Topic 14- Further Redox

Question 1

Define standard electrode potential

Answer 1

the emf of a half-cell measured relative to the standard hydrogen electrode, all solutions at 1moldm-3 concentration and 1atm pressure/ 101Kpa and at 298K

Question 2

What happens when a rod of metal into a solution of its own ions?

Answer 2

an equilibrium is set up between the solid metal and the aqueous metal ions

Question 3

What are the half equations for an acidic hydrogen-oxygen fuel cell?

Answer 3

negative electrode: H2(g) –> 2e- + 2H+

positive electrode: 0.5O2(g) + 2H+(aq) + 2e- —> H2O(l)

Question 4

What is the overall equation for both an acidic and alkali hydrogen-fuel cell?

Answer 4

0.5O2 + H2(g) —> H2O(l)

Question 5

What are the half equations for an alkali hydrogen-oxygen fuel cell?

Answer 5

negative electrode: H2(g) + 2OH-(aq) —> 2H2O(l) + 2e-

positive electrode: 0.5O2(g) + 2H+(aq) + 2e- —> 2H2O(l)

Question 6

What are the standard conditions?

Answer 6

• gas pressure, 100kPa
• temperature, 298K
• concentration of ions in solution, 1moldm-3

Question 7

What is the simplest salt bridge made out of?

Answer 7

filter paper soaked in a saturated solution of potassium nitrate, KNO3

Question 8

Why are salt bridges necessary?

Answer 8

they complete the electrical circuit, allowing a flow of charge through ion movement
also contain inert ions so they don’t react with the electrodes