Galvanic and redox Flashcards
What is a galvanic cell
A type of electrochemical cell that converts chemical energy to electrical energy
What is the type of galvinc cell called for that one with two seprate beakers, stalt bridge drenched and circuit and stuff
Daniel cell
What are galvanic cells used for
Used to demonstrate the direction of electron flow from one electrode to another, generating electricity than heat from exothermic reactions
What do you include when draweing a galvanic cell
- Anode electrode
- Cathode electrode
- Polarity of each half cell
- The direction of electron flow
- The direction of ions in the salt bridge
- two half equations (reduction and oxidation)
- Overall equation
- Saltbridge
- External ciruit
- Electrolyte of each half cell
What are the types of electrodes and when would you use them
- Metal electrode- when one of the conjugate pair is a metal
- PLatinum or carbon electrode- inert - used when no metal is present in conjugate pair
- Gas chamber electrode- intert metal with a gas chamber- when one of the conjugate pairs is a gas
What is the external circuit
the two electrodes are connected through conducting wires, allowing for electron flow
What is the internal circuit
the salt bridge that allows for the movement of ions in the solution
What does the globe in galvanic cell convert the chemical energy into?
Light and heat
what is an example of a salt bridge
any substance that allows for ions to flow through and is inert.
eg. kNO3
what kind of reaction occurs in a galvanic cell
spontaneous redox reactions
what happens in each annode and cathode
oxidation occurs in anode
reduction occurs in cathode
why seperation of the half cells good for galvanic cells
it FORCES for electrons to flow from the anode half cell to the cathode half cell via the external circuit.
What are observations (Must be visual)
- The zinc anode is decreasing in size, forming zinc ions in the solution. ( so like degrading)
- Using data booklet, changes in solution colour
- Electrons are accepted and solid is formed, therefore cathode increasing in size ( plating)
- If gas shit- bubbles being formed
- The galovometer moving, indicationg a chemical reaction is occuring due to electrical energy being produced.
cations go to and anions go to?
cations go to cathode
anions go to anode
why do you need the salt bridge
to complete the internal circuit and and to maintain electrical neutrality by allowing for the flow of ions in the two half cells
What will happen if salt bridge is removed
The anode will undergo oxidation which will cause for the loss of electrons, making the half cell net postively charged.
The cathode will undergo reduction will cause for the gain of electrons, making the half cell net negatively charged.
The postively charged annode half cell will attract the electrons and
the negatively charged cathode half cell will repel the electrons.
Therefore no more elctron flow will occur.
whats the equation for electromotive force(emf)/potential difference between two half cells
and whats the unit
E°(cell) = E°(cathode)– E°(anode)
V (volts)
true or false
Emf measured at standard conditions(100kPa, 298K and 1Msolution)
true
How are E° of other half cells are
measured
Using a Standard Hydrogen Electrode (SHE). It has a assigned EMF value of 0 volts. You connect it to half cell and form a galvanic cell.
What are the rules for oxidation number
- O.N. of an atom in its elemental form is zero eg Cu(s) N2(g) both have
O.N. zero - O.N. of simple ions is the charge of the ion eg Na+ O.N. is +1 for Na
and S2- O.N. for S is -2 - O.N. for H in compounds with non metals is +1
- O.N. for oxygen in a compound is usually -2
- Sum of O.N. of all elements in a compound is zero
- Sum of O.N. of all elements in an ion equals charge of the ion
- Hydrogen in hydrides( with metals such as NaH , MgH2) - (-1)
If the oxidation number of an element is increased then, and what if the oxidation number of an element is decreased
Oxidised
Reduced
What is the charge of ionic compounds
the charge carried by the cations and anions respectively
Why cant you assign oxidation numbers for elements using periodic table for covalent compounds
Because in covalent compounds,electrons are shared between atoms. so instead O.N is determined through electronegativity( eg. H20, H= +1 and O= -2)
Oxidation is the gain/loss of electrons
Reduction is the gains/loss of electrons
Oxidation loss
Reduction gain
