SQSM-09 - Chapter 9 Electrochemistry 1. What is a passive...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 9 Electrochemistry 9-1 1. What is a passive electrode? What quality in a metal is required to serve as a passive electrode? Give three examples of metals that would make good passive electrodes. A passive electrode is an electrode that does not participate in the reaction. Passive electrodes are inert metals that serve as the surface on which electrons are transferred between the external circuit and the media (often an aqueous solution) of the chemical reaction. In order for the metal to be inert, it must have a relatively positive standard reduction potential. Common passive electrodes are constructed from Ag, Pt, and Au. 3. Distinguish between a galvanic and an electrolytic cell. Which type of cell would be used to nickel plate a faucet? Which type of cell can act as a battery? A galvanic cell converts chemical potential energy into electrical potential energy, while an electrolytic cell converts electrical potential energy into chemical potential energy. Spontaneous electron transfer reactions give off free energy as they lower their chemical potential energy. The released energy is converted into electrical potential energy in a galvanic cell. Batteries are galvanic cells. Reactions in which the products are at a higher free energy than the reactants can be forced to the higher chemical potential energy by an external power supply in an electrolytic cell, which converts the electrical potential energy stored in the power supply into the higher chemical potential energy of the reactants. Nickel plating is done in an electrolytic cell. 5. Sn/Sn 2+ (1.0 M) and Zn/Zn 2+ (1.0 M). a) What is the anode half-reaction? The one with the more negative standard reduction potential Zn Zn 2+ + 2e 1- E ° anode = -0.76 V b) What is the cathode half-reaction? The one with the more positive standard reduction potential Sn 2+ + 2e 1- Sn E ° cathode = -0.14 V c) What is the cell reaction? Zn + Sn 2+ Zn + Sn d) What are the oxidizing and reducing agents? oxidizing = Sn reducing = Zn e) How many electrons are transferred in the cell reaction? 2 electrons f) What is the abbreviated form of the cell? Zn | Zn 2+ || Sn | Sn g) What is the cell potential? E ° cell = E ° - E ° a node = -0.14 – (-0.76) = 0.62 V 7. Au/Au 3+ (1.0 M)/ and ClO 3 1- (1.0 M)/ClO 4 1- (1.0 M). a) What is the anode half-reaction? The one with the less positive standard reduction potential ClO 3 1- + H 2 O ClO 4 1- + 2H 1+ + 2e 1- E ° anode = +1.19 V b) What is the cathode half-reaction? The one with the more positive standard reduction potential Au 3+ + 3e 1- Au E ° cathode = +1.50 V c) What is the cell reaction? 3ClO 3 1- + 3H 2 O + 2Au 3ClO 4 1- + 6H 1+ + 2Au d) What are the oxidizing and reducing agents? oxidizing = Au reducing = ClO 3 1- e) How many electrons are transferred in the cell reaction? 6 electrons f) What is the abbreviated form of the cell?
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

SQSM-09 - Chapter 9 Electrochemistry 1. What is a passive...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online