Write the Chemical Symbols for Three Different Atoms or Atomic Cations With 26 Electrons
Problem 1
For each of these Lewis symbols, indicate the group in the periodic table in which the element $\mathrm{X}$ belongs: [Section 8.1$]$
$$(\mathbf{a}) \cdot \dot{\chi} \cdot \quad(\mathbf{b}) \cdot \mathbf{X} \cdot \quad(\mathbf{c}) : \dot{\chi}$$
KC
Kevin C.
Numerade Educator
Problem 2
Illustrated are four ions $-\mathrm{A}, \mathrm{B}, \mathrm{X},$ and $\mathrm{Y}-$ showing their relative ionic radii. The ions shown in red carry positive charges: a $2+$ charge for A and a $1+$ charge for B. Ions shown in blue carry negative charges: a $1-$ charge for $\mathrm{X}$ and a $2-$ charge for $\mathrm{Y}$ . (a) Which combinations of these ions produce ionic compounds where there is a $1 : 1$ ratio of cations and anions? (b) Among the combinations in part (a), which leads to the ionic compound having the largest lattice energy? $[$ Section 8.2$]$
ME
Matthew E.
Numerade Educator
Problem 3
A portion of a two-dimensional "slab" of NaCl(s) is shown here (see Figure 8.2$)$ in which the ions are numbered. (a) Which colored balls must represent sodium ions? (b) Which colored balls must represent chloride ions? (c) Consider ion $5 .$ How many attractive electrostatic interactions are shown for it? (\boldsymbol{d} ) ~ C o n s i d e r ~ i o n ~ $5 .$ How many repulsive interactions are shown for it? (e) Is the sum of the attractive interactions in part (c) larger or smaller than the sum of the repulsive interactions in part (d)? (f) If this pattern of ions was extended indefinitely in two dimensions, would the
lattice energy be positive or negative? [ Section 8.2$]$
Madi S.
Numerade Educator
Problem 4
The orbital diagram that follows shows the valence electrons for a $2+$ ion of an element. (a) What is the element? (b) What is the electron configuration of an atom of this element? [ Section 8.2$]$
ME
Matthew E.
Numerade Educator
Problem 5
In the Lewis structure shown here, $A, D, E, Q, X,$ and $Z$ represent elements in the first two rows of the periodic table. Identify all six elements so that the formal charges of all atoms are zero. [ Section 8.3$]$
Christopher N.
Numerade Educator
Problem 6
Incomplete Lewis structures for the nitrous acid molecule, $\mathrm{HNO}_{2},$ and the nitrite ion, $\mathrm{NO}_{2}^{-},$ are shown here. (a) Complete each Lewis structure by adding electron pairs as needed. (b) Is the formal charge on $\mathrm{N}$ the same or different in these two species? (c) Would either $\mathrm{HNO}_{2}$ or $\mathrm{NO}_{2}^{-}$ be expected to exhibit resonance? (d) Would you expect the $\mathrm{N}=\mathrm{O}$ bond in $\mathrm{HNO}_{2}$ to be longer, shorter, or the same length as the $\mathrm{N}-\mathrm{O}$ bonds in $\mathrm{NO}_{2}^{-}$ ? [Sections 8.5 and 8.6$]$
$$\mathrm{H}-\mathrm{O}-\mathrm{N}=\mathrm{O} \quad \mathrm{O}-\mathrm{N}=\mathrm{O}$$
James I.
Numerade Educator
Problem 7
The partial Lewis structure that follows is for a hydrocarbon molecule. In the full Lewis structure, each carbon atom satisfies the octet rule, and there are no unshared electron pairs in the molecule. The carbon-carbon bonds are labeled $1,2,$ and $3 .$ (a) How many hydrogen atoms are in the molecule? (b) Rank the carbon-carbon bonds in order of increasing bond length. (c) Which carbon-carbon bond is the strongest one? [Sections 8.3 and 8.8]
$$\mathrm{C}^{\underline{1}} \mathrm{C}^{\underline{2}} \mathrm{C} \stackrel{3}{\equiv} \mathrm{C}$$
Lori M.
Numerade Educator
Problem 8
Consider the Lewis structure for the polyatomic oxyanion shown here, where $X$ is an element from the third period $($ Na $-$ Ar). By changing the overall charge, $n,$ from $1-$ to $2-$ to $3-$ we get three different polyatomic ions. For each of these ions (a) identify the central atom, $\mathrm{X} ;(\mathbf{b})$ determine the formal charge of the central atom, $\mathrm{X} ;(\mathbf{c})$ draw a Lewis structure that makes the formal charge on the central atom equal to zero. [Sections $8.5,8.6,$ and 8.7$]$
James I.
Numerade Educator
Problem 9
(a) True or false: An element's number of valence electrons is the same as its atomic number. (b) How many valence electrons does a nitrogen atom possess? (c) An atom has the electron configuration 1$s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{2}$ . How many valence electrons does the atom have?
KC
Kevin C.
Numerade Educator
Problem 10
(a) True or false: The hydrogen atom is most stable when it has a full octet of electrons. (b) How many electrons must a sulfur atom gain to achieve an octet in its valence shell? (c) If an atom has the electron configuration $1 s^{2} 2 s^{2} 2 p^{3},$ how many electrons must it gain to achieve an octet?
James I.
Numerade Educator
Problem 11
Consider the element silicon, Si. (a) Write its electron configuration. (b) How many valence electrons does a silicon atom have? (c) Which subshells hold the valence electrons?
Christopher N.
Numerade Educator
Problem 12
(a) Write the electron configuration for the element titanium, Ti. How many valence electrons does this atom possess? (b) Hafnium, Hf, is also found in group 4 $\mathrm{B}$ . Write the electron configuration for Hf. (c) Ti and Hf behave as though they possess the same number of valence electrons. Which of the subshells in the electron configuration of $\mathrm{Hf}$ behave as valence orbitals? Which behave as
core orbitals?
James I.
Numerade Educator
Problem 13
Write the Lewis symbol for atoms of each of the following elements: (a) Al, (b) Br, (c) Ar, (d) Sr.
KC
Kevin C.
Numerade Educator
Problem 14
What is the Lewis symbol for each of the following atoms or ions? (a) $\mathrm{K},$ (b) As, (c) $\mathrm{Sn}^{2+},(\mathbf{d}) \mathrm{N}^{3-}$ .
James I.
Numerade Educator
Problem 15
(a) Using Lewis symbols, diagram the reaction between magnesium and oxygen atoms to give the ionic substance MgO. (b) How many electrons are transferred? (c) Which atom loses electrons in the reaction?
KC
Kevin C.
Numerade Educator
Problem 16
(a) Use Lewis symbols to represent the reaction that occurs between Ca and F atoms. (b) What is the chemical formula of the most likely product? (c) How many electrons are transferred? ( $\mathbf{d} )$ Which atom loses electrons in the reaction?
