9.10 The kinetic energy of molecules is often used to induce
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Chapter 9 Solutions
Chemistry for Engineering Students
- Best Lewis Formula and Molecular Geometry A student writes the Lewis electron-dot formula for the carbonate anion, CO32, as a Does this Lewis formula obey the octet rule? Explain. What are the formal charges on the atoms? Try describing the bonding for this formula in valence bond terms. Do you have any difficulty doing this? b Does this Lewis formula give a reasonable description of the electron structure, or is there a better one? If there is a better Lewis formula, write it down and explain why it is better. c The same student writes the following resonance description for CO2: Is there something wrong with this description? (What would you predict as the geometries of these formulas?) d Is one or the other formula a better description? Could a value for the dipole moment help you decide? e Can you write a Lewis formula that gives an even better description of CO2? Explain your answer.arrow_forwardBond Enthalpy When atoms of the hypothetical element X are placed together, they rapidly undergo reaction to form the X2 molecule: X(g)+X(g)X2(g) a Would you predict that this reaction is exothermic or endothermic? Explain. b Is the bond enthalpy of X2 a positive or a negative quantity? Why? c Suppose H for the reaction is 500 kJ/mol. Estimate the bond enthalpy of the X2 molecule. d Another hypothetical molecular compound, Y2(g), has a bond enthalpy of 750 kJ/mol, and the molecular compound XY(g) has a bond enthalpy of 1500 kJ/mol. Using bond enthalpy information, calculate H for the following reaction. X2(g)+Y2(g)2XY(g) e Given the following information, as well as the information previously presented, predict whether or not the hypothetical ionic compound AX is likely to form. In this compound, A forms the A+ cation, and X forms the X anion. Be sure to justify your answer. Reaction: A(g)+12X2(g)AX(s)The first ionization energy of A(g) is 400 kJ/mol. The electron affinity of X(g) is 525 kJ/mol. The lattice energy of AX(s) is 100 kJ/mol. f If you predicted that no ionic compound would form from the reaction in Part e, what minimum amount of AX(s) lattice energy might lead to compound formation?arrow_forwarda Carbonyl fluoride, COF2, is an extremely poisonous gas used in organofluorine synthesis. Give the valence bond description of the carbonyl fluoride molecule. (Both fluorine atoms are attached to the carbon atom.) b Nitrogen, N2, makes up about 80% of the earths atmosphere. Give the valence bond description of this molecule.arrow_forward
- Acetic acid has the structure CH3CO(OH), in which the OH group is bonded to a C atom. The two carbonoxygen bonds have different lengths. When an acetic acid molecule loses the H from the OH group to form the acetate ion, the two carbonoxygen bonds become equal in length. Explain.arrow_forwardA variety of chlorine oxide fluorides and related cations and anions are known. They tend to be powerful oxidizing and fluorinating agents. FClO3 is the most stable of this group of compounds and has been studied as an oxidizing component in rocket propellants. Draw a Lewis structure for F3ClO, F2ClO2+, and F3ClO2. What is the molecular structure for each species, and what is the expected hybridization of the central chlorine atom in each compound or ion?arrow_forwardAmong the following, which has the shortest bond and which has the longest: Li2, B2, C2, N2, O2?arrow_forward
- The molecular structure shown is of one form of glucose, C6H12O6 Glucose can be oxidized to carbon dioxide and water according to the equation C6H12O6(S) + 6 O2(g)6 CO2(g) + 6 H2O(g) (a) Using the method described in Section 6-6a for estimating enthalpy changes from bond energies, estimate rH for the oxidation of this form of glucose. Make a list of all bonds broken and all bonds formed in this process. (b) Compare your result with the experimental value of 2816 kJ/mol for combustion of glucose. Why might there be a difference between this value and the one you calculated in part (a)?arrow_forwardThe molecules BF3, CF4, CO2, PF5, and SF6 are all nonpolar, even though they all contain polar bonds. Why?arrow_forwardThe molecule shown here. 2-furylmelhanethiol, is responsible for the aroma of coffee: (a) What are the formal charges on the S and O atoms? (b) Give approximate values of angles 1, 2, and 3. (c) Which are the shorter carbon-carbon bonds in the molecule? (d) Which bond in this molecule is the most polar? (e) Is the molecule polar or nonpolar? (f) The four C atoms of the ring are all in a plane. Is the O atom in that same plane (making the five-member ring planar), or is the O atom bent above or below the plane?arrow_forward
- The oxygen oxygen bond in O2 is 112 pm and in O2 is 121 pm. Explain why the bond length in O2+ is shorter than in O2. Would you expect the bond length in O2 to be longer or shorter than that in O2? Why?arrow_forwardConsider the following molecules: SiH4, PH3, H2S. In each case, a central atom is surrounded by four electron pairs. In which of these molecules would you expect the bond angle to be less than 109.5? Explain your reasoning.arrow_forwardIt is possible to write a simple Lewis structure for the SO42- ion, involving only single bonds, which follows the octet rule. However, Linus Pauling and others have suggested an alternative structure, involving double bonds, in which the sulfur atom is surrounded by six electron pairs. (a) Draw the two Lewis structures. (b) What geometries are predicted for the two structures? (c) What is the hybridization of sulfur in each case? (d) What are the formal charges of the atoms in the two structures?arrow_forward
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