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22.14.18: Chapter 18

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    452948
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    1.

    The alkali metals all have a single s electron in their outermost shell. In contrast, the alkaline earth metals have a completed s subshell in their outermost shell. In general, the alkali metals react faster and are more reactive than the corresponding alkaline earth metals in the same period.

    3.


    5.

    The possible ways of distinguishing between the two include infrared spectroscopy by comparison of known compounds, a flame test that gives the characteristic yellow color for sodium (strontium has a red flame), or comparison of their solubilities in water. At 20 °C, NaCl dissolves to the extent of compared with for SrCl2. Heating to 100 °C provides an easy test, since the solubility of NaCl is but that of SrCl2 is Density determination on a solid is sometimes difficult, but there is enough difference (2.165 g/mL NaCl and 3.052 g/mL SrCl2) that this method would be viable and perhaps the easiest and least expensive test to perform.

    7.

    (a) (b) (c) (d) (e)

    9.

    11 lb

    11.

    Yes, tin reacts with hydrochloric acid to produce hydrogen gas.

    13.

    In PbCl2, the bonding is ionic, as indicated by its melting point of 501 °C. In PbCl4, the bonding is covalent, as evidenced by it being an unstable liquid at room temperature.

    15.

    17.

    Cathode (reduction): Anode (oxidation): Overall reaction:

    19.

    0.5035 g H2

    21.

    Despite its reactivity, magnesium can be used in construction even when the magnesium is going to come in contact with a flame because a protective oxide coating is formed, preventing gross oxidation. Only if the metal is finely subdivided or present in a thin sheet will a high-intensity flame cause its rapid burning.

    23.

    Extract from ore:
    Recover:
    Sinter:
    Dissolve in Na3AlF6(l) and electrolyze:

    25.

    25.83%

    27.

    39 kg

    29.

    (a) H3BPH3:

    This Lewis structure is composed of a boron atom single bonded to a phosphorus atom. Each of these atoms is single bonded to three hydrogen atoms.

    (b)

    This Lewis structure is composed of a boron atom single bonded to four fluorine atoms, each of which has three lone pairs of electrons. The structure is surrounded by brackets, and a negative sign appears as a superscript outside the brackets.

    (c) BBr3:

    This Lewis structure is composed of a boron atom single bonded to three bromine atoms, each of which has three lone pairs of electrons.

    (d) B(CH3)3:

    This Lewis structure is composed of a boron atom that is single bonded to three carbon atoms, each of which is single bonded to three hydrogen atoms.

    (e) B(OH)3:

    This Lewis structure is composed of a boron atom that is single bonded to three oxygen atoms, each of which has two lone pairs of electrons. Each oxygen atom is single bonded to a hydrogen atom.

    31.

    1s22s22p63s23p23d0.

    33.

    (a) (CH3)3SiH: sp3 bonding about Si; the structure is tetrahedral; (b) sp3 bonding about Si; the structure is tetrahedral; (c) Si2H6: sp3 bonding about each Si; the structure is linear along the Si-Si bond; (d) Si(OH)4: sp3 bonding about Si; the structure is tetrahedral; (e) sp3d2 bonding about Si; the structure is octahedral

    35.

    (a) nonpolar; (b) nonpolar; (c) polar; (d) nonpolar; (e) polar

    37.

    (a) tellurium dioxide or tellurium(IV) oxide; (b) antimony(III) sulfide; (c) germanium(IV) fluoride; (d) silane or silicon(IV) hydride; (e) germanium(IV) hydride

    39.

    Boron has only s and p orbitals available, which can accommodate a maximum of four electron pairs. Unlike silicon, no d orbitals are available in boron.

    41.

    (a) ΔH° = 87 kJ; ΔG° = 44 kJ; (b) ΔH° = −109.9 kJ; ΔG° = −154.7 kJ; (c) ΔH° = −510 kJ; ΔG° = −601.5 kJ

    43.

    A mild solution of hydrofluoric acid would dissolve the silicate and would not harm the diamond.

    45.

    In the N2 molecule, the nitrogen atoms have an σ bond and two π bonds holding the two atoms together. The presence of three strong bonds makes N2 a very stable molecule. Phosphorus is a third-period element, and as such, does not form π bonds efficiently; therefore, it must fulfill its bonding requirement by forming three σ bonds.

    47.

    (a) H = 1+, C = 2+, and N = 3−; (b) O = 2+ and F = 1−; (c) As = 3+ and Cl = 1−

    49.

