PHYS 1090: Fundamentals of the Physical Universe

University of Wyoming

Unit 13: Reactions
Due Wednesday, December 2, 2009
20 points

This homework should be submitted as a hard copy, on actual paper.

Answer one of the following:

1. Logarithms.

Explain logarithms and why they are used in the pH scale to describe how acidic or basic an aqueous solution is.

2. Acid/base definitions.

I have claimed that the Lewis definition of acids and bases includes the Bronsted-Lowry definition, which includes the Arrhenius definition, as illustrated schematically by this Venn diagram.



Defend that classification. Explain how the Arrhenius definition is contained within the Bronsted-Lowry and Lewis definitions, and how the Bronsted-Lowry definition is contained within the Lewis definition.

3. Chemistry’s irreducible minimum.

Noted chemistry textbook author Peter W. Atkins has stated that there are several concepts that make up the heart of chemistry. We are not quite finished with the class, so we have not covered all of his points yet, but we have explored quite a few of them. Eight of his concepts are listed below.

1. All matter consists of atoms.
2. Atomic structure accounts for the periodic behavior of elements, as manifest in the columns and rows of the periodic table.
3. Bonds between atoms form by electron pair-sharing.
4. Molecular shape is of paramount importance to the behavior of the compound.
5. There are residual forces between molecules beyond covalent bonding.
6. Energy is conserved.
7. Energy and matter tend to disperse.
8. There are barriers to chemical reactions.

Pick four of these concepts. For each of your four, describe one activity or lesson we did in this class to address that concept.

4. Decomposition of H₂O₂.

Hydrogen peroxide (H₂O₂, connected as H–O–O–H) can decompose to form oxygen gas (O₂) and water (H₂O) by the reaction

2 H₂O₂ → O₂ + 2 H₂O.

Write dot structures for every molecule in this reaction and track each atom from the starting materials to the products. For each atom, indicate if it is oxidized, reduced, or neither in the reaction.

5. Pure oxygen.

Explain, using chemical principles we have learned in this class, why the wood and the steel wool burned so much more vigorously in pure oxygen than in air.

6. Additional examples.

In lab, we did just a few examples of redox reactions. Identify two redox reactions in addition to the ones done in lab. Provide balanced equations for the reactions if you can, identify the materials that are oxidized and reduced, and give some background, in a paragraph or so, about each reaction.

Submit your homework in hard copy. Please do not submit it electronically! I plan to sit comfortably at home while reading your homework. I do not intend to be trapped in front of my computer.