is the oxidant and receives the electrons through the external cirucit

• Electrons flow to here

• Have a positive charge in the galvanic cell.

Explain the significance of the increase in temperature of the solution

Not all of the chemical energy is transformed into electrical energy. Some of the chemical energy stored in the reactants is released as heat energy

Potential difference

Potential difference measures the tendency to push electrons into the external circuit. It is the electromotive force between two points in the circuit

Standard conditions for measuring potential difference

• A pressure of 100kPa

• 1M concentration of solution

• Potential difference are usually measured at 25C

Standard electrode Potentials

The half cell should be constructed at standard conditions (gas pressures of 100kPa, concentration of 1M) and the temperature of 25C.

The cell is connected to a standard hydrogen electrode to form a galvanic cell and the potential difference is measured with a voltameter.

A standard is used because

When the conditions are not standard. the order of half reactions in electrochemical serieis may be different.