1 / 17

Redox Reactions

Redox Reactions. Redox Reactions. Reactants: Zn + I 2. Product: Zn I 2. Redox Equations: At the conclusion of our time together, you should be able to:. Define redox Figure out oxidation numbers for any element Show the change in oxidation numbers in a reaction.

cece
Download Presentation

Redox Reactions

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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Redox Reactions

  2. Redox Reactions Reactants: Zn + I2 Product: Zn I2

  3. Redox Equations:At the conclusion of our time together, you should be able to: Define redox Figure out oxidation numbers for any element Show the change in oxidation numbers in a reaction

  4. C3H8O + CrO3 + H2SO4 Cr2(SO4)3 + C3H6O + H2O What’s the Point ? REDOX reactions are important in … • Electrical production (batteries, fuel cells) • Purifying metals (e.g. Al, Na, Li) • Producing gases (e.g. Cl2, O2, H2) • Electroplating metals • Protecting metals from corrosion • Balancing complex chemical equations • Sensors and machines (e.g. pH meter)

  5. What is Redox? • REDOX stands for REDuction/OXidation • Oxidation is often thought of as a combination of a substance with oxygen (rusting, burning) • Oxidation refers to a loss of electrons • Reduction refers to a gain of electrons • As a mnemonic remember LEO says GER • Lose Electrons = Oxidation • Gain Electrons = Reduction

  6. Let’s See How You’re Doing?? Q- What is oxidation? What is reduction? Represent each as a chemical equation. oxidation = loss of e– … X  X+ + e– reduction = gain of e– … X + e–  X– Q- Why are 2Na + Cl2 2NaCl & 2H2 + O2 H2O considered redox reactions? Both involve the transfer of electrons. (Na has no charge, the atoms in diatomic molecules have no partial charge. After reaction the atoms have different shares of the electrons because of different EN values)

  7. Let’s See How You’re Doing?? Q- Is it possible to oxidize a material without reducing something else? No. A lost e– is taken up by something else.

  8. Determination of Oxidation and Reduction • If oxidation # decreased; substance reduced • If oxidation # increased; substance oxidized

  9. Review of Oxidation Numbers • We will see that there is a simple way to keep track of oxidation and reduction • This is done via “oxidation numbers” • An oxidation number is the charge an atom would have if electrons in its bonds belonged completely to the more electronegative atom • e.g. in HCl, Cl has a higher EN. Thus, oxidation numbers are Cl = -1, H = +1

  10. Review of Oxidation Numbers 1. Any element, when not combined with atoms of a different element, has an oxidation # of zero. (O in O2 is zero, Na by itself is zero) 2. Any simple monatomic ion (one-atom ion) has an oxidation number equal to its charge (Na+ is +1, O2– is –2) 3. The sum of the oxidation numbers of all of the atoms in a formula must equal the charge written for the formula. (if the oxidation number of O is –2, then in CO32– the oxidation number of C is +4)

  11. Review of Oxidation Numbers 4. In compounds, the oxidation # of IA metals is +1, IIA is +2, IIIA is +3, Zn & Cd is +2, Ag is +1. 5. In ionic compounds, the oxidation # of a nonmetal or polyatomic ion is equal to the charge of its associated ion. (MgCl2, Mg is +2, therefore Cl is –1) 6. F is always –1, O is always –2 (unless combined with F), H is usually +1, except when it is bonded to metals in binary compounds. (ex. NaH, H oxidation # is –1or when it’s in elemental form H2, oxidation # is 0).

  12. Oxidation numbers of all the elements in the following ? IF7 NaIO3 F = -1 Na = +1 O = -2 7x(-1) + ? = 0 3x(-2) + 1 + ? = 0 Therefore, I = +5 Therefore, I = +7

  13. Redox Equations:Let’s see if you can: Define redox Figure out oxidation numbers for any element Show the change in oxidation numbers in a reaction

  14. Let’s Apply the Oxidation Rules Rule (from earlier slide) Total Ox.# or rule 5 6 3 6 6 3 6 4 3 6 3 6 6 4 5 +2 +5 -8 +1 +5 -6 +2 +12 -14 -4 +6 -2 +1 -1 +1 +5 -2 +1 +5 -2 +1 +6 -2 -2 +1 -2 +1 -1 H N O 3 K2Cr2O7 C2H6O AgI H2PO4–

  15. Corrosion – Deterioration of Metals by Electrochemical Process Determine and balance the reaction, determine what is oxidized and what is reduced.

  16. Corrosion of Silver Ag + O2 Ag2O 4 Ag + O2  2 Ag2O Each Ag loses 1e- Each O gains 2e- Silver = oxidized Oxygen = reduced Silver = reducing agent Oxygen = oxidizing agent

More Related