L07 Chem 151 Lecture Notes - Lecture 6: Ion Exchange, Reducing Agent, Redox

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harlequinimpala978

13 Dec 2016

School

WUSTL

Department

University College - Chemistry

Course

L07 Chem 151

Professor

Redden

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Document Summary

5 october 2015: the oxidation number is a book-keeping device for the number of electrons gained or. The lowest possible o. n. is -1 and the highest possible is +7, but the most common/stable o. n. are -1, 0, +5, +7. Redox reactions: basics, how do we know if electron transfer has occurred, (ion exchange rxn) 2ag+1n+5o-2, (redox rxn) 2ag+1n+5o-2, in the first reaction, the oxidation states for each element do not change, but in the. 3 + cu0 -> 2 ag0 + cu+2(n+5o-2. 3)2 redox reaction there is a transfer of electrons: for (b), oxidation half reaction: cu0 -> cu2+ + 2e- Cu0 is the reducing agent b/c it is oxidized (loses electrons: reduction half reaction: 2ag+ + 2e- -> 2ag0. Ag+ is the oxidizing agent because it is reduced (gained electrons: both half reactions occur together and simultaneously, must balance the number of electrons lost by the reducing agent with the electrons gained by the oxidizing agent.

Related Questions

Oxidation states are important for keeping track of electrons in oxidation-reduction reactions. Here are some general rules to remember:

In most cases, oxygen has an oxidation state of ?2.
Group 1 and group 2 elements on the periodic table have +1 and +2 oxidation states, respectively.
In most cases, hydrogen has an oxidation state of +1.
Many elements can have more than one oxidation state. In such cases, use the other elements in the compound whose oxidation states are known to determine the oxidation state of the element that varies.

Neutral compounds

In a neutral compound, the sum of the oxidation states is zero. Note that the sign of the oxidation states and the number of atoms associated with each oxidation state must be considered. In H2O, for example, each hydrogen atom has an oxidation state of +1 and each oxygen atom has an oxidation state of ?2 for a total of 2(+1)+(?2)=0.

Part A

What is the oxidation state of an individual carbon atom in CaCO3?

Express the oxidation state numerically (e.g., +1).

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Part B

What is the oxidation state of an individual nitrogen atom in HNO3?

Express the oxidation state numerically (e.g., +1).

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Ions

In an ion, the sum of the oxidation states is equal to the overall ionic charge. Note that the sign of the oxidation states and the number of atoms associated with each oxidation state must be considered. In OH?, for example, the oxygen atom has an oxidation state of ?2 and the hydrogen atom has an oxidation state of +1, for a total of (?2)+(+1)=?1.

Part C

What is the oxidation state of an individual sulfur atom in SO32??

Express the oxidation state numerically (e.g., +1).

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Part D

What is the oxidation state of each individual carbon atom in C2O42??

Express the oxidation state numerically (e.g., +1).

Predict the charge that an aluminum ion would have.