1:10 Electrode potentials and cells

How is an electrochemical cell made and the two reactions

How is a salt bridge usually made and what it does

Two different metals dipped in salt solutions of their own ions and connected by a wire (the external circuit). 2 reactions within are oxidation and reduction so it’s a redox process.

Filter paper soaked in KNO3(aq). It allows ions to move ,balance out the charge and complete the circuit

In what directions do the electrons flow in

How to measure voltage between two-half cells, and what does this show

More reactive to less reactive (or more negative electrode potential to more positive electrode potential)

Voltmeter measures the cell potential of the EMF (electromotive force or E cell)

What other half cells can you have apart from a metal in salt solution of their own ions.

Why is platinum used

Solutions of two aqueous ions of the same element such as Fe2+ / Fe3+ (aq). The conversion between the two happen on a platinum electrode.

Inert so wont react with ions.

In what way are half-equations written in

Which equation out of 2 half-equation swaps when writing out overall reaction

Zn2+ + 2e- → Zn (s) reduction direction ALWAYS

More reactive / more negative electrode potential

What does the SHE look like

What is the cell potential affected by so what conditions are used

What is measure using a SHE

Temp, pressure and conc. So we used standard conditions of:

Any solution must have a conc of 1.00 mol dm^-3 , temp must be 298K, pressure must be 100 KPa.

Standard electrode potential of the cell connected to the SHE is measured

How to work out the standard cell potential. where do you find these values

E cell = E reduced - E oxidised (all measured a standard conditions) found from the electrochemical series

Red I oxid II oxid I red

Double vertical lines represent a salt bridge and things in different phases are separated by a vertical line. half cell with more neg pot on lef, solid must always be on outside

(g) go closer to salt bridge and are usually separated by a phase line from (aq). If there is two ions and a H+ ion, H+ ones in the middle and the more pos metal ion goes closest to centre. Add Pt (s) if no solid present

What doe the standard cell potential look like if a reaction is feasible

What is a lithium battery made up of and the reaction equations at each electrode

How are lithium batteries recharged

It is positive

Lithium cobalt oxide (LiCoO2) electrode and graphite electrode. The electrolyte is lithium salt in an organic solvent.

At neg electrode : Li+ + e- <> Li

At pos electrode : Li+ + CoO2 + e- <> Li+[CoO2]-

Recharged by supply a current to force electrons o flow in opposite direction around the circuit and reverse the reactions. (Difficult and impossible to do this with non-rechargeable batteries) The equation is just the overall equation backwards for this.

How does a fuel cell differ from other cells

Draw a diagram, of an alkaline hydrogen-oxygen fuel cell. State relavent equations

What do the anion-exchange membranes allow to flow through

Fed chemicals to generate electricity it doesn’t contain / store them. They generate electric current and do not need to be electrically charged.

Allow anions (OH-) and water to pass through but not H2 and O2 gas. The electrolyte is alkaline KOH solution

Advantages and disadvantages of fuel cells

One thing that doesn’t change cell electrode potential

Ad:

More efficient they convert more of their available energy into kinetic energy. Internal combustion energies waste a lot of their energy producing heat.

Only waste product is water and no toxic chemicals or CO2 emissions from the cell

Don’t need to be electrically charged. Produce electricity as long as H2 and O2 are supplied

Disad:

Need energy to procure a supply of H2 and O2 via electrolysis of water and this requires electricity usually generated by burning fossil fuels. So the whole process usually isn’t carbon neutral.

H2 is highly flammable so need to be careful when handled or transported

Surface area of metal

Advantage of using methanol rather than hydrogen in a fuel cell

Why a fuel cell does not need to be electrically recharged

Why are values of acidic and alakaline hydrogen-oxygen fuel cell the same

It is a liquid so can be stored or transported easily

Reactants supplied continuously

Same overall reaction

Meaning of the term electrochemical series

In a SHE, what is the solution

how to allow a cell reaction to go to completion. At completion a voltmeter would read 0V. Why?

List of electrode potentials in numerical order

Acid such as HCl

remove voltmeter and add lamp

conc of ions in two solutions is equal