    S < Cl < O < F

    51.

    The electronegativity of the nonmetals is greater than that of hydrogen. Thus, the negative charge is better represented on the nonmetal, which has the greater tendency to attract electrons in the bond to itself.

    53.

    Hydrogen has only one orbital with which to bond to other atoms. Consequently, only one two-electron bond can form.

    55.

    0.43 g H2

    57.

    (a) (b)
    (c)

    59.

    (a) NH2−:

    This Lewis structure shows a nitrogen atom with three lone pairs of electrons single bonded to a hydrogen atom. The structure is surrounded by brackets. Outside and superscript to the brackets is a two negative sign.

    (b) N2F4:

    This Lewis structure shows two nitrogen atoms, each with one lone pair of electrons, single bonded to one another and each single bonded to two fluorine atoms. Each fluorine atom has three lone pairs of electrons.

    (c)

    This Lewis structure shows a nitrogen atom with two lone pairs of electrons single bonded to two hydrogen atoms. The structure is surrounded by brackets. Outside and superscript to the brackets is a negative sign.

    (d) NF3:

    This Lewis structure shows a nitrogen atom, with one lone pair of electrons, single bonded to three fluorine atoms. Each fluorine atom has three lone pairs of electrons.

    (e)

    Three Lewis structures are shown and connected by double-headed arrows in between. The left structure shows a nitrogen atom with a lone pair of electrons triple bonded to a second nitrogen which is single bonded to a third nitrogen. The third nitrogen has three lone pairs of electrons. The entire structure is surrounded by brackets, and outside and superscript to the brackets is a negative sign. The middle structure shows a nitrogen atom with three lone pair of electrons single bonded to a second nitrogen which is triple bonded to a third nitrogen. The third nitrogen which has one lone pair of electrons. The entire structure is surrounded by brackets, and outside and superscript to the brackets is a negative sign. The right structure shows a nitrogen atom with two lone pairs of electrons double bonded to a second nitrogen which is double bonded to a third nitrogen. The third nitrogen atom has two lone pairs of electrons. The entire structure is surrounded by brackets, and outside and superscript to the brackets is a negative sign.

    61.

    Ammonia acts as a Brønsted base because it readily accepts protons and as a Lewis base in that it has an electron pair to donate.
    Brønsted base:
    Lewis base:

    63.

    (a) NO2:

    Two Lewis structures are shown and connected by double-headed arrows in between. The left structure shows a nitrogen atom with a single electron double bonded to an oxygen atom which has two lone pairs of electrons. The nitrogen atom is also single bonded to an oxygen atom with three lone pairs of electrons. The right structure is a mirror image of the left structure.

    Nitrogen is sp2 hybridized. The molecule has a bent geometry with an ONO bond angle of approximately 120°.
    (b)

    Two Lewis structures are shown and connected by double-headed arrows in between. Each structure is surrounded by brackets, and outside and superscript to the brackets is a negative sign. The left structure shows a nitrogen atom with a lone pair of electrons double bonded to an oxygen atom which has two lone pairs of electrons. The nitrogen atom is also single bonded to an oxygen atom with three lone pair of electrons. The right structure is a mirror image of the left structure.

    Nitrogen is sp2 hybridized. The molecule has a bent geometry with an ONO bond angle slightly less than 120°.
    (c)

    This Lewis structure shows a nitrogen atom double bonded on both sides to an oxygen atom which has two lone pairs of electrons each. The structure is surrounded by brackets and outside and superscript to the brackets is a negative sign.

    Nitrogen is sp hybridized. The molecule has a linear geometry with an ONO bond angle of 180°.

    65.

    Nitrogen cannot form a NF5 molecule because it does not have d orbitals to bond with the additional two fluorine atoms.

    67.

    (a)

    This Lewis structure shows a phosphorus atom with a lone pair of electrons single bonded to three hydrogen atoms.

    (b)

    This Lewis structure shows a phosphorus atom single bonded to four hydrogen atoms. The structure is surrounded by brackets and has a superscript positive sign outside the brackets.

    (c)

    This Lewis structure shows two phosphorus atoms, each with a lone pair of electrons, single bonded to one another. Each phosphorus atom is also single bonded to two hydrogen atoms.

    (d)

    This Lewis structure shows a phosphorus atom single bonded to four oxygen atoms, each with three lone pairs of electrons. The structure is surrounded by brackets and has a superscript 3 negative sign outside the brackets.

