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May 21 - Chapter 17 textbook OXIDATION-REDUCTION. Objective :To determine O.N. for atoms in elements and compounds. HW : Complete worksheet. STUDY PAGE 606-607 from textbook. DO NOW OBSERVATION SKILLS!.

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May 21 chapter 17 textbook oxidation reduction
May 21 - Chapter 17 textbookOXIDATION-REDUCTION

Objective :To determine O.N. for atoms in elements and compounds.

HW : Complete worksheet. STUDY PAGE 606-607 from textbook


Do now observation skills
DO NOWOBSERVATION SKILLS!

  • In your notebook record the experiment in words and then describe the experiment like a chemist (with a CHEMICAL REACTION! )


  • Indicate the metal and the non metal

  • How metals react?

  • How non metals react?

  • Review : draw the dot diagram for each element, and for the compound formed

  • How many electrons and protons in each reactant?

  • How many electrons and protons in each element in the product?


Redox reactions electron transfer reactions
REDOX REACTIONS (electron transfer reactions)

Whenever an atom loses an electron another atom has to gain one. Both reactions are simultaneous.

Mg + O2  MgO

Magnesium lost 2 electrons because oxygen took them. The metal LOST electrons, the NON METAL GAINED electrons



Leo ger
LEOGER

Losing

Electrons is

Oxidation.

Gaining

Electrons is

Reduction


Oil rig
OIL RIG

Oxidation

Is

Loss.

Reduction

Is

Gain.


Redox reactions
REDOX REACTIONS

  • REDuction – OXidation reactions

  • Electrons are transferred from the element that is being oxidized to the one that is being reduced.


Oxidation number o n
Oxidation Number (O.N.)

Chemist use the O.N. to determine how many electrons are either gained or lost by an atom or ion in a chemical reaction.

O.N. is the charge or partial charge of an atom in a compound or an ion.


Rules for assigning o n
RULES FOR ASSIGNING O.N.

1. For all uncombined elements O.N. = O (FREE ELEMENTS)

2. For monoatomic ions the charge equals O.N.

3. Metals of group 1 in compounds O.N.= +1.

Metals of group 2 in compounds O.N.= +2


4. Fluorine in compounds is always – 1.

Other halogens -1 in binary compounds with metals.

5. Hydrogen + 1 except in metal hydrides (combined with metals of group 1 or 2)

6. Oxygen is -2 except when combined with F (is =2) or in peroxides (-1).


7. THE SUM OF THE OXIDATION NUMBERS IN ALL COMPOUNDS MUST BE ZERO

8. FOR POLYATOMIC IONS THE SUM OF THE O.N. IS EQUAL TO THE CHARGE OF THE ION


Group work
Group work ZERO

  • Get in your groups and practice what you just have learnt and complete handout.

  • Finish the rest for homework.


Review find the o n for each element
Review ZERO Find the O.N. for each element

  • Cl2

  • KH

  • Li2SO3

  • Na2NO2

  • NO3-

  • PO43-

  • CaCr2O7

  • OF2

  • H2O2


Answer to finding the oxidation state
Answer to finding the Oxidation state ZERO

  • +7

  • +5

  • +5

  • +7

  • +4

  • +6

  • +2

  • +3 17. 0

  • +5 18. 0

  • +3 19. +6

  • +6 20. +3

  • 0 21. +5

  • +2 22. +4

  • +5 23. -2

  • +4 24. -2

  • +4


May 22
May 22 ZERO

Objective: How to keep track of electron transfers in chemical reactions?

HW: finish worksheet and read page 604 to 605.

Answer question 1 from page 611


Do now observation skills1
DO NOW ZERO OBSERVATION SKILLS!

  • In your notebook record the experiment in words and then describe the experiment like a chemist (with a CHEMICAL REACTION! )


Practice
PRACTICE ZERO

  • HCl + Mg -> MgCl2 + H2

  • Indicate the oxidation state of each element in the reaction.

  • READ HANDOUT “ANALYZING OXIDATION-REDUCTION REACTIONS”


Vocabulary
VOCABULARY ZERO

  • SIMULTANEOUS = at the same time

  • OXIDATION = to lose electrons

  • REDUCTION = to gain electrons

  • OXIDATION NUMBER = charge or partial charge over an element.

