teachemrosinski.files.wordpress.com · web viewelectrochemistryunit 13 page 1 learning objective: i...

ElectrochemistryUnit 13

Learning Objective:I can determine the oxidation state for any atom in an element, ion, or compound.

I can explain what happens in an oxidation-reduction, or redox, reaction. Criteria for Success:

I can determine the oxidation state for an atom in an element.I can determine the oxidation state for an atom in an ion.

I can determine the oxidation state for an atom in a compound. I can identify the species being oxidized in a redox reaction.I can identify the species being reduced in a redox reaction.

Introduction to Oxidation-Reduction ReactionsA. Any chemical process in which electrons are transferred from one atom to another is an _________-__________ reaction.1. The name for this type of reaction is often shortened to what is called a ________ reaction.2. A species _____ _________ when _______ (LEO).

A species _____ ________ when _______ (GER).

3. ___________________________ (OIL).

____________________________(RIG).

Oxidation Numbers/StatesA. Chemists assign a number to each element in a reaction called an _________________ state that allows him/her to determine the electron flow in the reaction.

1. Even though they look like them, oxidation states are not _________ charges! 2. Oxidation numbers can be assigned to each atom in an element, ion, or compound…whether the compound

is ____________ or ___________________! 3. Oxidation states are imaginary charges assigned based on a set of rules simply used to determine

_________________ flow.

Rules for Assigning Oxidation Numbers (In order of priority):1. The oxidation number of any pure element is _________. 2. The oxidation number of a monatomic ion is __________ to its charge. 3. The ______ of the oxidation numbers in a compound is zero if ____________, or equal to the ___________ if a

polyatomic ion. 4. The oxidation number of alkali metals in compounds is _____, and that of alkaline earths in compounds is

______. The oxidation number of F is ______ in all its compounds.5. The oxidation number of H is _____ in most compounds. Exceptions are H2 (where H = 0) and the ionic

hydrides, such as NaH (where H = -1).6. The oxidation number of oxygen (O) is ______ in most compounds. Exceptions are O2 (where O = 0) and

peroxides, such as H2O2 or Na2O2, where O = -1.7. For other elements, you can usually use rule (3) to solve for the unknown oxidation number.

Examples:N2(g) elemental state, so N = 0. N3-(g) monatomic ion, so N = -3.NO(g) has O = -2, so N = +2.NO2(g) has O = -2, so N = +4.SO4

2- has O = -2. Thus x + 4(-2) = -2. Solving the equation gives x = -2 + 8 = +6.K2Cr2O7 has K = +1 and O = -2. Thus 2(+1) + 2 x + 7(-2) = 0; 2 x = 12; Cr = +6.

B. In general, redox reactions will be any type of reaction except ___________________________________.

1. However, there are exceptions so you should always check if electrons have been_____________.

Identifying Oxidation-Reduction Reactions

A. In order to identify a REDOX reaction, write the _________ number for each ________ in the reaction as outlined in the

rules above.

1. A substance that has the element that has been ________ (LOST electrons) will have an oxidation number that

becomes more ________.

2. A substance that has the element that has been ________ (GAINED electrons) will have an oxidation number

that becomes more ________.

B. ___________ are produced in oxidation and acquired in reduction. Therefore, for reduction to occur, oxidation must

occur _____________. Each process is referred to as a ___________.

Oxidation Half-Reaction Reduction Half-ReactionZn(s)→ Zn2+(aq) + 2e- Fe2+(aq)+ 2e-→ Fe(s)


Learning Target:I can explain the process of oxidation and reduction in a chemical reaction.

Criteria for Success:

I can explain the purpose of the reduction potential chart.I can use the reduction potential chart to determine which species is more likely to be oxidized or reduced.

Half ReactionsA _____________________ is either the oxidation or reduction reaction component of a redox reaction. A half reaction is

obtained by considering the change in __________________states of individual substances involved in the redox reaction

and adding _______________________ (e-) to balance the charges

Oxidation Half-Reaction Reduction Half-ReactionAl(s) → Al3+(aq) + 3e- Cu2+(aq) + 2e- → Cu(s)

Reduction Potiential Values

1. ______________________________ is a measure of the tendency of a chemical species to acquire electrons and thereby be reduced. Reduction potential is measured in _________________ (V), or millivolts (mV).

2. Reduction potential values are measured _______________to the potential for H+ to ____________ electrons to become H2.

3. On the reduction potential chart, the more __________________________ EOV is the more likely it is to be reduced (gain electrons) and the more _____________________ the less likely it is to be reduced (gain electrons)

4. However, just because a certain half reaction is positive does _________ mean that it will always be reduced

(gain electrons). Again, these values are ___________________to the tendency for H+ to be reduced to form H2

How does reduction potential compare to the activity series?

Balancing Redox ReactionsA. We can determine the potential difference of a redox reaction by a balanced redox reaction.

