Redox

Terms

100

The loss of electrons

Oxidation

200

Electrode at which oxidation takes place

Anode

300

A reactant, often a non-metal, that causes another reactant to lose electrons

Oxidation agent

400

The potential difference generated by a voltaic cell in which a particular half-cell under standard condition is connected to a standard hydrogen half-cell

Standard electrode potential

500

An arrangement consisting of two half-cells connected internally by a salt bridge and externally by wires.

Voltaic cell

Redox Equation

100

Oxidation number: ? : ON=0 ? : ON=charge on the ion ? : ON=-2(usually) ? : ON=+1(usually)

Pure elements Ions Combined oxygen Combined hydrogen

200

1___ + 2____ --> 3____ + 4_____ 1 to 3: accepts electrons, undergoes reduction, decreases its oxidation number 2 to 4: donates electrons/ undergoes oxidation, increases its oxidation number

1: Oxidizing agent 2: Reducing agent 3: Conjugate reducing agent 4: conjugate oxidizing agent

300

CuO(s) + Zn(s) --> ZnO(s) + Cu(s) half equations of Oxidation___ : --> Reduction ___ : -->

Oxidation of Zinc: Zn --> Zn2+ + 2e- Reduction of copper ions: Cu2+ 2e- --> Cu

400

Write the equations of oxidation of SO2 to SO4(2-) in acidic solution

SO2 + 2H2O --> SO4(2-) + 4H(+) + 2e(-)

500

Write the equations of reduction of Cr2O7(2-) to Cr(3+) in acidic solution

Cr2O7(2-) + 14H(+) + 6e(-) --> 2Cr(3+) + 7H2O

Voltaic & Electrolytic cells 1

100

____ use the energy released in spontaneous redox reaction to generate electricity.

Voltaic cells

200

Voltaic cells: Ocidation occurs at ___ Reduction occurs at ___ Electrolytic cells: Ocidation occurs at ___ Reduction occurs at ___

Anode/ cathode Anode/ cathode

300

Voltaic cells are composed of two 1___, each containing a 2___ pair. Each 1___ contains an electrode and an electrolyte. 1___ are connected 3 ex/internally by wiring and 4 ex/internally by a 5____.

1: half-cells 2: conjugate redox pair 3: externally 4: internally 5: salt bridge

400

In electrolytic cells: the strongest oxidizing agent is __ at the __(-) the strongest reducing agent is __ at the __(+)

reduced/ cathode oxidized/ anode

500

In electrolytic cells, power source supplies electrons to ___ and accepts electrons from ___

oxidizing agent/ reducing agent

Voltaic & Electrolytic cells 2

100

Non-spontaneous endothermic reactions require electrical energy, which is converted into chemical energy

Electrolytic cells

200

Voltaic Cell: Anode is + or - Cathode is + or - Electrolytic Cell: Anode is + or - Cathode is + or -

-/+ +/-

300

It is an electrolytic conductor, conducting current by the flow of ions. What is it? and example?

Salt bridge/ KNO3

400

Three differences between voltaic cells and electrolytic cells

salt bridge/ no salt bridge anode(-),cathode(+)/anode(+),cathode(-) external circuit/ internal (power source supplies) spontaneous/non-spontaneous etc

500

Draw Electrolytic cells nicely

http://www.google.com.sg/imgres?start=87&um=1&hl=en&sa=N&biw=1092&bih=480&addh=36&tbm=isch&tbnid=d94DiuqMVbjKYM:&imgrefurl=http://electrochem.cwru.edu/encycl/art-m03-machining.htm&docid=U1vjz1tYe7GRfM&imgurl=http://electrochem.cwru.edu/encycl/fig/m03/m03-f02b.jpg&w=916&h=671&ei=_hBKUJixH4jprAfzn4CgAw&zoom=1&iact=hc&vpx=261&vpy=177&dur=5936&hovh=192&hovw=263&tx=163&ty=163&sig=104582705213400993178&page=7&tbnh=136&tbnw=186&ndsp=15&ved=1t:429,r:11,s:87,i:41

Questions

100

Voltaic cell is constructed using Ni(2+)/Ni and Zn(2+)/Zn. 1. which is the anode? 2. which has a negative charge? 3. will lose mass?

Zn/Zn/Zn

200

Write a balanced equation for combustion of ethanol

C2H5OH + 3O2 --> 2CO2 + 3H2O

300

Using the activity series shown in table 10.4.1 p. 320, write ionic equations for any reaction that would occur when cadmium is added to a solution of Cu(NO3)2.

Cu(2+) + Cd --> Cu + Cd(2+)

400

Explain why it would be unwise to store silver nitrate solution in a copper container.

it will dissolve the Cu container

500

A solution of hydrogen peroxide reacts with itself over time to produce water and oxygen gas and so solutions of hydrogen peroxide are generally kept in the refrigerator. If I add manganese dioxide, what is the role of this? How does it affect the reaction?

catalyst - increase the rate of reaction