  • SPECIE = Can be an element or an ion.


How to recognize which specie get oxidized and which gets reduced
How to recognize which specie get oxidized and which gets reduced?

The specie that gets oxidized loses electrons and its oxidation number increases.

The specie that gets reduced gains electrons and its oxidation number decreases.


Half reactions p 608
Half reduced?reactions(p 608)

A redox reaction can always be broken down as 2 half reactions that show the atom or ion that is being oxidized and the one that is being reduced.

MASS AND CHARGE has to be conserved in a half reaction

1. find the o.n. of each element in the reaction. Determine which is being reduced an which is being oxidized


2. Balance the masses first reduced?

3. Complete each half reaction with electrons.( LEO GER)

4. Verify that masses and charges are balanced.


Make up lab opportunity
MAKE UP LAB OPPORTUNITY reduced?

  • Type the observation for the redox reactions done in class, describing the physical appearance of the reactants and the products. Indicate which was the evidence of a chemical reaction. (change in color, bubbles, formation of a precipitate).

  • For each reaction write both half reactions.

  • Indicate the reduction and oxidation reaction half reactions and the oxidizing and reducing agents.

  • On top of page type name of your lab teacher and lab period.


May 24
May 24 reduced?

  • How to recognize oxidizing and reducing agents?

  • How to recognize redox reactions?


Do now observation skills2
DO NOW reduced?OBSERVATION SKILLS!

  • In your notebook record the experiment in words and then describe the experiment like a chemist (with a CHEMICAL REACTION! )


Agents
AGENTS reduced?

  • They are always found in the reactants side.


Reducing agent
REDUCING AGENT reduced?

  • When a substance is oxidized it LOSES electrons. Its O.N. increases. It is being oxidized and is making the other substance in the reaction reduced. Then the one that gets oxidized is the REDUCING AGENT.

    R.A. gets oxidized.

    Its O.N. increases

    Active metals are good RA


Oxidizing agents
OXIDIZING AGENTS reduced?

  • When a substance is reduced it GAINS electrons .

  • Its O.N. decreases. It is being reduced, it takes electrons from the other specie, it makes the other specie to get oxidize.

  • The one that gets reduced is the OXIDIZING AGENT

  • Oxidizing Agent : Gets reduced

  • Its ON decreases.


  • 2Mg + O reduced?2  MgO

  • Mg: oxidation number changes from

  • 0 to +2 . It increased.

  • Mg gets oxidized. Is the reducing agent.

  • Oxygen: Oxidation number changes from 0 to -2 , it decreases is the Oxidizing agent.


To recognize redox reactions
To recognize redox reactions… reduced?

Look for changes in the oxidation number or the atoms. If one element changed the O.N. then for SURE is redox reaction.

All single replacement, synthesis, decomposition and combustion reactions are REDOX.

Double replacement reactions are not redox.


Practice your turn
PRACTICE – your turn! reduced?

  • Get in your group and work with the reactions in the handout. Determine the O.N. for each element and decide which element got oxidized and which got reduced (TIP ALWAYS IN THE REACTANTS SIDE!!!). Indicate the O.A and R.A.

  • For your assigned reaction copy in color paper, write the half reaction indicating oxidation and reduction.

  • Complete sentence for your reaction.


Complete for your reaction
Complete for your reaction reduced?

  • _____ got reduced and is the oxidizing agent. Its O.N. decreased from ______ to_______ .

  • _____ got oxidized and is the reducing agent. Its O.N. increased from ______ to _______ .


May 28
May 28 reduced?

Objetive: Spontaneous Redox Reaction

To use table J to predict if a single replacement reaction will occurr.


Activity series
Activity series reduced?

Spontaneous Reactions : happen without external help.

CuSO4 + Zn  Zn SO4 + Cu

In a single replacement reaction the most active element replaces the other element from a compound. (TABLE J)


Table j
Table J reduced?

The metal above gets oxidized the one below will get reduced.

For non metals the one above gets reduced the one below gets oxidized.


F reduced?2 + NaCl

I2 + NaCl 

Cl2 + Na I 


Metals in table j
METALS IN TABLE J reduced?

The higher the metal is in table J, the most active it is, the more tendency to became oxidized (lose electrons)

On Top of table J best reducing agents

Towards the bottom metals tend to gain electrons then they became reduced and are good reducing agents


Non metals
Non Metals reduced?