1. Determine the Net ionic equation from the balanced chemical equation.2. Separate the half reaction from the net ionic equation.3. Multiply each equation across so that you have the same number of electrons (e-) on both sides4. Look up the reduction potential for each equation. You must change the sign of the equation being

oxidized. DO NOT MULTIPLY THE REDUCTION POTENTIALS!!!!5. Add the equations together

B. When considering the sign of the reaction potential of the balanced redox equation, a positive sign indicates that the reaction is spontaneous and a negative sign indicates the reaction is nonspontaneous.


Content Objective:I can make qualitative or quantitative predictions about galvanic (voltaic) cells based on half-cell reactions and

potentials and analyze these cells to identify properties of the underlying redox reactions.

A. Galvanic Cells

1. In Pre-AP Chemistry, we deal mostly with reactions that are _________________________________—meaning, they will

happen on their own if all the “ingredients” are present.

2. __________________________ cells use thermodynamically-favored (spontaneous) REDOX reactions to produce

electrical energy via a flow of ____________________ (also known as Voltaic cells or batteries).

a. In short: galvanic (voltaic) cells produce current

3. To use that current, we need to __________________the place where oxidation is occurring from the place where

reduction is occurring.

*QUICK REMINDERS*1) Oxidation is LOSS of electrons 2) Reduction is GAIN of electrons

OIL (LEO) RIG (GER) Ex: Zn (s) Zn2+ (aq) + 2e- Ex: Cu2+ (aq) + 2e- Cu(s)

B. Parts of the Galvanic Cell

1. ___________________________: ALWAYS through the wire from anode to cathode (alpha order)

2. ____________ (–): the electrode where oxidation occurs (may appear smaller over time)

3. _________________ (+) : the electrode where reduction occurs (may appear larger over time)

4. _______________________ (disk): bridge between cells whose purpose is to provide ions to balance the charge

5. ____________________: measures the cell potential (emf or E°) in volts

(Label here)

(Label here)

(Label here)

(Label here)

(Label here)

(Label here)

(Label here)

C. Terms to remember through shortcuts

________________: the cathode is + in galvanic/voltaic cells, and so the anode is negative

________________: oxidation occurs at the anode (may show mass decrease)

________________: reduction occurs at the cathode (may show mass increase)

________________: electrons in a voltaic/galvanic cell ALWAYS flow From the Anode To the

CAThode

o And the cat gets fat! (cathode gains mass over time)

o “ANODE”-rexic! (anode loses mass over time)

D. Standard Reduction Potential for a Galvanic/Voltaic Cell (E°)

1. In a galvanic (voltaic) cell, the metal with the ____________ (more positive) reduction potential will be

reduced!

2. Because the values come from a chart of standard __________________ potentials, you MUST REVERSE the sign of

the E° of the oxidized species before adding to the E° of the reduced species.

3. How to calculate the cell potential of a galvanic cell: Eoox = - Eo

red and Eocell = Eo

oxidation + Eoreduction

4. For a spontaneous oxidation-reduction (voltaic/galvanic cell) to occur, the overall cell potential must

be ________________.

Example: Consider the half reactions shown below and the standard electrode reduction potentials that follow.

Cu2+(aq) + 2 e- Cu(s) Eo = +0.34 V

Zn2+(aq) + 2 e- Zn(s) Eo = -0.76 V

a) Which one has the GREATER (more positive) reduction potential? Cu2+ or Zn2+

(If it has the GREATER reduction potential (Eo), it has a greater desire for electrons and will be _________________!)

Keep the equation the same since it’s being reduced: Cu2+(aq) + 2 e- Cu(s)

Therefore: Eored = +0.34 V

b) Zinc has the LOWER reduction potential (Eo), so it will be oxidized. (Flip the sign of the Eo!)

Flip the equation since it is being oxidized: Zn (s) Zn2+(aq) + 2e-

Therefore: Eoox = - Eo

red = -(-0.76 V) = +0.76 V

c) Now calculate Eocell by plugging in the numbers: Eo

cell = Eoox + Eo

red = 0.34 + 0.76 = 1.10 V

****Galvanic (Voltaic) cells should ALWAYS have a positive Eocell value!!!!!!!!!!!!!****

d) Take your half reactions, balance, and find the net ionic equation.

Cu2+(aq) + 2 e- Cu(s)

Zn (s) Zn2+(aq) + 2e-

Cu2+(aq) + Zn(s) Zn2+(aq) + Cu(s)

Nuclear ChemistryUnit 13

Learning Target:I can describe the characteristics of alpha, beta, and gamma radiation.

Criteria for Success:I can define nuclide.

I can list six characteristics of stable nuclides.I can determine whether a nuclide is stable or unstable.

Introduction to Nuclear ChemistryThe Nucleus1. In nuclear chemistry, an atom is referred to as a ____________ and is identified by the number of ________________ and _______________. In nuclear chemistry the focus is on the nucleus of the atom.

a. _________________ are represented in one of the two following ways.

