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The final exam questions for a college-level chemistry course, focusing on topics such as melting points, electronegativity, molecular geometry, lewis structures, and intermolecular forces. Students are required to answer questions about arranging substances, identifying molecular geometries and hybridization, drawing lewis structures, and explaining concepts related to intermolecular forces.
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Fall 1999 1) Arrange the following substances in order of increasing melting point. Explain your answer. (7 points) LiBr, LiCl, LiF, and CaS 2) Given the following electronegativity information, arrange the three covalent bonds in order of increasing polarity and indicate the “direction” of the polarity. ( points) Element Electronegativity C 2. F 4. Cl 3. I 2.
3) Answer the following questions concerning the compound below. (3 points each)
a) What is the molecular geometry about central atom 4? b) What is the molecular geometry about central atom 7? c) What is the hybridization at central atom 2? d) What is the molecular geometry about central atom 6? e) What is the approximate H-N-H bond angle for central atom 4? f) What is the molecular geometry about central atom 3? g) What is the hybridization at central atom 5? h) What is the molecular geometry about central atom 2? i) How many sigma bonds are represented in the structure above? j) What is the formal charge on central atom 6? k) What is the approximate O-C-O bond angle for central atom 2?
d) XeO 3 MG Hybridization 5) Arrange the following in order of increasing boiling point and assign to each the type of intermolecular force it exhibits. (8 points) He, NH 3 , Ne, and CH 4
2- that minimizes formal charges. (4 points) a) What is the formal charge on the sulfur? (2 points) b) What is the approximate O-S-O bond angle? (2 points)
7) Match the term in column A to the one term or statement in column B that best describes it. Notice that there will be four definitions from column B that will not be used. (1 point each)
T-shaped 1) Weak attraction toward a magnetic field Resonance 2) Weak repulsion by a magnetic field Paramagnetism 3) A notation for the electron configuration of a molecule. Diamagnetism 4) The force of attraction between oppositely charged ions of an ionic compound is directly proportional to their charges and inversely proportional to the square of the distance between them. Valence Electrons 5) Molecular geometry of a molecule or polyatomic ion that has three atoms bonded to a central atom and two unshared pairs on the central atom. Coulomb’s Law 6) Two sigma () bonds Seesaw 7) One sigma () bond and one pi () bond Double Bond 8) One sigma () bond and two pi () bonds Triple Bond 9) One pi () bond and two sigma () bonds Lewis Structure 10) Electron filling sequence 11) Molecular geometry of a molecule or polyatomic ion that has four atoms bonded to a central atom and one unshared pair on the central atom. 12) Electrons in the outermost shell of an atom. 13) A concept in which two or more Lewis formulas are needed to describe the bonding in a molecule or ion. 14) Half the number of electrons in bonding orbitals minus half the number of electrons in antibonding orbitals. 8) Briefly explain why BF 3 is nonpolar while NF 3 is polar. (4 points)
5) Write balanced formula unit AND net ionic equations for reactions that occur when the following compounds are mixed. Be sure to include the physical state of all reactants and products. (4 points each) a) AgNO 3 (aq) + NaCl(aq) b) K 2 CO 3 (aq) + Ca(NO 3 ) 2 (aq) c) HCl(aq) + NaOH(aq) 6) Answer the following questions about a photon of wavelength 412 nm. a) What is the energy of this photon (in J)? (3 points) b) What is the frequency of this photon (in Hz)? (3 points) 7) Which of the following atoms has the largest first ionization energy. (4 points) Na, Al, P, and S
8) Which of the following ions has largest ionic radius. (4 points) K+, S2-, Ca2+, and Cl- 9) Balance this chemical reaction (2 points) and use the balanced reaction to answer the following questions. (6 points) H 2 SO 4 (aq) + KOH(aq) K 2 SO 4 (aq) + H 2 O (l) a) How many grams of K 2 SO 4 (aq) can be produced by reaction of 24.0 g of H 2 SO 4 (aq) and excess KOH(aq)? [Assume 100% yield] 10) A 5.50 L vessel contains Ne at a pressure of 1.12 atm at 24.5^0 C. What mass of Ne is in this vessel assuming ideal gas behavior? (6 points) R = 0.08207 L atm/(K mol)
