redox and electrode potentials Flashcards
how do we balance redox reactions for acidic conditions
1) first write half equations making sure they are balanced.
2)add in water to balance the oxygen atoms and hydrogen to balance the hydrogen atoms
3)add in electrons to balance the charges
4) balance the electrons
5) cancel and put equations together
how do you balance redox equations for alkaline conditions
1) form half equations , making sure the elements are balanced
2) add in water to balance the oxygen atoms
3) add in hydrogen ions to balance the hydrogen atoms
4) add in OH- ions in replace for H+ ions on both sides of equations
3) form H20 from H+ and OH- ions
4)add electrons to balance the charges
5) balance the eletrons , cancel and combine
what is a redox titration
a redox titration involves an oxidising agent being titrated against a reducing agent. electrons are transferred from one species to another
- you dont always need an indicator as redox titrations using titration metal ions naturally change colour when changing oxidation state
what is a voltaic cell
a voltaic cell converts chemical energy into electrical energy . a voltaic cell can be made by connecting together two different half cells , allowing electrons to flow
what are the two ways you can create a half cell
1) a metal rod dipped into a solution of its aqeous metal ions
2)or with 2 ions of the same element in different oxidation states and a platinum electrode
why do we use a platinum electrode
because they are inert
what does the line in Zn2+ | Zn represent
a phase boundary , as Zn2+ is aqueous and Zn is solid
what is standard electrode potential (E theta)
tells us the tendency of a half cell to gain or lose electrons
how do we measure the standard electrode potential
we use the standard hydrogen electrode , as this has a standard electrode potential of 0 V and therefore tells us the standard electrode potential of the other half cell
what are the conditions of the standard hydrogen electrode
1moldm-3 solution and H2 gas at 298k and 100 kpa and a platinum electrode inside
what does the salt bridge do
allows the ions to flow
how do you know which half cell donates the electrons and which gains the electrons
the more negative electrode potential half cell is the one which donates the electrons and is the reducing agent
how do we work out standard cell potential
draw out half cell using lines
- the right side minus the left side and the left side has the more negative standard electrode potential
