Ch 20
Download
1 / 31

Ch. 20 - PowerPoint PPT Presentation


  • 117 Views
  • Uploaded on

Ch. 20. Oxidation-Reduction Reactions. Types of Reactions. There are many different types of reactions: Redox Acid-Base Precipitation. 20.1 Oxidation and Reduction. Oxidation- Reduction Reaction : reaction in which electrons are transferred from one atom to another AKA- Redox Reaction.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Ch. 20' - flint


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Ch 20

Ch. 20

Oxidation-Reduction Reactions


Types of reactions
Types of Reactions

  • There are many different types of reactions:

  • Redox

  • Acid-Base

  • Precipitation


20 1 oxidation and reduction
20.1 Oxidation and Reduction

  • Oxidation- Reduction Reaction: reaction in which electrons are transferred from one atom to another

  • AKA- Redox Reaction


Oxidation

The roaring fire shown to the right is an example of the rapid oxidization of the hydrocarbons making up the wood and the reduction of the Oxygen gas from the air.

Oxidation


The, very rusty, Iron hammer is also being oxidized by the Oxygen in the air, but at a much slower rate than the burning wood.


How do oxidation and reduction differ
How do Oxidation and Reduction Differ? Oxygen in the air, but at a much slower rate than the burning wood.

  • Oxidation- loss of electrons

  • OIL – Oxidation is Loss

  • Ex: Na → Na+ + e-


Reduction
Reduction Oxygen in the air, but at a much slower rate than the burning wood.

  • Reduction- gain of electrons

  • RIG – Reduction is Gain

  • Ex: Cl + e- → Cl -


Oil rig
OIL RIG Oxygen in the air, but at a much slower rate than the burning wood.

  • Oxidation Is Loss

  • Reduction Is Gain


Changes in oxidation number
Changes in Oxidation number Oxygen in the air, but at a much slower rate than the burning wood.

  • Oxidation number – is the number of electrons lost or gained by the atom when it forms ions.

    • When an atom or ion is reduced, the oxidation number is lowered.

    • Oxidation numbers keep track of the movement of electrons in a redox reaction.


Oxidation numbers are written with the positive or negative sign BEFORE the number. (+ 3, - 2)

Ionic charge is written with the sign AFTER the number. (3+ , 2-)


Oxidation in redox reactions
Oxidation # in Redox Reactions sign BEFORE the number. (+ 3, - 2)

  • When an atom is oxidized, its oxidation number increases

  • When an atom is reduced, its oxidation number decreases


Oxidation in redox reactions1
Oxidation # in Redox Reactions sign BEFORE the number. (+ 3, - 2)

  • The Magnesium has been oxidized.

  • The Hydrogen has been reduced.

  • The Chlorine stayed the same.


Applications of redox chemistry

Removes tarnish from metal objects such as silver. sign BEFORE the number. (+ 3, - 2)

Applications of redox chemistry



Hydrogen peroxide is an antiseptic because it oxidizes biomolecules of germs. It also lightens hair because it oxidizes the dark pigment of the hair.



Assigning oxidation numbers
Assigning Oxidation Numbers oxidizing substance which will "bleach" the stains away

The oxidation number of an uncombined element is zero.

Includes diatomic molecules, subscripts don’t matter.

  • Examples:

    • Fe: oxidation number = 0

    • H2 : oxidation number = 0

    • S8: oxidation number = 0


The oxidation number of a monatomic ion is equal to the charge on the ion.

  • Examples:

    • Oxidation number of S2- is -2.

      Oxidation number of Al3+ is +3.

      Oxidation number of Ca2+is+2.


The charge on the ion.oxidation number of the more electronegative atom in a molecule or complex ion is the same as the charge it would have if it were an ion.

  • Ex: SiCl4 ; Cl is -1


Hydrogen (H) has two possible oxidation numbers: charge on the ion.

  • +1 when bonded to a nonmetal

  • -1 when bonded to a metal

    The oxidation number of fluorine (F) is always -1




Assigning oxidation numbers1
Assigning Oxidation Numbers charge on the ion.

Let's start with Carbon Dioxide, CO2.

1. Neutral compound charge = 0

2. Oxygen gets its standard charge of -2 for each oxygen atom.

3. In order to tally to zero, we MUST assign Carbon the oxidation number of +4.


Neutral charge on the ion.compound charge = 0

2. Chlorine is the most electronegative element charge of -1 for each Chlorine atom.

3. both Hydrogen atoms are given an oxidation number of +1.

4. In order to tally to zero, we MUST assign Carbon the oxidation number of 0.


Polyatomic
Polyatomic charge on the ion.

  • 1. This ion has a charge = 2-

  • 2. Oxygen gets its standard charge of

    -2 for each oxygen atom.

  • 3. In order to tally to zero, we MUST assign Sulfur the oxidation number of +6.


Oxidation number in redox reactions
Oxidation Number in Redox Reactions charge on the ion.

  • 1.When an atom is oxidized, its oxidation number increases.

  • 2. When an atom is reduced, its oxidation number decreases.


Acid base reactions
Acid-Base Reactions charge on the ion.

  • In an acid-base reaction, an acid and a base combine to produce a salt and water.

    • Recall: all acids start with H


Example of acid base reaction
Example of Acid-Base Reaction charge on the ion.

  • HCl(aq) + NaOH (aq)  NaCl (aq) + H2O (l)

  • Acid + Base  salt + water

  • How to identify acid-base?

    • All acids start with H

    • All acid-base produce water as a product


Precipitation reactions
Precipitation reactions charge on the ion.

  • In a precipitation reaction, two aqueous solutions are combined to form a solid precipitate, which settles out on standing.

  • 2FeCl3(aq) + Cu(SO4) (aq)  Fe2(SO4)3(aq) + 3CuCl2(s)

    • How to identify precipitation reaction

      • There is a small (s) on the product side of the reaction


How to identify a precipitate if not told
How to identify a precipitate if not told charge on the ion.

  • Use your solubility chart!!!!!!


ad