TUTTEE ACADEMY LOGO
broken image
  • Home
  • About Us
  • Subjects 
    • CHEMISTRY
    • BIOLOGY
    • PHYSICS
    • MATHEMATICS
    • PSYCHOLOGY
    • ECONOMICS
    • BUSINESS
    • COMPUTER SCIENCE
    • CHINESE
    • ENGLISH
    • SPANISH
    • IBDP IA / EE
    • IBDP TOK
    • ONLINE TUTORIAL
  • Exam Boards 
    • IBDP
    • IBMYP
    • IGCSE & GCSE
    • HKDSE
    • GCE A-LEVELS
  • Courses 
    • IBDP Tuition
    • GCE A-Level Tuition
    • IBMYP Tuition
    • I/GCSE Tuition
    • HKDSE Tuition
  • Admission Test Prep 
    • PREDICTED GRADE
    • SAT / SSAT
    • UKISET (UK)
    • BMAT
    • UKCAT / UCAT
    • LNAT
    • TMUA (Cambridge)
  • Student Results 
    • IBDP STUDENT RESULTS
    • IGCSE & GCSE MATHEMATICS
    • A-LEVEL STUDENT RESULTS
    • IGCSE STUDENT RESULTS
    • GCSE STUDENT RESULTS (UK)
    • HKDSE STUDENT RESULTS
    • OUR STORIES
  • Question Bank
  • Resources
SCHEDULE A LESSON NOW

A2/A-level Chemistry: Standard Electrode Potential

Topic 3.1.11 -

· A Level,A2 Chemistry,electrode,standard potential,electrochemistry

Let's go over some specific terms about electrochemistry mentioned in A-level Chemistry!

Definition

  • Electromotive force (E.m.f.): the ‘push’ that a cell is able to provide to a current flowing through it (volts)
  • Standard electrode potentials (SEP): the potential difference of a half-cell relative to the standard hydrogen electrode (SHE)

Electrochemical cell

  • e.g. zinc-copper cell
  • Component: zinc and copper electrode, metal ion solution, salt bridge, high-resistance voltmeter
  • Oxidation: Zn electrode loses electron to form zn2+ ions
  • Reduction: Cu2+ ions in solution gain electrons to form Cu metal
  • Zinc electrode decreases in mass while copper electrode increases
broken image
  • Half-cell potential for copper = +0.34V
  • Half-cell potential for zinc = -0.76V
  • Overall reaction potential = Eoreduction – Eooxidation = 1.10V
  • E.m.f. calculated by reversing the least positive value then add up two half-cell potentials (if not familiar with the minus sign)
  • For a feasible reaction, cell potential MUST BE POSITIVE (usually over +0.6V)

Measurement of standard potential with SHE

Standard hydrogen electrode (SHE)

broken image
  • Reference half-cell (with standard potential 0.00V)
  • Used to measure other electrode potential
  • Condition: Hydrogen gas at 1 atm pressure, 298K, inert platinum electrode in 1.00 mol dm-3 H+(aq) ions
broken image
  • Anode: Metal electrode
  • Cathode: Standard Hydrogen Electrode (SHE)
  • other components include metal electrolyte, sald bridge, voltmeter
  • Oxidation half-cell: Metal(s)  ---> Metal ion(aq) + electrons
  • Reduction half-cell: H+(aq) + electron ---> 1/2 H2(g)
  • Overall reaction: Metal(s) + H+(aq) ---> Metal ion(aq) + H2(g)
broken image
  • In A-level Chemistry, the condition of standard potential is always at 1 atm pressure and 298K
  • Stronger oxidising agent with the more positive Ecell is on LHS of the equation.

  • Stronger reducing agent with the more negative Ecell is on RHS of the equation. 
  • **Strong oxidizing agent = weak reducing agent, vice versa

Remarks:

  • Eºcell > +0.6V ---> reaction should go to completion
  • 0V < Eºcell < +0.6V ---> products predominate
  • -0.6V < Eºcell < 0V ---> reactants predominate
  • Eºcell < -0.6V ---> NO reaction

Limitations

  • A reaction with a positive Eºcell  may not actually take place – gives no indication of reaction rate
  • The reaction conditions may be very different from standard conditions
  • SEPs ONLY apply to aqueous equilibria, still there are many reactions that take place which are not in aqueous solutions

That's all~

broken image

CLICK HERE TO LEARN MORE ABOUT OUR A-LEVEL CHEMISTRY COURSES

SIGN UP FOR A-LEVEL CHEMISTRY TRIAL NOW!
Subscribe
Previous
AS/ A-Level Biology: Digestive System
Next
A2/A-level Chemistry: Summary of analytic techniques
 Return to site
Profile picture
Cancel
Cookie Use
We use cookies to improve browsing experience, security, and data collection. By accepting, you agree to the use of cookies for advertising and analytics. You can change your cookie settings at any time. Learn More
Accept all
Settings
Decline All
Cookie Settings
Necessary Cookies
These cookies enable core functionality such as security, network management, and accessibility. These cookies can’t be switched off.
Analytics Cookies
These cookies help us better understand how visitors interact with our website and help us discover errors.
Preferences Cookies
These cookies allow the website to remember choices you've made to provide enhanced functionality and personalization.
Save