James I.
Numerade Educator
Problem 17
Predict the chemical formula of the ionic compound formed between the following pairs of elements: (a) Al and F, (b) K and $S,(\mathbf{c}) \mathrm{Y}$ and $\mathrm{O},(\mathbf{d}) \mathrm{Mg}$ and $\mathrm{N} .$
KC
Kevin C.
Numerade Educator
Problem 18
Which ionic compound is expected to form from combining the following pairs of elements? (a) barium and fluorine, (b) cesium and chlorine, (c) lithium and nitrogen, (d) aluminum and oxygen.
James I.
Numerade Educator
Problem 19
Write the electron configuration for each of the following ions, and determine which ones possess noble-gas configurations: (a) $\mathrm{Sr}^{2+},(\mathbf{b}) \mathrm{Ti}^{2+},(\mathbf{c}) \mathrm{Se}^{2-},(\mathbf{d}) \mathrm{Ni}^{2+},(\mathbf{e}) \mathrm{Br}^{-}$ $(\mathbf{f}) \mathrm{Mn}^{3+}$
KC
Kevin C.
Numerade Educator
Problem 20
Write electron configurations for the following ions, and determine which have noble-gas configurations: (a) $\mathrm{Cd}^{2+}$ , $(\mathbf{b}) \mathrm{P}^{3-},(\mathbf{c}) \mathrm{Zr}^{4+},(\mathbf{d}) \mathrm{Ru}^{3+},(\mathbf{e}) \mathrm{As}^{3-},(\mathbf{f}) \mathrm{Ag}^{+}$
James I.
Numerade Educator
Problem 21
(a) Is lattice energy usually endothermic or exothermic? (b) Write the chemical equation that represents the process of lattice energy for the case of NaCl. (c) Would you expect salts like NaCl, which have singly charged ions, to have larger or smaller lattice energies compared to salts like CaO which are composed of doubly-charged ions?
Ronald P.
Numerade Educator
Problem 22
NaCl and KF have the same crystal structure. The only difference between the two is the distance that separates cations and anions. (a) The lattice energies of NaCl and KF are given in Table $8.1 .$ Based on the lattice energies, would you expect the Na $-$ Cl or the $\mathrm{K}-$ F distance to be longer? (b) Use the ionic radii given in Figure 7.8 to estimate the $\mathrm{Na}-\mathrm{Cl}$ and $\mathrm{K}-\mathrm{F}$ distances.
James I.
Numerade Educator
Problem 23
The substances $\mathrm{NaF}$ and $\mathrm{CaO}$ are isoelectronic (have the same number of valence electrons). (a) What are the charges on each of the cations in each compound? (b) What are the
charges of each of the anions in each compound? (c) Without looking up lattice energies, which compound is predicted to have the larger lattice energy? (d) Using the lattice energies in Table $8.1,$ predict the lattice energy of ScN.
KC
Kevin C.
Numerade Educator
Problem 24
(a) Does the lattice energy of an ionic solid increase or decrease (i) as the charges of the ions increase, (ii) as the sizes of the ions increase? (b) Arrange the following substances not listed in Table 8.1 according to their expected lattice energies, listing them from lowest lattice energy to the highest: MgS, Ki, GaN, LiBr.
James I.
Numerade Educator
Problem 25
Consider the ionic compounds KF, NaCl, NaBr, and LiCl. (a) Use ionic radil (Figure 7.8) to estimate the cation-anion distance for each compound. (b) Based on your answer to part (a), arrange these four compounds in order of decreasing lattice energy. (c) Check your predictions in part (b) with the experimental values of lattice energy from Table $8.1 .$ Are the predictions from ionic radii correct?
Ronald P.
Numerade Educator
Problem 26
Which of the following trends in lattice energy is due to differences in ionic radii? (a) $\mathrm{NaCl} > \mathrm{RbBr} > \mathrm{CsBr}$ (b) $\mathrm{BaO} > \mathrm{KF},(\mathbf{c}) \mathrm{SrO} > \mathrm{SrCl}_{2}$
James I.
Numerade Educator
Problem 27
Energy is required to remove two electrons from Ca to form $\mathrm{Ca}^{2+},$ and energy is required to add two electrons to $\mathrm{O}$ to form $\mathrm{O}^{2-} .$ Yet $\mathrm{CaO}$ is stable relative to the free elements. Which statement is the best explanation? (a) The lattice energy of CaO is large enough to overcome these processes. (b) CaO is a covalent compound, and these processes are
irrelevant. (c) CaO has a higher molar mass than either Ca or O. (d) The enthalpy of formation of CaO is small. (e) CaO is stable to atmospheric conditions.
TT
Tracy T.
Numerade Educator
Problem 28
List the individual steps used in constructing a Born-Haber cycle for the formation of $\mathrm{Bal}_{2}$ from the elements. Which of the steps would you expect to be exothermic?
James I.
Numerade Educator
Problem 29
Use data from Appendix C, Figure 7.10 , and Figure 7.12 to calculate the lattice energy of RbCl.
Ronald P.
Numerade Educator
Problem 30
(a) Based on the lattice energies of MgCl_ and SrCl_ given in Table $8.1,$ what is the range of values that you would expect for the lattice energy of $\mathrm{CaCl}_{2} ?$ (b) Using data from Appendix C, Figure $7.11,$ Figure $7.13,$ and the value of the second ionization energy for $\mathrm{Ca}, 1145 \mathrm{kJ} / \mathrm{mol},$ calculate the lattice energy of $\mathrm{CaCl}_{2} .$
James I.
Numerade Educator
Problem 31
(a) State whether or not the bonding in each substance is likely to be covalent: (i) iron, (ii) sodium chloride, (iii) water, (iv) oxygen, (v) argon. (b) A substance XY, formed from two different elements, boils at $-33^{\circ} \mathrm{C}$ . Is XY likely to be a covalent or an ionic substance?
KC
Kevin C.
Numerade Educator
Problem 32
Which of these elements are unlikely to form covalent bonds? S, H, K, Ar, Si.
James I.
Numerade Educator
Problem 33
Using Lewis symbols and Lewis structures, diagram the formation of SiCl, from Si and Cl atoms, showing valencshell electrons. (a) How many valence electrons does Si have ini initially? (c) How many valence electrons surround the Si in the SiCl_ molecule? (d) How many valence electrons surround each Clin the SiCl_ molecule? (e) How many bonding pairs of electrons are in the SiCl_ $_{4}$ molecule?
Ronald P.
Numerade Educator
Problem 34
Use Lewis symbols and Lewis structures to diagram the formation of $\mathrm{PF}_{3}$ from $\mathrm{P}$ and $\mathrm{F}$ atoms, showing valence-shell electrons. (a) How many valence electrons does P have initially? (b) How many valence electrons does each F have initially? ( c) How many valence electrons surround the Pin the PF_ $_{3}$ molecule? (d) How many valence electrons surround each $\mathrm{F}$ in the $\mathrm{PF}_{3}$ molecule? (e) How many bonding pairs of
electrons are in the $\mathrm{PF}_{3}$ molecule?
