Chem: galvanic cells/fuel cells

what is a galvanic cell

electrochemical cell that converts chemical energy into electrical energy through redox reactions involving two different electrodes.

what is a redox reatcion

A chemical reaction that involves the transfer of electrons between two species, resulting in oxidation and reduction.

what is a spontaneous raecitons

A chemical reaction that occurs naturally. all galvanic cells are spontaneous

helf cells

galvanic cells have two half cells. one oxidation and one reduction

electrode

terminal that conducts eletricity. one postiive and one negtaive

cathode

positive electrode. site of reduction

anode

negative electrode. site of oxidation

electrolyte

solution contaninf ions that conducts electricity

salt bridge

internal circuit of cations and anions which neutralises the charge. needed to occur.

cell potential difference

the difference in electric potential between the anode and cathode in an electrochemical cell, measured in volts. It represents the ability of the cell to drive an electric current.

what does cell potential difference show

It shows the voltage generated by an electrochemical cell, indicating its capacity to drive electrical current. how strong e are pushed

formula cell potential difference

Ecell = Ecathode - Eanode

E of galvanic cell

always positive because its spontaneous

direct spontaneous reatciom

same container, no seperation of half cells, physical transfer of electrons, energy lost as heat

indirect spontanoues raetion

half reations are physically split, connected by a wire and salt bridge, energy is trasnferred to electriity (galvanic cell)

battery

combintaion of multiple cells in a series

primary cell

glavanic cell that cannot be recharged

types of primary cells

dry cell, alkaline, button cell

properties of primary cells

single use, non rechargeable, small/cheap/portable, redox reaciton is irreversible

two types of galvanic cells/batteris

primary cell and secondary cell

secondary cell properties

multi use, rechargeable, redox reaction is reversible and occurs many times

why are primary cells non rechargeable

redox reactions reactions that produce electricity are irreversible, meaning the chemicals cannot be converted back to their original state

examples of primary cell uses

include flashlights, smoke detectors, and remote controls.

what devices use primary cells

small, long life, portable devices that require minimal power use.

cell potential/difference/e cell

the voltage or electromotive force (EMF) that drives electrons between electrodes in a cell. difference in reduction potential between the cathode and anode.

how is E of a half cell measured using SHE

The standard electrode potential of a half-cell is determined by connecting it to the standard hydrogen electrode under standard conditions and measuring the cell voltage relative to the SHE, which is assigned 0.00 V.

what is SHE

Standard Hydrogen Electrode, a reference point for measuring electrode potentials. (0.00V at SLCwhat are)

what are SLC

Standard Laboratory Conditions (SLC) refer to the conditions under which electrochemical measurements are taken, typically at a temperature of 25°C and a pressure of 1 atm/100kPa.

what are fuel cells

type of glavani ccell that converts chemical energyu into electrical energy, rewuirng a cotnatn source of fuel

do fuel cells need to be reahcraged

no because as long as tehre is a constant supply of reactatns (fuesl) thaere is a constant supply of electricity

uses of fuel cell

both portable and fixed applicaitons. cars buses commnercial energy and backup power supply

efficiecy of fuel cells

high efficiencies almost no pollution, often between 40% to 60% efficeint, up to 85% heat produced also used for electricity

limitation of galvani cells

small amount of reactants, once they are consumed they cannot be regenrated

difference of fuel cell to notmal galvanic

galvacni reactants are stored in teh cell whereas fuel cells reactants are continously supplied from an external source

fuel cell components

include anode, cathode, electrolyte (H+ or OH- ions), and external circuit, porous electrodes, alkaline or acidic

what is the oxidising agent in the fuel cell

oxygen whcih is reduced at the cathode (+)

two types of fuel cells

alkaline and acidic

what does connecting multiple fuel cells produce

a fuel cell stack that increases voltage and power output.

alkaline fuel cell

hydorgen gas (feul) is oxidised at the anode by reacting with OH- ions and oxygen gas is reduced at teh cathode.

acidic fuel cells

hydorgen gas is oxidiesd at the anode and oxygen gas is reduced at the cathodes, involves H+ ions

voltage of alklaine and acidic fuel cells

both produce electricity, but alkaline fuel cells typically have higher efficiency and longer lifespan compared to acidic fuel cells.

energu loss of fuel cells.

they do not lose energy compared to combusiton wchi does. fuel cells are more efficient and produice smaller volume of GHG

how effieicnt are fuel cells

40-60% effieicnt, (HIGH)

what do they use the waste heat as

they use the waste heat to produce steam that can be used in turbines, rasing efficieny up to 85%

why msut the electrode be condustincg and porous

allows hydrogen and oxygen to come in contact with the tions in the lectriletes and to allows the redoc reactions to occur.

what determines teh current size that is drawn from a fuel cell

surface area of teh electrodes

what do the catalysts in teh elctrode do

enhance rate of reaction and current

advantages of fuel cells

include high efficiency, low GHG emissions, ability to operate continuously with proper fuel supply, onsite/no connection to grid

disadvantages of fuel cells

constatn fuel supply, expensive, lack of hydorgen filling station, impurities in hydorgen fuel, hydrogen unsafe (highly flammable)

fuel cell definition:

"a type of galvanic cell that converts chemical energy into electrical energy, requiring a constant source of fuel"

catalyst

substance that increases reaction rate by lowering the activation energy required

where is the fuel oxidised

at the anode (H2 gas)

alkaline

aka basic (greater PH than 7)

significance of porous

holes that allow the gas (reactatns) to flow through and make contacts wieth the elctrolytes/ions (whcih are needed to make the redox reaction pccur)

fuel cell uses/functions

transportation (vehicles,cars,buses), staionary power generation for buildings, backup power (off grid), and portable power sources.

energy transformation of galv/fuel cells

convert chemical energy into electrical energy through spontaenous redox reactions

primary galvanic cell effiiciency

60-90% efficient

fuel cell efficieny

typically 40-60% efficient, up to 85% if teh heat produced is used to geenrate electricity

how do porous electroed surface area help fuel cells

high surface area relative to the physical size of the electrode provides more active sites for catalysis to come in contact with molecules, enhancing the reaction rate.

in a FUEL cell oxygen is:

always reduced at the cathode