Electrochemistry
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Answer is A Although equation 1 is oxidised and needs to be flipped it’s emf still stays the same E(right) - E(left) = Emf = 0.34 - -0.44 = 0.78
What happens when you dip a rod of a metal into its own ions
An equilibrium is set between the solid metal and aqueous metal ions
Write the half equation for Zinc (s) to Zinc (ii)
What is the simplest salt bridge made of
Filter paper soaked in a saturated solution of KNO3
Why are salt bridges necessary
To complete the circuit by allowing ion movement between the half cells to balance the charges, without reacting with the electrodes or aqueous metal ions within each half cell
What does a ______ Represent 1) | 2) ||
1) Phase change (solid liquid gas) 2) Salt bridge
How would an aluminium copper cell be represented
In electrochemistry what happens at the left hand electrode
Left hand electrode is where oxidisation occurs Left hand electrode is the half cell with the most negative E Cell value
In electrochemistry what happens at the right hand electrode
Right hand electrode is where reduction occurs Right hand electrode is the half cell with most positive e cell
Draw the standard hydrogen Electrode
What conditions is the standard hydrogen electrode used in
Temperature = 298K Pressure = 100KPA [H+] = 1 MOLDM^-3
What is the standard hydrogen electrode used for
Universal standard for the Comparing of other cells against the E Cell of the standard hydrogen electrode E cell of standard hydrogen electrode e= OV
Why might the standard electrode not be used
Cheaper to use another comparison then the SHE As SHE has platinum Provides just as a good reference
If an E Cell is more negative what does it mean
Better reducing agent (easier to oxidise)
If an E Cell is more positive what does it mean
Better oxidising agent (Easier to reduce)
What factors alter E Cell value
Concentration of ions Temperature
What happens if you reduce the concentration of the ions in the left hand half cell
Equilibrium moves to the left to oppose the change of removing ions (in reduced form) This releases more electrons the E Cell of the left hand cell becomes more negative So EMF increases
How do you calculate the emf from e cell value
E Cell = ERight - ELeft
When would you use a platinum electrodes Why is it chosen
When both oxidised and reduced forms of the metal are in aqueous solution (no solids) Inert and a good conductor
How would you predict if a reaction would occur
Take 2 half equations Find species that is being reduced (RHS electrode) Calculate its e cell - the e cell of the oxidised species If E Cell > 0 reaction will occur
What is the Daniel Cell made from
Zinc/Copper(II)
What is the cell for disposable batteries made from
Zinc/Carbon
What reactions take place in a disposable battery
2NH4+ + 2e- ——> 2NH3 + H2
What reactions occur in a lead acid batter (Car Battery)