ME
Matthew E.
Numerade Educator
Problem 35
(a) Construct a Lewis structure for $\mathrm{O}_{2}$ in which each atom achieves an octet of electrons. (b) How many bonding electrons are in the structure? (c) Would you expect the $\mathrm{O}-\mathrm{O}$ bond in $\mathrm{O}_{2}$ to be shorter or longer than the $\mathrm{O}-\mathrm{O}$
bond in compounds that contain an $\mathrm{O}-\mathrm{O}$ single bond? Explain.
KC
Kevin C.
Numerade Educator
Problem 36
(a) Construct a Lewis structure for hydrogen peroxide, $\mathrm{H}_{2} \mathrm{O}_{2}$ in which each atom achieves an octet of electrons. (b) How many bonding electrons are between the two oxygen atoms? (c) Do you expect the $\mathrm{O}-\mathrm{O}$ bond in $\mathrm{H}_{2} \mathrm{O}_{2}$ to be longer or shorter than the $\mathrm{O}-\mathrm{O}$ bond in $\mathrm{O}_{2} ?$ Explain.
James I.
Numerade Educator
Problem 37
Which of the following statements about electronegativity is false? (a) Electronegativity is the ability of an atom in a molecule to attract electron density toward itself. (b) Electronegativity is the same thing as electron affinity. (c) The numerical values for electronegativity have no units. (d) Fluorine is the most
electronegative element. (e) Cesium is the least electronegative element.
Ronald P.
Numerade Educator
Problem 38
(a) What is the trend in electronegativity going from left to right in a row of the periodic table? (b) How do
electronegativity values generally vary going down a column in the periodic table? (c) True or false: The most easily ionizable elements are the most electronegative.
James I.
Numerade Educator
Problem 39
Using only the periodic table as your guide, select the most electronegative atom in each of the following sets: (a) Na, $\mathrm{Mg}, \mathrm{K}, \mathrm{Ca} ;(\mathbf{b}) \mathrm{P}, \mathrm{S},$ As, $\mathrm{Se} ;(\mathbf{c}) \mathrm{Be}, \mathrm{B}, \mathrm{C}, \mathrm{Si} ;(\mathbf{d}) \mathrm{Zn}, \mathrm{Ge}, \mathrm{Ga}, \mathrm{Gs}$
KC
Kevin C.
Numerade Educator
Problem 40
By referring only to the periodic table, select (a) the most electronegative element in group $6 \mathrm{A} ;(\mathbf{b})$ the least electronegative element in the group Al, Si, P; (c) the most electronegative element in the group $\mathrm{Ga}, \mathrm{P}, \mathrm{Cl}, \mathrm{Na} ;(\mathbf{d})$ the element in the group $\mathrm{K}$ $\mathrm{C}, \mathrm{Zn}, \mathrm{F}$ that is most likely to form an ionic compound with Ba.
James I.
Numerade Educator
Problem 41
Which of the following bonds are polar? (a) $\mathrm{B}-\mathrm{F}$ (b) Cl-Cl, (c) Se-O, (d) H-I. Which is the more electronegative atom in each polar bond?
KC
Kevin C.
Numerade Educator
Problem 42
Arrange the bonds in each of the following sets in order of increasing polarity: (a) $\mathrm{C}-\mathrm{F}, \mathrm{O}-\mathrm{F}, \mathrm{Be}-\mathrm{F}$ ;
(b) $\mathrm{O}-\mathrm{Cl}, \mathrm{S}-\mathrm{Br}, \mathrm{C}-\mathrm{P} ;(\mathbf{c}) \mathrm{C}-\mathrm{S}, \mathrm{B}-\mathrm{F}, \mathrm{N}-\mathrm{O}$
James I.
Numerade Educator
Problem 43
(a) From the data in Table $8.2,$ calculate the effective charges on the $\mathrm{H}$ and $\mathrm{Br}$ atoms of the HBr molecule in units of the electronic charge, $e$ (b) If you were to put HBr under very high pressure, so its bond length decreased significantly, would its dipole moment increase, decrease, or stay the same, if you assume that the effective charges on the atoms do not change?
Ronald P.
Numerade Educator
Problem 44
The iodine monobromide molecule, IBr, has a bond length of 2.49 and a dipole moment of 1.21 $\mathrm{D}$ (a) Which atom of the molecule is expected to have a negative charge? (b) Calculate the effective charges on the I and Br atoms in IBr in units of the electronic charge, $e$ .
James I.
Numerade Educator
Problem 45
In the following pairs of binary compounds, determine which one is a molecular substance and which one is an ionic substance. Use the appropriate naming convention (for ionic or molecular substances) to assign a name to each compound: (a) $\mathrm{SiF}_{4}$ and $\mathrm{LaF}_{3},(\mathbf{b}) \mathrm{FeCl}_{2}$ and $\mathrm{ReCl}_{6},(\mathrm{c}) \mathrm{PbCl}_{4}$
and $\mathrm{RbCl} .$
KC
Kevin C.
Numerade Educator
Problem 46
In the following pairs of binary compounds, determine which one is a molecular substance and which one is an ionic substance. Use the appropriate naming convention (for ionic or molecular substances) to assign a name to each compound: (a) $\mathrm{TiCl}_{4}$ and $\mathrm{CaF}_{2},(\mathbf{b}) \mathrm{ClF}_{3}$ and $\mathrm{VF}_{3},(\mathbf{c}) \mathrm{SbCl}_{5}$ and $\mathrm{AlF}_{3} .$
James I.
Numerade Educator
Problem 47
Draw Lewis structures for the following: (a) $\operatorname{SiH}_{4},$ (b) $\mathrm{CO}$ $(\mathbf{c}) \mathrm{SF}_{2},(\mathbf{d}) \mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{H}$ is bonded to $\mathrm{O})$ , $(\mathbf{e}) \mathrm{ClO}_{2}^{-},(\mathbf{f}) \mathrm{NH}_{2} \mathrm{OH}$
KC
Kevin C.
Numerade Educator
Problem 48
Write Lewis structures for the following: (a) $\mathrm{H}_{2} \mathrm{CO}$ (both $\mathrm{H}$ atoms are bonded to $\mathrm{C} ),(\mathbf{b}) \mathrm{H}_{2} \mathrm{O}_{2},(\mathbf{c}) \mathrm{C}_{2} \mathrm{F}_{6}$ (contains $\mathrm{a} \mathrm{C}-\mathrm{C}$ bond), $(\mathbf{d}) \mathrm{AsO}_{3}^{3-},$ (e) $\mathrm{H}_{2} \mathrm{SO}_{3}(\mathrm{H}$ is bonded to $\mathrm{O})$ $(\mathbf{f}) \mathrm{NH}_{2} \mathrm{Cl}$
James I.
