Flashcards in 23.4 - Electrode potentials Deck (19):
What energy transfer takes places in an electrochemical cell?
Chemical --> Electrical
What does a half-cell consist of?
Metal rod dipped in a solution of its metal ion (aq)
Write the equation for the equilibrium in a half-cell for Zinc
Zn 2+ (aq) + 2e- --> Zn (s)
What does an ion/ion half-cell contain?
Contains ions of the same element in different oxidation states (aq)
Metal electrode = Platinum (Pt)
What is the negative electrode?
The electrode with the more reactive metal which loses electrons and so becomes oxidised
What is the positive electrode?
Less reactive metal
Define standard electrode potential
The emf of a half-cell compared with a standard H half-cell, measured at 298 K with solution concentrations of 1 mol dm-3 and a gas pressure of 100 kPa
What does standard electrode potential measure?
The tendency to be reduced and gain electrons
What is the standard electrode potential of a standard hydrogen electrode?
What connects the 2 electrodes?
What is the purpose of the wire?
Allows a controlled flow of electrons
What connects the 2 solution?
What is the purpose of a salt bridge?
Allows ions to flow
What does a common salt bridge contain?
Filter paper soaked in KNO3 (aq)
What is the trend of decreasing negativity of standard electrode potential values?
The greater the tendency to lose electrons
Greater tendency so undergo oxidation
What does a more positive standard electrode potential value mean?
Greater the reactivity of a non-metal in gaining electrons
Outline the procedure used to measure standard cell potentials
1) Prepare 2 standard half-cells at standard conditions
2) Connect metal electrodes to a voltmeter
3) Prepare a salt bridge
4) Connect 2 solution of the half-cells with a salt bridge
5) Record the standard cell potential from the voltmeter
How would you calculate standard cell potential?
Standard electrode potential (positive electrode) - standard electrode potential (negative electrode)