Electro chemical cells

Electrochemical cell is a device that is capable of either generating electric energy from chemical reaction or using electrical energy to cause chemical reactions

A battery is define as two or more electric cells connected in series to produce a steady flow of current

• - A non rechargeable battery
• - Once chemical reaction is complete, the battery is done

• - batteries are rechargeable
• - products form reactants (reaction is reversible)

• - Batteries that need to continuously add at least one of the reactants to the cell
• - Hydrogen must be continuously pumped into the cell

• 1) -  A cell that converts a chemical energy from a redox reaction into electrical energy
• - this is known as the voltaic cell
• 2) - A cell that converts electrical energy into chemical energy causing a redox reaction 
• - this is know as the electrolytic cell.

• - are device that spontaneously produces electrify by redox 
• - uses chemical substances that will participate in a spontaneous redox reaction
• - composed of two half cells, consisting of metal rods or strips immersed in a solution of its own ions
• - Electrodes: a solid conductor connecting the cell to an external circuit 
• - Anode: an electrode where oxidation occurs
• - Cathode: an electrode where reduction occurs 
• - the electrons flow from the anode to the cathode (a before c) through an electrical circuit
• - To maintained cell neutrality porous boundary/ salt bridge is added to separate the two electrolytes while still allowing ions to flow.

Cations (positively charged ions) move from the salt bridge into the solution in the cathode compartment to maintain an electrically neutral solution.

Anions (negatively charged ions) move from the salt brigade into the solution in the anode compartment to maintain an electrically neutral solution.

Voltaic cells can be represented as cell notation

anode|electrolyte||electrolyte|cathode

Electrolyte are minerals in your body or other body fluids that carry an electrical charge.

SOA present in Voltaic cells always undergoes reduction at the cathode

SRA in Voltaic cells always undergoes oxidation at the anode

• - lacking the ability or strength to move 
• - chemically inactive

• - Chemical substances that do not participate in the reactions
• - needed when the SOA and SRA involved in the reaction are not solid. Usually graphite solid (C(s)) or platinum strip.

A standard cell is a voltaic cell where each half cell contain all entities necessary at SATP and all aqueous solution have a concentration of 1mol/L

• - a cell that converts electrical energy into chemical energy causing a redox reaction.
• - a cell in which a nonspontaneous redox reaction is forced to occur
• - a combination of two electrodes, an electrolyte and an external power source. 

The cell potential of an electrolytic cell will always be negative.

The Anode, when it shrinks its colour becomes darker

Th Cathode, when it grows its colour becomes lighter

• - Anode shrinking
• - Cathode growing
• - electrolyte becoming less acidic (H+ is being consumed)
• - electrolyte becoming less basic (OH- is being consumed)

The Anode will shrink if the anode is the actual SRA

The cathode will grow if the cathode is the actual SOA

• - Is the measure of the potential difference between two half cells. 
• - Formula: E°cell = E°rcathode - E°ranonde 
• - E° is the standard reduction potential
• - The higher the E° the stronger the OA
• - All standard reduction potential is based on the standard hydrogen cell being 0.00V. This means all standard reduction potential that are positive are stronger OA’s and hydrogen and all negative is weak OA’s than hydrogen. 
• - If E° is positive = spontaneous reaction
• - If E° is negative = non spontaneous reaction

When E°Cell is positive the reaction is spontaneous 

When E°Cell is negative the reaction is non-spontaneous.

Standard Reduction measures the tendency of a given chemical to be reduced

Makes a comparison and scientific study easier

The Standard reduction potential can be determined using a zero point/reference point 

A zero point/reference point is a chosen half cell/reaction to compare other half reactions. In our data booklet the zero point is hydrogen

• - Use the 5 step method and write the reduction potentials of the Cathode (SOA) and the Anode (SRA)
• - If required write the minimum voltage required to force the reaction to occur (the minimum voltage is the cell potential)

• - Anode always shrinks, cathode grows
• - Anode decreases in mass and Cathode increases in mass

- Most common inert electrode are Graphite (carbon), platinum (Pt), gold (Au) and rhodium(Rh)

- No, Cu is not an inert electrode because it’s a reactive electrode

• 1) Production of elements 
• - Molten ionic compounds are used to form metals at the cathode and non metal at the anode 
• - Molten ionic compound instead of Aqueous solution because some water react with metal

• - Remove impurities or unwanted elements
• - improve (something) by making small changes

Occurs in an electrolytic cell, when an aqueous solution containing chloride ions (chloride ions and water are the only RA’s) goes through electrolysis, the chloride ion will become the strongest reducing agent even though water is lower on the table

Mixed with foreign material

• 2) Refining of metals (Electrorefining) - impure solid are oxidized to aqueous cations
• - the anode is the impure metal and the cathode is the pure sample of the desired metal
• - (In a nutshell) the process of purifying the impure metal of the anode with the pure metal of the cathode

• 3) Electroplating - the process of covering one metal with another
• - The substance you want to cover is the cathode (protects from rusting)

usually done on cars

- A moist environment (water) and oxygen

- The deterioration (worsening) of a material as a result of its interaction with its surrounding.

• - Presence of salt in water, speed up the reaction (corrosion) 
• - Low pH acid

• 1) Painting - Iron or steel can be painted to prevent the attack or water and oxygen
• 2) Greases and oil can be applied to objects that cannot be painted (moving objects 
• 3) Coating or Plating - Iron objects are covered with a tough layer of another metal 
• 4) Sacrificial Anode - a stronger reducing agent (than cathode) highly active metals that are used to prevent a less active material surface from corroding. 
• - will shrink in size and the iron object will not be damage
• - Sacrificial Anodes will lose electrons
• - Usually Mg or Zn
• 5) Catholic protection - uses a direct source of electrons to prevent corrosion. (Electrical outlet, battery)

• 1) Write the balance equation for the half reaction of the substance being consumed or reduced
• 2) Convert the given measurements to an amount in moles 
• 3) Calculate the amount of the required substance using mole ratio
• 4) Convert calculated amount to the asked/final quantity.