Numerade Educator
Problem 49
Which one of these statements about formal charge is true? (a) Formal charge is the same as oxidation number. (b) To draw the best Lewis structure, you should minimize formal charge. (c) Formal charge takes into account the different electronegativities of the atoms in a molecule. (d) Formal charge is most useful for ionic compounds. (e) Formal charge is used in calculating the dipole moment of a diatomic
molecule.
KC
Kevin C.
Numerade Educator
Problem 50
(a) Draw the dominant Lewis structure for the phosphorus trifluoride molecule, PF $_{3}$ . (b) Determine the oxidation numbers of the $P$ and $F$ atoms. (c) Determine the formal charges of the $P$ and $F$ atoms.
James I.
Numerade Educator
Problem 51
Write Lewis structures that obey the octet rule for each of the following, and assign oxidation numbers and formal charges to each atom: (a) OCS, (b) SOCl_ $_{2}(S$ is the central atom), $(\mathbf{c}) \mathrm{BrO}_{3}^{-},(\mathbf{d}) \mathrm{HClO}_{2}(\mathrm{H}$ is bonded to O)
Madi S.
Numerade Educator
Problem 52
For each of the following molecules or ions of sulfur and oxygen, write a single Lewis structure that obeys the octet rule, and calculate the oxidation numbers and formal charges on all the atoms: (a) SO $_{2},(\mathbf{b}) \mathrm{SO}_{3},(\mathrm{c}) \mathrm{SO}_{3}^{2-}$ (d) Arrange these molecules/ions in order of increasing $S-O$ bond length.
James I.
Numerade Educator
Problem 53
(a) Draw the best Lewis structure(s) for the nitrite ion, NO $_{2}^{-}$ (b) With what allotrope of oxygen is it isoelectonic? (c) What would you predict for the lengths of the bonds in $\mathrm{NO}_{2}^{-}$ relative to $\mathrm{N}-\mathrm{O}$ single bonds and double bonds?
KC
Kevin C.
Numerade Educator
Problem 54
Consider the formate ion, $\mathrm{HCO}_{2}^{-},$ which is the anion formed when formic acid loses an $\mathrm{H}^{+}$ ton. The $\mathrm{H}$ and the two O atoms are bonded to the central $\mathrm{C}$ atom. (a) Draw the best Lewis structure(s) for this ion. (b) Are resonance structures needed to describe the structure? (c) Would you predict that the $\mathrm{C}-\mathrm{O}$ bond lengths in the formate ion would be longer or shorter relative to those in $\mathrm{CO}_{2} ?$
James I.
Numerade Educator
Problem 55
Predict the ordering, from shortest to longest, of the bond lengths in $\mathrm{CO}, \mathrm{CO}_{2},$ and $\mathrm{CO}_{3}^{2-}$ .
KC
Kevin C.
Numerade Educator
Problem 56
Based on Lewis structures, predict the ordering, from shortest to longest, of $N-O$ bond lengths in $N O^{+}, N O_{2}^{-},$ and $N O_{3}^{-} .$
ME
Matthew E.
Numerade Educator
Problem 57
True or false: (a) The $\mathrm{C}-$ Cbonds in benzene are all the same length and correspond to typical single $\mathrm{C}-\mathrm{Cbond}$ lengths. (b) The $\mathrm{C}-\mathrm{C}$ bond in acetylene, HCCH, is longer than the average $\mathrm{C}-\mathrm{C}$ bond length in benzene.
KC
Kevin C.
Numerade Educator
Problem 58
Mothballs are composed of naphthalene, $\mathrm{C}_{10} \mathrm{H}_{8},$ a molecule that consists of two six-membered rings of carbon fused along an edge, as shown in this incomplete Lewis structure: (a) Draw all of the resonance structures of naphthalene. How many are there? (b) Do you expect the $C-C$ bond lengths in the molecule to be similar to those of $C-C$ single bonds, $C=C$ double bonds, or intermediate between $\mathrm{C}-\mathrm{C}$ single and $\mathrm{C}=\mathrm{C}$ double bonds? (c) Not all of the $\mathrm{C}-\mathrm{C}$ bond lengths in naphthalene are equivalent. Based on your resonance structures, how many $\mathrm{C}-\mathrm{C}$ bonds in the molecule do you expect to be shorter than the others?
James I.
Numerade Educator
Problem 59
(a) Which of these compounds is an exception to the octet rule: carbon dioxide, water, ammonia, phosphorus trifluoride, or arsenic pentafluoride? (b) Which of these compounds or ions is an exception to the octet rule: borohydride $\left(\mathrm{BH}_{4}^{-}\right),$ borazine $\left(\mathrm{B}_{3} \mathrm{N}_{3} \mathrm{H}_{6},$ which is analogous \right. to benzene with alternating $\mathrm{B}$ and $\mathrm{N}$ in the ring $),$ or boron trichloride?
KC
Kevin C.
Numerade Educator
Problem 60
Fill in the blank with the appropriate numbers for both electrons and bonds (considering that single bonds are counted as one, double bonds as two, and triple bonds as three).
(a) Fluorine has _____ valence electrons and makes______
bond(s) in compounds.
(b) Oxygen has _____ valence electrons and makes ______
bond(s) in compounds.
(c) Nitrogen has _____ valence electrons and makes ______
bond(s) in compounds.
(d) Carbon has _____ valence electrons and makes ______
bond(s) in compounds.
James I.
Numerade Educator
Problem 61
Draw the dominant Lewis structures for these chlorine-oxygen molecules/ions: ClO, ClO $^{-}, \mathrm{ClO}_{2}^{-}, \mathrm{ClO}_{3}^{-}, \mathrm{ClO}_{4}^{-}$ Which of these do not obey the octet rule?
KC
Kevin C.
Numerade Educator
Problem 62
For Group $3 \mathrm{A}-7 \mathrm{A}$ elements in the third row of the periodic table and beyond, the octet rule is often not obeyed. A friend of yours says this is because these heavier elements are more likely to make double or triple bonds. Another friend of yours says that this is because the heavier elements are larger and can make bonds to more than four atoms at a time. Which friend is more correct?
James I.
Numerade Educator
Problem 63
Draw the Lewis structures for each of the following ions or molecules. Identify those in which the octet rule is not obeyed; state which atom in each compound does not follow the octet rule; and state, for those atoms, how many electrons surround these atoms: (a) $\mathrm{PH}_{3},$ (b) AlH_ $_{3},(\mathbf{c}) \mathrm{N}_{3}^{-}$ (d) $\mathrm{CH}_{2} \mathrm{Cl}_{2},(\mathbf{e}) \mathrm{SnF}_{6}^{2-}$
KC
Kevin C.
