[23.5] predictions from electrode potentials

Question 1

what does the value of the standard electrode potential tell us about the system?

Answer 1

• most negative system has the greatest tendency to be oxidised and lost electrons
• most positive system has the greatest tendency to be reduced and gain electrons

Question 2

how do you find the strongest reducing and oxidising agent?

Answer 2

• strongest reducing agent = unoxidised version of most negative SEP (most postive)
• strongest oxidising agent = oxidised version of most positive SEP (most negative)

Question 3

how can you predict whether a reaction will take place?

Answer 3

knowledge of the standard electrode potentials for the two half cells

Question 4

when might reactions not be feasible?

Answer 4

if electrons flow from the more positive to the more negative

Question 5

what direction do redox systems react?

Answer 5

• redox system with more positive SEP value will react from left to right, and gain electrons
• redox system with more negative SEP value will react from right to left, and lose electrons

Question 6

what are the limitations of predictions using SEP values?

Answer 6

• indicate thermodynamic feasibility but give no indication of rate of reaction
• SEP are measured using concentrations of 1 mol dm⁻³, so if this changes, the value of the electrode potential will be different from the standard value
• reaction may not take place in standard conditions
• SEPs only apply to aqueous equilibria

Question 7

describe the effect of changing concentration on SEPs (based on more negative SEP)

Answer 7

• if concentration of ions increases, equilibrium shifts to the right, removing electrons from the system and making the electrode potential less negative
• if concentration of ions decreases, equilibrium shifts to the left, adding electrons to the system and making the electrode potnetial more negative
• any change to the electrode potential will affect the value of the overall cell potential

Question 8

standard electrode potentials and ΔG

Answer 8

• if SEP is positive, ΔG will be negative
• the smaller the value of the SEP, the less negative the value of ΔG