REDOX REACTIONS PT 1

PG 111-148

What 2 things happen during a redox reaction

• Electron transfer

• Oxidation nd reduction happen simultaneously

Define: Redox reaction

A reaction involving the transfer of electrons

Define oxidation

Oxidation is the loss of electrons

Define reduction

Reduction is the gain of electrons

Define reducing agent

(and what is it interlinked with)

The substance that donates electrons

(oxidation)

Define Oxidizing agent

(and what is it interlinked with)

The substance that accepts electrons

(reduction)

What does OIL RIG stand for

Oxidation is loss of electrons

Reduction is gain of electrons

In an oxidation half reaction the O. No. of the _____ increases

In a reduction half reaction the O. No. of the ______ decreases

reducing agent

oxidising agent

Define electrolyte

• Substance that can conduct electricity due to present of free ions when molten or dissolved in solution

Whats the difference between Oxidation number and charge

O. No. =It's a bookkeeping tool to track the hypothetical loss or gain of electrons by an atom in a molecule, based on electronegativity. It indicates the hypothetical charge an atom would have if all bonds were completely ionic

Charge = It refers to the actual net electric charge of an atom, molecule, or ion. 

It's determined by the difference between the number of protons (positive) and electrons (negative

Define Anode

The electrode where oxidation takes place

Define Cathode

The electrode where reduction takes place

In a Standard Electrode Potential table the forward reaction is the____ and the reverse reaction is the _____

• Reduction

• Oxidation

On the SPE table ____is read ____

• Reduction

• Oxidation

• Left to right ( this is how we normally READ)

• Right to left

On the table, where are the weak OA’s? Therefore say the rest

• Upper left

• Strong OA bottom left

• Strong RA Upper right

• Weak RA bottom right

( Just think* Right side of table, Reducing agent

Are all redox reactions reversible

YES

When comparing two half reactions always look at

also when asked to write a half reaction,what must you never do

• Stronger reducing agent: Readily lose electrons

• Stronger oxidising agent: Readily gains electrons

*Write a double arrow

how are reduction half reactions read on sep table and oxidation half-reactions read

• Left to right

• Right to left

The higher the E^0 values on the table, the

… greater chance that a substance will be reduced

What’s a key thing to do when writing a net ionic reaction

• Balance the electrons on the left and right side of the half-reactions

O No. increases=___electrons=_____=_____agent

O No. decreases=____ electrons=____=_____ agent

= lose(since it become more +)= oxidised= reducing agent

=Gain(became more -)=reduced=oxidizing agent

What are the two electrochemical cells

Galvanic(voltaic)

Electrolytic

What’s the difference between an E-cell and G-cell (3)

E-cell:

• Non-spontaneous

• E pot. is smaller than 0V

• Electrical energy into chemical energy

G-Cell:

• Spontaneous (Strong RA and Strong OA)

• E pot. is bigger than 0V

• Chemical energy into electrical energy

• Exothermic

What does a galvanic cell have(4)

pg142-143*

-Electrodes of the metal half-reaction

-electrolytes that have the same metal

-Conducting wires to connect electrodes in ext. circuit

-Salt bridge that connects to half-cells electrolyte solution

Oxidation happens at the_____ and reduction happens at the

• Anode

• Cathode

Mass of the anode ____

Mass of cathode ____

Decreases

Increases

Where do the ____flow:

• Electrons

• Anions

• Cations

• From anode to cathode

• From Cathode half-cell to Anode half-cell

• From anode half-cell to cathode half-call

Define Galvanic/voltaic cell

A g/v cell is an electrochemical call in which spontaneous.self-sustainable redox reactions occut at the electrodes. Chemical energy is converted to electrical energy

What is a salt bridge

Salt bridge is a glass tube with a suitable electrolyte that has weak RAs and OAs so that they don’t react with ions in the two half cells as anions and cations are being transferred through it

What is the purpose of the salt bridge

It ensures that the solutions remains:

• Electrically neutral

• Current flows continuously

What’s an ideal salt solution to use in a salt bridge and give 3 reasons why

Potasium nitrare (KNO3)

• K is a weak OA

• NO3 is a weak RA

• K and NO3 salts are soluble in water so no precipitate will form

All reactions on the SPE table are written according to their ability to ______. The more_____ the values the _____ the ______ takes place

• Gain electrons

• Positive

• Easier

• Reduction

How is cell notation written

pg 145

ALL REDOX REACTIONS ARE EQUILIBRIUM REACTIONS AND CAN BE INFLUENCED BY CONDITIONS( T,C,P)

Changes in these conditions influence what?

The emf of the cell

What are the standard conditions at which electrode potentials are determined?

• Electrolyte concentration (1 mol.dm-3)

• Temp= 25C

• Pressure(ONLY if gas is present)= 101kPa (1atm)