Numerade Educator
Problem 64
Draw the Lewis structures for each of the following molecules or ions. Identify instances where the octet rule is not obeyed; state which atom in each compound does not follow the octet rule; and state how many electrons surround these atoms: (a) $\mathrm{NO},(\mathbf{b}) \mathrm{BF}_{3},(\mathbf{c}) \mathrm{ICl}_{2}^{-},(\mathbf{d}) \mathrm{OPBr}_{3}($ the $\mathrm{P}$ is the central atom), (e) XeF.
James I.
Numerade Educator
Problem 65
In the vapor phase, $\mathrm{BeCl}_{2}$ exists as a discrete molecule. (a) Draw the Lewis structure of this molecule, using only single bonds. Does this Lewis structure satisfy the octet rule? (b) What other resonance structures are possible that satisfy the octet rule? (c) On the basis of the formal charges, which Lewis structure is expected to be dominant for BeCl_ $_{2} ?$
KC
Kevin C.
Numerade Educator
Problem 66
(a) Describe the molecule xenon trioxide, $\mathrm{XeO}_{3},$ using four possible Lewis structures, one each with zero, one, two, or three $\mathrm{Xe}-\mathrm{O}$ double bonds. (b) Do any of these resonance structures satisfy the octet rule for every atom in the molecule? (c) Do any of the four Lewis structures have multiple resonance structures? If so, how many resonance structures do you find? (d) Which of the Lewis structures in part (a) yields the most favorable formal charges for the molecule?
Problem 67
There are many Lewis structures you could draw for sulfuric acid, $\mathrm{H}_{2} \mathrm{SO}_{4}$ (each $\mathrm{H}$ is bonded to an O). (a) What Lewis structure(s) would you draw to satisfy the octet rule? (b) What Lewis structure(s) would you draw to minimize formal charge?
KC
Kevin C.
Numerade Educator
Problem 68
Some chemists believe that satisfaction of the octet rule should be the top criterion for choosing the dominant Lewis structure of a molecule or ion. Other chemists believe that achieving the best formal charges should be the top criterion. Consider the dihydrogen phosphate ion, $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$ , in which the $\mathrm{H}$ atoms are bonded to $\mathrm{O}$ atoms. (a) What is the predicted dominant Lewis structure if satisfying the octet rule is the top criterion? (b) What is the predicted dominant Lewis structure if achieving the best formal charges is the top criterion?
James I.
Numerade Educator
Problem 69
Using Table 8.3 , estimate $\Delta H$ for each of the following gas-phase reactions (note that lone pairs on atoms are not shown):
Madi S.
Numerade Educator
Problem 70
Using Table $8.3,$ estimate $\Delta H$ for the following gas-phase reactions:
James I.
Numerade Educator
Problem 71
State whether each of these statements is true or false. (a) The longer the bond, the larger the bond enthalpy. (b) $C-C$ bonds are stronger than $C-H$ bonds. (c) A typical single bond length is in the $5-10$ Ä range. (d) If you break a chemical bond, energy is released.(e) Energy is stored in chemical bonds.
KC
Kevin C.
Numerade Educator
Problem 72
State whether each of these statements is true or false. (a) A carbon-carbon triple bond is shorter than a carbon-carbon single bond. (b) There are exactly six bonding electrons in the $\mathrm{O}_{2}$ molecule. (c) The $\mathrm{C}-\mathrm{O}$ bond in carbon monoxide is longer than the $\mathrm{C}-\mathrm{O}$ bond in carbon dioxide. (d) The O $-\mathrm{O}$ bond in ozone is shorter than the $\mathrm{O}-$ O bond in $\mathrm{O}_{2}$ . (e) The more electronegative the atom, the more bonds it makes to other atoms.
ME
Matthew E.
Numerade Educator
Problem 73
We can define average bond enthalpies and bond lengths for ionic bonds, just like we have for covalent bonds. Which ionic bond is predicted to be stronger, $\mathrm{Na}-\mathrm{Cl}$ or $\mathrm{Ca}-\mathrm{O}$ ?
KC
Kevin C.
Numerade Educator
Problem 74
We can define average bond enthalpies and bond lengths for ionic bonds, just like we have for covalent bonds. Which ionic bond is predicted to have the smaller bond enthalpy, Li-F or $\mathrm{Cs}-\mathrm{F}$ ?
James I.
Numerade Educator
Problem 75
A carbene is a compound that has a carbon bonded to two atoms and a lone pair remaining on the carbon. Many carbenes are very reactive. (a) Draw the Lewis structure for the simplest carbene, $\mathrm{H}_{2} \mathrm{C}$ . ( b) Predict the length of the carbon-carbon bond you would expect if two $\mathrm{H}_{2} \mathrm{C}$ molecules reacted with each other by a combination reaction.
KC
Kevin C.
Numerade Educator
Problem 76
Draw the Lewis structure for $\mathrm{NO}^{+} .$ Is the nitrogen-oxygen bond in $\mathrm{NO}^{+}$ longer, shorter, or the same length as the nitrogen-oxygen bond in NO? Explain.
James I.
Numerade Educator
Problem 77
A new compound is made that has a $\mathrm{C}-\mathrm{C}$ bond length of 1.15 $\mathrm{A} .$ Is this bond likely to be a single, double, or triple $\mathrm{C}-\mathrm{Cbond} ?$
KC
Kevin C.
Numerade Educator
Problem 78
A new compound is made that has an $\mathrm{N}-\mathrm{N}$ bond length of 1.26 A. Is this bond likely to be a single, double, or triple $\mathrm{C}-\mathrm{C}$ bond?
James I.
Numerade Educator
Problem 79
Consider the lattice energies of the following Group 2 $\mathrm{A}$ compounds: $\mathrm{Be} \mathrm{H}_{2}, 3205 \mathrm{kJ} / \mathrm{mol} ; \mathrm{MgH}_{2}, 2791 \mathrm{kJ} / \mathrm{mol}$ $\mathrm{CaH}_{2}, 2410 \mathrm{kJ} / \mathrm{mol} ; \mathrm{SrH}_{2}, 2250 \mathrm{kJ} / \mathrm{mol} ; \mathrm{BaH}_{2}, 2121 \mathrm{kJ} / \mathrm{mol}$
(a) What is the oxidation number of $\mathrm{H}$ in these compounds? (b) Assuming that all of these compounds have the same three-dimensional arrangement of ions in the solid, which of these compounds has the shortest cation-anion distance? (c) Consider BeH $_{2} .$ Does it require 3205 kJ of energy to break one mole of the solid into its ions, or does breaking up one mole of solid into its ions release 3205 $\mathrm{kJ}$ of energy? (d) The lattice energy of $\mathrm{ZnH}_{2}$ is 2870 $\mathrm{kJ} / \mathrm{mol}$ . Considering the trend in lattice enthalpies in the Group 2 $\mathrm{A}$ compounds, predict which Group 2 $\mathrm{A}$ element is most similar in ionic radius to the $\mathrm{Zn}^{2+}$ ion.