    (e)

    This Lewis structure shows a phosphorus atom single bonded to five fluorine atoms, each with three lone pairs of electrons.

    69.

    (a) (b) (c) (d) or (e) or (f)

    71.

    291 mL

    73.

    28 tons

    75.

    (a)

    This Lewis structure shows a phosphorus atom single bonded to four fluorine atoms, each with three lone pairs of electrons. The structure is surrounded by brackets and has a superscript positive sign outside the brackets. The label, “Tetrahedral,” is written under the structure.

    (b)

    This Lewis structure shows a phosphorus atom single bonded to five fluorine atoms, each with three lone pairs of electrons. The label, “Trigonal bipyramidal,” is written under the structure.

    (c)

    A Lewis structure shows a phosphorus atom single bonded to six fluorine atoms, each with three lone pairs of electrons. The structure is surrounded by brackets and has a superscript negative sign outside the brackets. The label, “Octahedral,” is written under the structure.

    (d)

    This Lewis structure shows a phosphorus atom single bonded to three fluorine atoms, each with three lone pairs of electrons. The phosphorus atom is also double bonded to an oxygen atom with two lone pairs of electrons. The label, “Tetrahedral,” is written under the structure.

    77.

    (a) P = 3+; (b) P = 5+; (c) P = 3+; (d) P = 5+; (e) P = 3−; (f) P = 5+

    79.

    FrO2

    81.

    (a) (b) (c) (d)

    83.
    85.

    (a) (b) (c) (d) (e)

    87.

    HClO4 is the stronger acid because, in a series of oxyacids with similar formulas, the higher the electronegativity of the central atom, the stronger is the attraction of the central atom for the electrons of the oxygen(s). The stronger attraction of the oxygen electron results in a stronger attraction of oxygen for the electrons in the O-H bond, making the hydrogen more easily released. The weaker this bond, the stronger the acid.

    89.

    As H2SO4 and H2SeO4 are both oxyacids and their central atoms both have the same oxidation number, the acid strength depends on the relative electronegativity of the central atom. As sulfur is more electronegative than selenium, H2SO4 is the stronger acid.

    91.

    SO2, sp2 4+; SO3, sp2, 6+; H2SO4, sp3, 6+

    93.

    SF6: S = 6+; SO2F2: S = 6+; KHS: S = 2−

    95.

    Sulfur is able to form double bonds only at high temperatures (substantially endothermic conditions), which is not the case for oxygen.

    97.

    There are many possible answers including: and

    99.

    5.1 104 g

    101.

    SnCl4 is not a salt because it is covalently bonded. A salt must have ionic bonds.

    103.

    In oxyacids with similar formulas, the acid strength increases as the electronegativity of the central atom increases. HClO3 is stronger than HBrO3; Cl is more electronegative than Br.

    105.

    (a)

    This Lewis structure shows an iodine atom with one lone pair of electrons single bonded to five fluorine atoms, each of which has three lone pairs of electrons. The image is labeled, “Square pyramidal.”

    (b)

    This Lewis structure shows an iodine atom with three lone pairs of electrons single bonded to two iodine atoms, each of which has three lone pairs of electrons. The image is surrounded by brackets. A superscript negative sign appears outside the brackets. The image is labeled, “Linear.”

    (c)

    This Lewis structure shows a phosphorus atom single bonded to five chlorine atoms, each of which has three lone pairs of electrons. The image is labeled, “Trigonal bipyramidal.”

    (d)

    This Lewis structure shows a selenium atom with one lone pair of electrons single bonded to four fluorine atoms, each of which has three lone pairs of electrons. The image is labeled “Seesaw.”

    (e)

    This Lewis structure shows a chlorine atom with two lone pairs of electrons single bonded to three fluorine atoms, each of which has three lone pairs of electrons. The image is labeled, “T-shaped.”

    107.

    (a) bromine trifluoride; (b) sodium bromate; (c) phosphorus pentabromide; (d) sodium perchlorate; (e) potassium hypochlorite

    109.

    (a) I: 7+; (b) I: 7+; (c) Cl: 4+; (d) I: 3+; Cl: 1−; (e) F: 0

    111.

    (a) sp3d hybridized; (b) sp3d2 hybridized; (c) sp3 hybridized; (d) sp3 hybridized; (e) sp3d2 hybridized;

    113.

    (a) nonpolar; (b) nonpolar; (c) polar; (d) nonpolar; (e) polar

    115.

    The empirical formula is XeF6, and the balanced reactions are:


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