Homework
Textbook assignment: Read Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 3: Sections 8 to 9.
3.8 Oxidation-Reduction Reactionsl. All oxidation-reduction reactions (redox reactions) involve electron transfers between the reactants to form the new components. While it may seem like the rules for redox reactions and assignment of oxidation numbers are somewhat arbitrary, they are based on the electron configuration and affinity characteristics of the atoms involved in the exchange.
3.9 Classifying Reactions. A reaction occurring in water-based solution is often classified as one (or more!) of four types: precipitation, salt-forming acid/base, gas-forming, or oxidation-reduction (electron transfer). Note the characteristics of each, and that a given reaction may fall into more than one classification category.
Half-reaction | Electron Transfer | Result |
---|---|---|
X → Xn+ + n e- | X tranfers electrons to Y | X is oxidized and is the reducing agent |
Y + ne- → Yn- | Y accepts electrons from X | Y is reduced and is the oxidizing agent |
Atom or Molecule Type | Oxidation Number | Example |
---|---|---|
Atom in Pure Element | Zero | I2: each I = 0 |
Monatomic ion | Charge on ion | Mg2+: +2 |
Fluorine in compound | -1 | FI: F is -1, I is therefore +1 |
Oxygen in compound | -2 | H2O: O is -2, each H is +1 EXCEPTIONS: in FO, O is +1 in peroxides, O is -1 in superoxides, O is -1/2 |
Halogens Cl, Br, and I in compounds | -1 | NaCl: Cl is -1; Na is therefore +1 Exceptions: with O or F ClO-: Cl is +1 |
Hydrogen | +1 | H2O: O is -2, each H is +1 EXCEPTIONS: in metal hydrides, H is -1 CaH2: Ca is +2, each H is -1 |
Neutrally charged compound | Sum of oxidation values is zero | H2O: 2 * -+1 + -2 = 0 |
Charged polyatomic ion | Sume of oxidation values equals charge | PO4-3- Each O: -2 total -8 P: +5 Net: -8 + 5 = -3 |
Read the following weblecture before chat: Reduction-Oxidation (REDOX) Reactions
Review the Videos at Thinkwell Video Lessons under REACTIONS IN AQUEOUS SOLUTIONS.
Optional Websites:
If you are still having problems, yo may find the oxidation-reduction reactions from Lumen Learning useful, as well as this oxidation numbers calculator.
Determination of water in copper sulfate pentahydrate and sodium hydrogen carbonate
What is the Amount of Water in Common Hydrates?
For this week: Decompose sodium hydrogen carbonate in a modified Solway process, calculating percent yield and percent atom economy.
References:
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