Madi S.
Numerade Educator
Problem 80
Based on data in Table 8.1, estimate (within 30 $\mathrm{kJ} / \mathrm{mol}$ ) the lattice energy for (a) LiBr, $(\mathbf{b})$ CsBr, $(\mathbf{c}) \mathrm{CaCl}_{2}$
James I.
Numerade Educator
Problem 81
An ionic substance of formula MX has a lattice energy of $6 \times 10^{3} \mathrm{k} / \mathrm{mol} .$ Is the charge on the ion M likely to be $1+, 2+,$ or $3+?$ Explain.
KC
Kevin C.
Numerade Educator
Problem 82
The ionic compound CaO crystallizes with the same structure as sodium chloride (Figure 8.3$)$ . (a) In this structure, how many $\mathrm{O}^{2-}$ are in contact with each $\mathrm{Ca}^{2+}$ ion (Hint: Remember the pattern of ions shown in Figure 8.3 repeats over and over again in all three directions.) (b) Would energy be consumed or released if a crystal of CaO was converted to a collection of widely separated $\mathrm{Ca}-\mathrm{O}$ ion pairs? (c) From the ionic radii given in Figure 7.8 , calculate the potential energy of a single Ca-O ion pair that is just touching (the magnitude of electronic charge is given on the inside back cover).(d) Calculate the energy of a mole of such pairs. How does this compare to the lattice energy of $\mathrm{CaO}$ ? (e) What factor do you think accounts for most of the discrepancy between the energies in part (d)- the bonding in CaO is more covalent than ionic, or the electrostatic interactions in a crystal lattice are more complicated than those in a single ion pair?
James I.
Numerade Educator
Problem 83
Construct a Born-Haber cycle for the formation of the hypothetical compound NaCl , where the sodium ion has a $2+$ charge (the second ionization energy for sodium is given in Table 7.2 . (a) How large would the lattice energy need to be for the formation of $\mathrm{NaCl}_{2}$ to be exothermic? (b) If we were to estimate the lattice energy of $\mathrm{NaCl}_{2}$ to be roughly equal to that of $\mathrm{MgCl}_{2}(2326 \mathrm{kJ} / \mathrm{mol}$ from Table 8.1$),$ what value would you obtain for the standard enthalpy of formation, $\Delta H_{f}^{\circ},$ of $\mathrm{NaCl}_{2} ?$
Problem 84
A classmate of yours is convinced that he knows everything about electronegativity. (a) In the case of atoms $X$ and $Y$ having different electronegativities, he says, the diatomic molecule $X-Y$ must be polar. Is your classmate correct? (b) Your classmate says that the farther the two atoms are apart in a
bond, the larger the dipole moment will be. Is your classmate correct?
James I.
Numerade Educator
Problem 85
Consider the collection of nonmetallic elements $\mathrm{O}, \mathrm{P}$ , Te, $\mathrm{I},$ and $\mathrm{B} .$ (a) Which two would form the most polar single bond? (b) Which two would form the longest single bond? (c) Which two would be likely to form a compound of formula $\mathrm{XY}_{2} ?(\mathbf{d})$ Which combinations of elements would likely yield a compound of empirical formula $\mathrm{X}_{2} \mathrm{Y}_{3}$ ?
KC
Kevin C.
Numerade Educator
Problem 86
The substance chlorine monoxide, ClO(g), is important in atmospheric processes that lead to depletion of the ozone layer. The ClO molecule has an experimental dipole moment of $1.24 \mathrm{D},$ and the $\mathrm{Cl}-$ O bond length is 1.60 $\mathrm{A}$ . (a) Determine the magnitude of the charges on the Cl and O atoms in units of the electronic charge, $e$ (b) Based on the electronegativities of the elements, which atom would you expect to have a partial negative charge in the Clo molecule? (c) Using formal charges as a guide, propose the dominant Lewis structure for the molecule. (d) The anion $\mathrm{ClO}^{-}$ exists. What is the formal charge on the Cl for the best Lewis structure for $\mathrm{ClO}^{-}$ ?
Christopher N.
Numerade Educator
Problem 87
(a) Using the electronegativities of Br and Cl, estimate the partial charges on the atoms in the Br-Cl molecule. (b) Using these partial charges and the atomic radii given in Figure 7.8 , estimate the dipole moment of the molecule. (c) The measured dipole moment of BrCl is 0.57 $\mathrm{D}$ . If you assume the bond length in BrCl is the sum of the atomic radii, what are the partial charges on the atoms in BrCl using the experimental dipole moment?
Rashmi S.
Numerade Educator
Problem 88
A major challenge in implementing the "hydrogen economy" is finding a safe, lightweight, and compact way of storing hydrogen for use as a fuel. The hydrides of light metals are attractive for hydrogen storage because they can store a high weight percentage of hydrogen in a small volume. For example, NaAlH_ can release 5.6$\%$ of its mass as $\mathrm{H}_{2}$ upon decomposing to $\operatorname{NaH}(s), \operatorname{Al}(s),$ and $\mathrm{H}_{2}(g) .$ NaAlH_ possesses both covalent bonds, which hold polyatomic anions together, and ionic bonds. (a) Write a balanced equation for the decomposition of NaAlH_.. (b) Which element in NaAlH_ is the most electronegative? Which one is the least electronegative? (c) Based on electronegativity differences, predict the identity of the polyatomic anion. Draw a Lewis structure for this ion. (d) What is the formal charge on hydrogen in the polyatomic ion?
James I.
Numerade Educator
Problem 89
Although $\mathrm{I}_{3}$ is a known ion, $\mathrm{F}_{3}^{-}$ is not. (a) Draw the Lewis structure for $\mathrm{I}_{3}^{-}$ (it is linear, not a triangle). (b) One of your classmates says that $\mathrm{F}_{3}^{-}$ does not exist because $\mathrm{Fis}$ too electronegative to make bonds with another atom. Give an example that proves your classmate is wrong. (c) Another classmate says $\mathrm{F}_{3}^{-}$ does not exist because it would violate the octet rule. Is this classmate possibly correct? (d) Yet another classmate says $\mathrm{F}_{3}^{-}$ does not exist because $\mathrm{F}$ is too small to make bonds to more than one atom. Is this classmate possibly correct?
Problem 90
Calculate the formal charge on the indicated atom in each of the following molecules or ions: (a) the central oxygen atom in $\mathrm{O}_{3},$ (b) phosphorus in $\mathrm{PF}_{6}^{-},(\mathbf{c})$ nitrogen in $\mathrm{NO}_{2}$ (d) iodine in ICl_$\mathrm{ICl}_{3},$ (e) chlorine in $\mathrm{HClO}_{4}$ (hydrogen is bonded to $\mathrm{O} )$
James I.
