Answers and Explanations

The correct answer is (C). The orbital diagram in choice (C) shows filled s and p sublevels, which are characteristic of the nonreactive noble gases. 

The correct answer is (A). In choice (A), two electrons in the same orbital have like spins, which is not allowed by the Pauli Exclusion Principle (they must have opposite spins). 

The correct answer is (B). The second electron in the p orbital should go into a different orbital. According to Hund s rule, all orbitals should fill with a single electron (each having like spins) prior to a second electron entering any orbital. 

The correct answer is (D). The only way a single electron could be in an orbital that is of higher energy than an unoccupied orbital is if it is excited. 

The correct answer is (E). Octane is a much larger molecule allowing for a greater number of interactions between the molecules. This attractive force is sufficient to allow octane to remain in the liquid state at higher temperatures. 

2NH4+ + S042- + Ba2+ + 20H - BaS04 + 2NH3 + 2H20 (or NH4+ + OH ). The AP test frequently includes questions with an ammonia solution (what you re dealing with as products in this reaction). Ammonia and water are actually in equilibrium with the ammonium and hydroxide ions. 

2Na + 2H20 — 2Na+ + 20H- + H2. You ve probably seen this reaction at some point. The reactants should tip you off that it has to be a replacement reaction. The displaced hydrogen ions will combine to form hydrogen gas. 

BF3 + NH3 — BF3NH3. In the ammonia molecule there is a nonbonding pair of electrons that can react in a variety of ways. Later in the book, you will learn about complexes that can form with ammonia. In this reaction, boron trifluoride is a molecule that is usually represented with only 6 electrons around the central boron, making it a perfect mate for the ammonia molecule. As tempted as you might be to try to apply a double-replacement strategy here, remember that they are both molecular substances. This suggests another approach a combination reaction. 

H+ + S032 — HS03. A double-replacement reaction (KC1 is soluble). 

Na20 + h2o — 2Na+ + 20H. A very characteristic reaction for metal oxides. Soluble metal oxides (like this one) are known as basic anhydrides because they dissolve in water to form basic solutions. You can also treat it like a double-replacement reaction. 

D—This was determined by bombarding gold foil with alpha particles. 

A—All others, except D, are Lewis bases. D is neither a Lewis acid nor a Lewis base. 

D—Ca(OH)2, NaOH, and Na2C03 are strong electrolytes and should be separated. Cancel all spectator ions (Na+ and OH-). 

C—The hydroxide took some of the iron with it, so Fe2+ will be low. The nitrate is double the potassium because there are two nitrates per iron(II) nitrate instead of one, as in potassium hydroxide. 

E—The basic difference between ideal and real gases. 

D Isotopes are atoms of the same element that have a different mass number because they have a different number of neutrons. 

C By definition, elements cannot be broken down chemically, whole compounds can be broken down chemically. 

A In a voltaic cell, anions will travel through the salt bridge to the anode while cations will travel through the salt bridge to the cathode. 

B Geiger counters are used to detect radioactive emanations. 

C Burettes are used to deliver acids and bases in a titration because of their ability to give precise readings of the acid and base delivered. 

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Study Guide and Solutions Manual, by Susan McMurry, provides answers and explanations to all in-text and end-of-chapter exercises. (0-495-11268-2)... 

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