Energy, Electrons, and Protons

Question 1

For a reaction involving protons E_m will vary with what?

Answer 1

pH

Question 2

Why does binding of H+ binding depend on pH?

Answer 2

Due to pKa

Question 3

For a given redox reaction is number of electrons or protons constant?

Answer 3

Number of electrons

Question 4

What is plotted in order to estimate the pKa’s of groups that affect the pH dependence of E_m?

Answer 4

E_m vs pH

Question 5

What else can affect the relationship between reduction potential and pH?

Answer 5

Other protonatable groups on the redox centre

Question 6

What is used instead of a SHE?

Answer 6

An alternative reference electrode with a known potential

Question 7

Give 2 examples of alternatives used in place of the SHE

Answer 7

• Saturated calomel electrode
• Silver chloride electrode

Question 8

What are the 2 approaches to redox titration?

Answer 8

• Mix the oxidised and reduced versions of the molecule in known ratios and measure the resulting potentials
• Titrate the reduction potential of the redox couple with small amounts of oxidant/reductant
• at each point measure the potential of the solution of the solution and estimate the amount of redox species in oxidised/reduced state

Question 9

What is needed in order to be able to estimate the amount of redox species in the oxidised or reduced state?

Answer 9

Must be a difference in a measurable parameter between the oxidised and reduced states of the species