Numerade Educator
Problem 91
The hypochlorite ion, $\mathrm{ClO}^{-},$ is the active ingredient in bleach. The perchlorate ion, $\mathrm{ClO}_{4}^{-},$ is a main component of rocket propellants. Draw Lewis structures for both ions (a) What is the formal charge of Cl in the hypochlorite ion? (b) What is the formal charge of Cl in the perchlorate ion, assuming the Cl-O bonds are all single bonds? (c) What is the oxidation number of Cl in the hypochlorite ion? (d) What is the oxidation number of $C l$ in the perchlorate ion, assuming the $C l-O$ bonds are all single bonds? (e) In a redox reaction, which ion would you expect to be more easily reduced?
Problem 92
The following three Lewis structures can be drawn for $\mathrm{N}_{2} \mathrm{O} :$ (a) Using formal charges, which of these three resonance forms is likely to be the most important? (b) The N-N bond length in $\mathrm{N}_{2} \mathrm{O}$ is $1.12 \mathrm{A},$ slightly longer than a typical $\mathrm{N}=\mathrm{N}$ bond; and the $\mathrm{N}-\mathrm{O}$ bond length is $1.19 \mathrm{A},$ slightly shorter than a typical $\mathrm{N}=\mathrm{O}$ bond (see Table 8.4$) .$ Based on these data, which resonance structure best represents $\mathrm{N}_{2} \mathrm{O} ?$
James I.
Numerade Educator
Problem 93
(a) Triazine, $\mathrm{C}_{3} \mathrm{H}_{3} \mathrm{N}_{3},$ is like benzene except that in triazine every other $\mathrm{C}-\mathrm{H}$ group is replaced by a nitrogen atom. Draw the Lewis structure(s) for the triazine molecule. (b) Estimate the carbon-nitrogen bond distances in the ring.
KC
Kevin C.
Numerade Educator
Problem 94
Ortho-Dichlorobenzene, $\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{Cl}_{2},$ is obtained when two of
the adjacent hydrogen atoms in benzene are replaced with Cl atoms. A skeleton of the molecule is shown here. (a) Complete a Lewis structure for the molecule using bonds and electron pairs as needed. (b) Are there any resonance structures for the molecule? If so, sketch them. (c) Are the resonance structures in (a) and (b) equivalent to one another as they are in benzene?
James I.
Numerade Educator
Problem 95
Consider the hypothetical molecule $\mathrm{B}-\mathrm{A}=\mathrm{B}$ . Are the following statements true or false? (a) This molecule cannot exist. (b) If resonance was important, the molecule would have identical $A-B$ bond lengths.
KC
Kevin C.
Numerade Educator
Problem 96
An important reaction for the conversion of natural gas to other useful hydrocarbons is the conversion of methane to ethane.
$$2 \mathrm{CH}_{4}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g)+\mathrm{H}_{2}(g)$$
In practice, this reaction is carried out in the presence of oxygen, which converts the hydrogen produced into water.
$$2 \mathrm{CH}_{4}(g)+\frac{1}{2} \mathrm{O}_{2}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g)+\mathrm{H}_{2} \mathrm{O}(g)$$
Use Table 8.3 to estimate $\Delta H$ for these two reactions. Why is the conversion of methane to ethane more favorable when oxygen is used?
James I.
Numerade Educator
Problem 97
Two compounds are isomers if they have the same chemical formula but different arrangements of atoms. Use Table 8.3 to estimate $\Delta H$ for each of the following gas-phase isomerization reactions and indicate which isomer has the lower enthalpy.
Ronald P.
Numerade Educator
Problem 98
The Ti $\mathrm{Ti}^{2+}$ ion is isoelectronic with the Ca atom. (a) Write the electron configurations of $\mathrm{Ti}^{2+}$ and (b) Calculate the number of unpaired electrons for Ca and for $\mathrm{Ti}^{2+} .$ (c) What charge would Ti have to be isoelectronic with $\mathrm{Ca}^{2}+?$
James I.
Numerade Educator
Problem 99
(a) Draw the Lewis structure for hydrogen peroxide, $\mathrm{H}_{2} \mathrm{O}_{2}$ . (b) What is the weakest bond in hydrogen peroxide? (c) Hydrogen peroxide is sold commercially as an aqueous solution in brown bottles to protect it from light. Calculate the longest wavelength of light that has sufficient energy to break the weakest bond in hydrogen peroxide.
KC
Kevin C.
Numerade Educator
Problem 100
The electron affinity of oxygen is $-141 \mathrm{kJ} / \mathrm{mol},$ corresponding to the reaction
$$\mathrm{O}(g)+e^{-} \longrightarrow \mathrm{O}^{-}(g)$$
The lattice energy of $\mathrm{K}_{2} \mathrm{O}(s)$ is 2238 $\mathrm{kJ} / \mathrm{mol}$ . Use these data along with data in Appendix $\mathrm{C}$ and Figure 7.10 to calculate the "second electron affinity" of oxygen, corresponding to the reaction
$$\mathrm{O}^{-}(g)+e^{-} \longrightarrow \mathrm{O}^{2}(g)$$
James I.
Numerade Educator
Problem 101
You and a partner are asked to complete a lab entitled "Oxides of Ruthenium" that is scheduled to extend over two lab periods. The first lab, which is to be completed by your partner, is devoted to carrying out compositional analysis. In the second lab, you are to determine melting points. Upon going to lab you find two unlabeled vials, one containing a soft yellow substance and the other a black powder. You
also find the following notes in your partner's notebook Compound $1 : 76.0 \%$ Ru and 24.0$\%$ O (by mass), Compound $2 : 61.2 \%$ Ru and 38.8$\%$ O (by mass). (a) What is the empirical formula for Compound 1$?$ (b) What is the empirical formula for Compound 2$?$ Upon determining the melting points of these two compounds, you find that the yellow compound melts at $25^{\circ} \mathrm{C}$ , while the black powder does not melt up to the maximum temperature of your apparatus, $1200^{\circ} \mathrm{C}$ . (c) What is the identity of the yellow compound? (d) What is the identity of the black compound? (e) Which compound is molecular? (f) Which compound is ionic?
KC
Kevin C.
Numerade Educator
Problem 102
One scale for electronegativity is based on the concept that the electronegativity of any atom is proportional to the ionization energy of the atom minus its electron affinity: electronegativity $=k(I-E A),$ where $k$ is a proportionality constant. (a) How does this definition explain why the electronegativity of $F$ is greater than that of $C 1,$ even though Cl has the greater electron affinity? (b) Why are both ionization energy and electron affinity relevant to the notion of electronegativity? (c) By using data in Chapter 7 , determine the value of $k$ that would lead to an electronegativity of 4.0 for Funder this definition. (d) Use your result from part (c) to determine the electronegativities of $\mathrm{Cl}$ and $\mathrm{O}$ using this scale. (e) Another scale for electronegativity defines electronegativity as the average of an atom's first ionization energy and its electron affinity. Using this scale, calculate the electronegativities for the halogens, and scale them so that fluorine has an electronegativity of $4.0 .$ On this scale, what is Br's electronegativity?
