Humboldt State University ® Department of Chemistry

Richard A. Paselk

Science 331 - Fall 2004

Section 2

"Chemistry" Final Study Guide

Review Quiz 1 Study Guide. Expect 50% of Final to be material from Quiz 1.

Review web notes, examples etc. You are responsible for the materials in your text pp 1-76 (but not Sound)

Terms (be able to define/describe): Define/describe: solution, salt, solvent, solute, saturated solution, phase change, boiling, solid, boiling point (bp), heat of vaporization/condensation, melting point (mp), heat of melting/solidification, Arrhenius acid/base model, "empirical" acid/base definition, heating/cooling curve.

Chemical Reactions: Be able to balance simple equations by inspection such as we have done in class. Remember the important considerations of conservation of mass. (see Lecture 7) For chemical equations, conservation of mass means that we must have the same numbers of the same kinds of atoms on both side of the equation.

Be able to predict the products and balance simple fuel oxidation reactions (burning). (e.g. CH₄ + 2 O₂ -> CO₂ + 2 H₂O)

Predict the charges of the ions of the elements in Groups IA, IIA, VIA, and VIIA. Explain why they have these charges (stable octets, have outer electron structure of nearest Noble gas).

Acids & Bases: What are acids? Bases? What are the charecters of acids and bases. Hydrogen ion, proton, hydroxide ion. Define/describe: Arrhenius acid model, Empirical model, hydronium ion (H₃O⁺), strong acid/base (100% dissociated when < 1M), weak acid/base (less than 100% dissociated when < 1M),

• Be able to write equations for the dissociation of acids and bases (e.g. HCl -> H⁺ + Cl^-)
• the reaction of acids and bases (e.g. HCl + NaOH -> H₂O + Na⁺ + Cl^-)

Note that for "organic" acids (acids with carbon) we will see a common element = -COOH, a carbon with two oxygens, one of which has a hydrogen attached. The hydrogen on the oxygen is then the acidic hydrogen. (Alcohol, with a -COH is not acidic.)

pH and pH scale (Fig 1.20, p 32 in text)

• Note that acids have low pH (< 7), bases high pH (>7) and neutral solutions have a pH of 7 (in reality a range of pH values near 7 are generally considered neutral).

The History of the Earth and Deep Time:

How old is the Earth? How long ago did the precambrian end? What marks the end of the precambrian and the beginning of the currrent Eon? (The modern fossil record of multicellular animals with hard parts began with the Cambrian.) What are some of the major occurances in the Precambrian?

What usually happens to mark the end of a major geological period (e.g. the end of the Cambrian, or the Cretaceous).

Note that Precambrian occurances are listed in notes and Phanerozoic times are summarised on HSU NHM exhibits website.

How do we know how old things are?

Look at three different age systems:

Universe

1. Stellar Life Cycle: Stars burn hydrogen at particular rates depending on how big (bright) they are. Oldest globular clusters stars with ages between 11 By and 18 By.
2. Hubble Constant: Universe is "expanding." That is all galaxies are going away. If calculate how long it has been since they were in same place, then Universe 12-14 By old by recent calculations.
3. WMAP Satellite: Measures of microwave background pattern, etc. Calculations give an age of 13.7 By ±1%.

Earth and Solar System

1. Rock layers. Layers in sedimentary rock generally will be seasonal, like tree rings. Again can extend range by looking for overlaps. Determined Earth must be 100's of millions of years old in nineteenth century.
   • Different biological organisms are characteristic of each time period-determine relationships of deposits by comparing organisms.
2. Glacial Ice. Count layers, like in tree rings (below). Very deep ice-fields go back over 200,000 years.
3. Radiometric dating. Depends on rate of decay of radioisotopes. For ancient time use long half-life isotopes such as ²³⁸U.

Archeology

1. Tree rings. Note that can go past oldest living tree if older wood which overlaps is available (e.g. in old buildings, preserved in bogs, at archeological sites). Limited to about 10,000 y so far.
2. Radiometric dating. Depends on rate of decay of radioisotopes. For "recent" times use short half-life isotopes such as ¹⁴C.

Be able to determine age of sample given amount decayed and half-life as done in class (Lecture 11).

Rates of Chemical Reactions

How are chemicasl reaction rates effected by temperature? concentration? Explain why each relationship should be true.

Gases

Gases are characterized by four properties

1. Amount of substance, n  (in moles)
2. Volume, V (in Liters)
3. Pressure, P (in atm, though often measured in mmHg)
4. Temperature (in K)

Describe/define Bolye's Law and Charles Law. How does gas volume change with pressure? with temperature?

How did the study of gases result in the concept of "absolute zero"?

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© R A Paselk

Last modified 6 December 2004