1.

2. b. Another general name for protons or neutrons is ______________.

Characteristics of a Stable NuclideA. It may seem surprising that a large number of _______________ can reside within the small volume of the nucleus. A close distances, however, a strong force of attraction, called the _____________ _________ exists between nucleons. ______________ are very involved in this force.

1. Atoms having low atomic numbers (up to about ___) are more stable when the neutron-proton ratio is ________.2. Atoms having large atomic numbers are more stable when there are greater numbers of _______________ than ________________.3. No stable nuclides exist for atoms with atomic numbers greater than _____.4. Stable nuclides tend to have even numbers of both ________________ and __________________.5. According to the nuclear __________ model, nucleons exist in different energy levels, or shells, in the nucleus. Nuclei with 2, 8, 20, 28, 50, or 82 protons or 2,8, 20, 28, 50, 82, or 126 neutrons are generally more stable than those that do not contain these numbers of nucleons. These are known as ___________ numbers. 6. Stable nuclides have a number of neutrons that is _______ to or ________ than the number of protons. Except hydrogen-1 and helium-3.

The Band of StabilityUnit 13

Band of StabilityNot all nuclides are stable and will therefore not fall in this band of stability. Nuclides that lie to the left of the band of stability

have too many neutrons to be stable and will usually decay by emitting beta particles. Nuclides that lie to the right of the band of stability have too many protons and will decay by electron capture or positron emission. Nuclides of elements that are above the

band of stability or have an atomic number greater than 83 have too many protons and neutrons and will decay by emitting alpha particles.


Learning Target:I can describe the characteristics of alpha, beta, and gamma radiation.

Criteria for Success:I can define radioactive decay.

I can explain why an unstable nuclide will undergo radioactive decay.I can describe three different types of radioactive decay in terms of balanced nuclear equations.

Radioactive Decay

Unstable Nuclides1. An unstable nuclide is also known as a _____________________ nuclide.

A. A _____________________ nuclide will undergo ______________________ ______________ in order to form a more stable nuclide.

1. _________________________ ____________ is the spontaneous disintegration of a nucleus into a slightly lighter nucleus, accompanied by the emission of particles, electromagnetic radiation, or both.

Types of Radioactive Decay Unstable Nuclides Undergo

Alpha Decay( )α1. In alpha emission ( ), an alpha particle, which is two ______________ and two _____________ bound together, is αemitted from the nucleus.

a. Restricted almost entirely to ____________ nuclei.b. Alpha particles have relatively _______ penetrating power and can be stopped with a sheet of ________.

Beta Decay ( )β1. Beta EmissionIf a neutron is converted to a ____________ and an ___________ and the electron is emitted from the nucleus, the electron that is emitted is known as a beta particle.

a. Occurs when a nuclide is above the band of stability because it has too many ___________ to be stable. b. Beta particles have ________________ penetrating power and can be stopped with a sheet of ________________ foil or plastic.

2. Electron CaptureIn electron capture, an inner orbital electron is captured by the _____________ of its own atom, combines with a ____________ and forms a ________________.a. Occurs when a nuclide has too many ___________.

Gamma Decay( )γ1. In gamma emission, high-energy electromagnetic waves are emitted from the ____________ as it changes from an excited state to a ground energy state.

a. Usually occurs immediately following other types of decay.b. Gamma rays have __________ penetrating power and require thick sheets of ____________ or concrete to be significantly reduced.


Learning Target:I can compare fusion and fission reactions.

Criteria for Success:I can identify a fission reaction.I can identify a fusion reaction.

I can describe nuclear equations for fission and fusion reactions.I can differentiate between nuclear decay reactions, nuclear fission reactions and nuclear fusion reactions (by

description, properties, images and equations).

Fission and Fusion A. When the nuclei of certain isotopes are bombarded with ____________, the nuclei split into ___________ fragments. This process is called ______________.

1. During nuclear _______________ additional _________________ are released and cause the fission of other atoms.2. In a _____________ ________________, some of the emitted ___________ react with other fissionable atoms, which emit ___________ that react with still more fissionable atoms. 3. Nuclear ______________ releases enormous amounts of ______________.4. Fission occurs in __________ weapons and ___________ power plants.

5. The following are examples of fission reactions.

B. __________ occurs when nuclei ____________ to produce a nucleus of greater mass.1. ________________ reactions, in which small nuclei combine, release much more _____________ than _____________ reactions, in which large nuclei are split and form smaller nuclei.2. ____________ only occurs at very high ___________________.3. Fusion reactions occur in _____________ (our sun included) and the _________________ bomb.

4. The following are examples of fusion reactions.

teachemrosinski.files.wordpress.com · web viewelectrochemistryunit 13 page 1 learning objective: i...

Documents