F2 has the greatest tendency to gain electrons ( became reduced) is the BEST OXIDIZING AGENT.


Predict if the reaction will occur
Predict if the reaction will occur reduced?

Ag (NO3) + Cu 

Zn+2 + Co 

MgCl2 + Ni 

K + FeCl3 

Li + Mg 2+


Predict if the reaction will occur1
Predict if the reaction will occur reduced?

Ag (NO3) + Cu 

Zn+2 + Co 

MgCl2 + Ni 

K + FeCl3 

Li + Mg 2+


May 29 electrochemistry
May 29 reduced?ELECTROCHEMISTRY

  • OBJECTIVE: To distinguish between electrochemical and electrolytic cells

  • To identify the different parts of a cell and explain their purpose.


Do now
Do now reduced?

What SPONTANEOUS reaction would occur if we have

Cu, Cu2+, Zn and Zn2+ together.

Hint USE TABLE J

Where the electrons flow? Which loses which gains?


Voltaic cells p 613
Voltaic Cells (P 613) reduced?

In spontaneous oxidation-reduction (redox) reactions, electrons are transferred and energy is released.


IDEA! reduced?

If we can place the two metals in two different containers and connect them with a wire the electrons will flow from the Zn to the Cu and we will have an electric current – ELECTRICITY

But it does not work if we do not close the circuit – USE A SALT BRIDGE


Voltaic cells
Voltaic Cells reduced?

  • A typical cell looks like this.

  • The oxidation occurs at the anode.

  • The reduction occurs at the cathode.


Electrodes
ELECTRODES reduced?

  • Where the reduction or oxidation takes place. They are usually metals or they can be made of graphite.

  • RED CAT

  • REDuction at the cathode


Electrochemistry
ELECTROCHEMISTRY reduced?

*Anode: where the oxidation occurs.

*Cathode: where the reduction occurs.

Voltaic or galvanic cell: produce ELECTRICITY from an spontaneous chemical reaction.


ELECTRON FLOW. FROM THE ONE THAT GETS OXIDIZED TO THE ONE THAT GETS REDUCED.

POLARITIES

ANODE – NEGATIVE source of electrons

CATHODE- POSITIVE


A typical voltaic cell THAT GETS REDUCED.

RED CAT

REDuction at the cathode

Cathode: the electrode at which reduction occurs

Anode: the electrode at which oxidation occurs

Salt bridge: a tube containing strong electrolyte, a pathway to allow the ions to move from one side to another. PERMIT THE MIGRATION OF IONS


Problems THAT GETS REDUCED.

1. A cell uses the reaction Mn + Ni2+ Ni + Mn2+ to produce electricity.

Write the half-reaction that occurs at the anode.

b) Write the half-reaction that occurs at the cathode.

c) Which species in this cell loses electrons?

d) As the cell produces electricity, which ion increases in concentration?

Mn Mn2+ + 2e-

Ni2+ + 2e-  Ni

Mn

Mn2+


1. Voltaic Cell THAT GETS REDUCED.

A type of electrochemical cell that converts chemical energy to electrical energy by a spontaneous redox reaction.

In 1800, Volta built the voltaic pile and discovered the first practical method of generating electricity. Constructed of alternating discs of zinc and copper, with pieces of cardboard soaked in salt water b/w the metals, the voltaic pile produced electrical current.


Electrochemical cell THAT GETS REDUCED.

An apparatus that uses a redox reaction to produce electrical energy (voltaic cell) or uses electrical energy to cause a chemical reaction (electrolytic cell).


Electrolytic cell 626
Electrolytic THAT GETS REDUCED.cell (626)

Uses electricity to force a reaction that is not spontaneous to occur.

NOTICE THAT IN ELECTROLYTIC CELLS THERE IS A BATTERY OR A POWER SOURCE PRESENT

Electrolysis: to decompose a substance using electricity


Electroplating
Electroplating THAT GETS REDUCED.

Is used to cover an object with metal using electricity.

THE OBJECT TO BE COVERED GOES IN THE CATHODE

POLARITIES : ANODE – POSITIVE

CATHODE- NEGATIVE SOURCE OF ELECTRONS – CONNECTED TO NEGATIVE


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