Supplemental Instruction
Iowa State University / Leader: / Grady
Course: / Chem 177
Instructor: / Appy
Date: / 4/10/15
Sections 6.7 – 9.4
1. Write the electron configurations for the following.
a. Se
b. Cr
c. Ni2+
d. Mn4+
2. State the number of valence and core electrons in the following.
a. Ni
b. Be
c. Sn
3. Define, give the periodic trends, and explanations for the trends for the following.
a. Effective nuclear charge
b. Atomic radius
c. Ionization energy
d. Electron affinity
e. Electronegativity
4. Which of the following atoms would these successive values of ionization energies match most likely?
I1 = 578 a) K
I2 =1451 b) Al
I3 = 7733 c) Ca
d) O
e) F
5. Arrange the following in order of increasing size.
a. Se2-,Te2-, Se
b. Co3+, Fe2+, Fe3+
c. Ca, Ti4+, Sc3+
d. Be2+, Na+, Ne
e. Rb+, Sr2+, Se2, Br-?
6. Which element has the smaller first ionization energy?
a. Ti, Ba
b. Ag, Cu
c. Ge, Cl
d. Pb, Sb
7. Describe the nature of the following chemical bonds:
Element / ENAl / 1.6
Mg / 1.3
F / 4.0
N / 3.0
O / 3.5
H / 2.1
Cl / 3.0
Br / 2.8
Mn / 1.8
a. F -- N
b. H -- O
c. Mg – O
d. Cl – Br
e. Fe – O (in Fe)
9. Complete the following chemical reactions
a. Strontium oxide is added to water
b. Cesium is added to water
c. Sulfur trioxide with water
d. Chromium (III) oxide with dilute hydrochloric acid
10. Arrange the following bonds in order of increasing polarity:
a. C—F, O—F, Be—F
b. C—S, B—F, N—O
11. What is the dipole moment of a +2 and -2 charge of atoms that are separated by a distance of 0.97 Angstroms (give answer in Debyes) 1 e- = 1.60x10-19C; 1D=3.34x10-30 C*m; 1 Angstrom = 1x10-10m
12. Calculate the charges on the H and Br atoms of the HBr molecule in units of electronic charge, e, given that μ=0.82 D and r = 1.41 Angstroms.
13. Triple bonds are the ______(strength) and are the ______(length) and have the ______(energy). While single bonds are the ______(strength) and are the ______(length) and have the ______(energy).
14. For each of the following molecules, draw the Lewis structure (include resonance structures if applicable) and determine the formal charges on all atoms. Then arrange these molecules in order of increasing S—O bond distance.
a. SO2
b. NO3-
c. PO33-
15. Draw possible Lewis structures for XeO3 and decide which of these resonance structures yields the most favorable form.
16. Draw Lewis structures for the following molecules. Give their electron and molecular geometries, bond angles, and polarity.
a. AlH3
b. N3-
c. CH2Cl2
d. ICl2-
e. N2O
f. SO3
17. Would you expect N2 or O3 to be more reactive? Why?
18. A substance has the formula AB3 and it is determined that the A— B bond is polar. Is this sufficient information to conclude that AB3 has a molecular dipole? If not, what additional information is needed and why?
19. Estimate the enthalpy for each of the following reaction using bond enthalpies. Is the reaction exothermic or endothermic?
a. 2CH4(g) + O2(g) à 2CH3OH(g)
Bond / dH (kJ/mol)C—H / 413
O=O / 495
C—O / 358
O—H / 463
C—C / 348
C=C / 614
20. Molecule 2-butene,C4H8, see drawing. This molecule can undergo geometric transformations that can be induced by light.
a. Based on bond energies, how much energy per molecule must be supplied to break the C—C pi bond?
b. What is the longest wavelength of light that will provide photons of sufficient energy to break the C—C pi bond?