James I.
Numerade Educator
Problem 103
The compound chloral hydrate, known in detective stories as knockout drops, is composed of $14.52 \% \mathrm{C}, 1.83 \% \mathrm{H}$ , $64.30 \% \mathrm{Cl},$ and 13.35$\% \mathrm{O}$ by mass, and has a molar mass of 165.4 $\mathrm{g} / \mathrm{mol}$ . (a) What is the empirical formula of this substance? (b) What is the molecular formula of this substance? (c) Draw the Lewis structure of the molecule, assuming that the Cl atoms bond to a single $C$ atom and that there are a $C-C$ bond and two $C-O$ bonds in the compound.
KC
Kevin C.
Numerade Educator
Problem 104
Barium azide is 62.04$\%$ Ba and 37.96$\%$ N. Each azide ion has a net charge of $1-$ (a) Determine the chemical formula of the azide ion. (b) Write three resonance structures for the azide ion. (c) Which structure is most important? (d) Predict the bond lengths in the ion.
James I.
Numerade Educator
Problem 105
Acetylene $\left(\mathrm{C}_{2} \mathrm{H}_{2}\right)$ and nitrogen $\left(\mathrm{N}_{2}\right)$ both contain a triple bond, but they differ greatly in their chemical properties. (a) Write the Lewis structures for the two substances. (b) By referring to Appendix C, look up the enthalpies of formation of acetylene and nitrogen. Which compound is more stable? (c) Write balanced chemical equations for the complete oxidation of $\mathrm{N}_{2}$ to form $\mathrm{N}_{2} \mathrm{O}_{5}(g)$ and of acetylene to form $\mathrm{CO}_{2}(g)$ and $\mathrm{H}_{2} \mathrm{O}(g) .$ (d) Calculate the enthalpy of oxidation per mole for $\mathrm{N}_{2}$ and for $\mathrm{C}_{2} \mathrm{H}_{2}$ (the enthalpy of formation of $\mathrm{N}_{2} \mathrm{O}_{5}(g)$ is 11.30 $\mathrm{kJ} / \mathrm{mol}$ . (e) Both $\mathrm{N}_{2}$ and $\mathrm{C}_{2} \mathrm{H}_{2}$ possess triple bonds with quite high bond enthalpies (Table 8.3$)$ . Calculate the enthalpy of hydrogenation per mole for both compounds: acetylene plus $\mathrm{H}_{2}$ to make methane, $\mathrm{CH}_{4}$ ;
nitrogen plus $\mathrm{H}_{2}$ to make ammonia, $\mathrm{NH}_{3}$ .
Problem 106
Under special conditions, sulfur reacts with anhydrous liquid ammonia to form a binary compound of sulfur and nitrogen. The compound is found to consist of 69.6$\% \mathrm{S}$ and 30.4$\% \mathrm{N} .$ Measurements of its molecular mass yield a value of 184.3 $\mathrm{g} / \mathrm{mol}$ . The compound occasionally detonates on being struck or when heated rapidly. The sulfur and nitrogen atoms of the molecule are joined in a ring. All the bonds in the ring are of the same length. (a) Calculate the empirical and molecular formulas for the substance. (b) Write Lewis structures for the molecule, based on the information you are given. (Hint: You should find a relatively small number of dominant Lewis structures.) (c) Predict the bond distances between the atoms in the ring. (Note: The $S-S$ distance in the $S_{8}$ ring is 2.05 A.) ( d.) The enthalpy of formation of the compound is estimated to be 480 $\mathrm{kJ} / \mathrm{mol}^{-1} . \Delta H_{f}^{9}$ of $\mathrm{S}(g)$ is 222.8 $\mathrm{kJ} / \mathrm{mol} .$ Estimate the average bond enthalpy in the compound.
James I.
Numerade Educator
Problem 107
A common form of elemental phosphorus is the tetrahedral $\mathrm{P}_{4}$ molecule, where all four phosphorus atoms are equivalent: At room temperature phosphorus is a solid. (a) Are there any lone pairs of electrons in the $\mathrm{P}_{4}$ molecule? (b) How many $\mathrm{p}-\mathrm{p}$ bonds are there in the molecule? (c) Draw a Lewis structure for a linear $P_{4}$ molecule that satisfies the octet rule. Does this molecule have resonance structures? (d) On the basis of formal charges, which is more stable, the linear molecule or the tetrahedral molecule?
Ronald P.
Numerade Educator
Problem 108
Formic acid has the chemical formula HCOOH. It is a colorless liquid that has a density of 1.220 $\mathrm{g} / \mathrm{mL}$ . (a) The carbon atom in formic acid is bound to one $\mathrm{H}$ and both $\mathrm{O}^{\prime}$ 's. Draw the Lewis structure for formic acid, showing resonance if present. (b) Formic acid can react with NaOH in aqueous solution to produce the formate ion, HCOO- . Write the
balanced chemical equation for this reaction. (c) Draw the Lewis structure of the formate ion, showing resonance if present. (d) How many milliliters of a 0.100 M solution of NaOH would it take to completely react with 0.785 $\mathrm{mL}$ of formic acid?
James I.
Numerade Educator
Problem 109
Ammonia reacts with boron trifluoride to form a stable compound, as we saw in Section 8.7 . (a) Draw the Lewis structure of the ammonia-boron trifluoride reaction product. (b) The B-N bond is obviously more polar than the $\mathrm{C}-\mathrm{C}$ bond. Draw the charge distribution you expect on the
$\mathrm{B}-\mathrm{N}$ bond within the molecule (using the delta plus and delta minus symbols mentioned in Section 8.4$)$ . ( ) Boron trichloride also reacts with ammonia in a similar way to
the trifluoride. Predict whether the $B-N$ bond in the trichloride reaction product would be more or less polar than the $B-N$ bond in the trifluoride product, and justify your reasoning.
Madi S.
Numerade Educator
Problem 110
Ammonium chloride, $\mathrm{NH}_{4} \mathrm{Cl},$ is a very soluble salt in water. (a) Draw the Lewis structures of the ammonium and chloride ions. (b) Is there an $\mathrm{N}-$ Cl bond in solid ammonium chloride? (c) If you dissolve 14 gof ammonium chloride in 500.0 $\mathrm{mL}$ of water, what is the molar concentration of the solution? (d) How many grams of silver nitrate do you need to add to the solution in part (c) to precipitate all of the chloride as silver chloride?
James I.
Numerade Educator
Write the Chemical Symbols for Three Different Atoms or Atomic Cations With 26 Electrons
Source: https://www.numerade.com/books/chapter/basic-concepts-of-chemical-bonding/