Chemistry E-1ax Assignments: Week 10
Reading: Chapter 9 – Chemical Bonding I
For your Discussion Section in Blackboard Collaborate at 5 pm EST on Sunday 11/9:
Look over the Practice Problems pp. 48–52 and be prepared to do those problems.
For next week:
Complete this problem set and email a scanned pdf to Joann Kim ([email protected])
before 6:00pm EST on Thursday 11/13.
Problem Set 8
1. For each of the following polyatomic ions, provide a Lewis structure, including resonance if
appropriate and all non-zero formal charges.
a) BH4–
b) HCO2–
c) AsCl4–
d) ICl2–
(Note: H is bonded to C)
2. For each of the following molecules, provide a Lewis structure, including formal charge and resonance.
Using the table of bond enthalpies from page 314 of your text, along with the following information,
estimate ∆H°f for each of these molecules in the gas phase at 25°C.
ΔH°f (C(g)) = +717 kJ/mol
a) CH3OH (methanol)
b) COCl2 (phosgene) (Note: C is the central atom.)
c) H2NOH (hydroxylamine)
d) N2O4 (bonded like O2N–NO2)
3. a) On the basis of electronegativity, predict whether the molecule ICl (iodine chloride) will be polar.
If it should be polar, which end is positive and which end is negative?
b) Draw a Lewis structure for the molecule CO, including formal charge. It turns out that, in the CO
molecule, the carbon is the negative end of the molecule. Is this what you would expect based on
electronegativity? What could explain this?
c) Draw a Lewis structure for the molecule O3, including formal charge and resonance. Based on
electronegativity differences, would you expect the O–O bonds in ozone to be polar? It turns out
that these bonds are polar; what could explain this?
4.
Construct a Born-Haber cycle and calculate the lattice energy of CaC2 (s). Note that this solid
contains the diatomic ion C22–.
Useful Information: ∆H°f (CaC2(s))
= –60 kJ/mol
∆Hsub (Ca (s))
= +178 kJ/mol
∆Hsub (C (s))
= +717 kJ/mol
Bond dissociation energy of C2 (g)
= +614 kJ/mol
First ionization energy of Ca (g)
= +590 kJ/mol
Second ionization energy of Ca (g)
= +1143 kJ/mol
First electron affinity of C2 (g)
= –315 kJ/mol
Second electron affinity of C2 (g)
= +410 kJ/mol