Last modified: Wed 12/31/1969 06:00:00 pm BCE

Oklahoma State University

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Answer all of the questions below. If you do not know an answer enter CNA. However, it will help me the most if you answer each question with your best intuition/idea about what would be a reasonable answer.

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1. Complete the following table for this compound.


Symbol of Central Atom(s) (CA)

Symbol of Terminal Atom(s)

# of valence electrons on a C atom

# of valence electrons on a Cl atom

total # of valence electrons on CCl4


2. The Lewis structure that we drew for CCl4 is shown below,

In the image the covalent bonds between carbon and chlorine are depicted as lines and the lone pair electrons on chlorine are depicted as red circles, where each circle symbolizes an electron. Given this information answer the following questions.

a) How many electrons are represented by the line (covalent bond) between each carbon - chlorine atom?


b) How many nonbonding electrons are on each chlorine atom?


c) How many covalent bonds does the carbon atom have?


d) How many covalent bonds does each chlorine atom?


3. Formal charge is number that can be calculated for each atom in a Lewis structure. For any atom in a Lewis structure the formal charge can be calculated using the following equation;

Atom's Formal Charge (FC) = # valence electrons on the atom - 0.5 * bonding electrons on the atom - # of nonbonding electrons on the atom

As an example in the Lewis structure for CCl4 above, we can use the formal charge equation to determine the formal charge on the carbon atom and on all of the chlorine atoms.

For C in CCl4:

C has 4 valence electrons, 8 bonding electrons and 0 nonbonding electrons.

FC (C) = 4 – 0.5*8 – 0 = 0

For Cl in CCl4:

Cl has 7 valence electrons, 2 bonding electrons and 6 nonbonding electrons.

FC (Cl) = 7 – 0.5*2 – 6 = 0

Based on these calculations the formal charge on carbon in CCl4 is 0 and the formal charge on each chlorine atom in CCl4 is also 0.

4. Below is the Lewis structure for chloroform, CHCl3.

Complete the following table:


Formal Charge on C

Formal Charge on H

Formal Charge on Cl


5. Draw your own Lewis structure for ClO3- and complete the table below;


Formal Charge on Cl

Formal Charge on O


Answer the following questions using bond energies (this page will open in a new window, resize it so you can see the BCE page) or Table 8.4 on page 330:

6. How much energy (kJ mol-1) is required to break,

H-H bond in H2?

Cl-Cl bond in Cl2?

H-Cl bond in HCl?

7. How much energy (kJ mol-1) is released when forming,

H-H bond in H2?

Cl-Cl bond in Cl2?

H-Cl bond in HCl?

8. Write the chemical equation describing the formation reaction for HCl(g).

9. How much energy is required to break the bonds in the reactants in the above formation equation?

kJ mol-1

10. How much energy is released when forming the bonds in the products in the above formation reaction?

kJ mol-1

11. What is H˚ for the formation reaction?

kJ mol-1


12. Is there anything about the questions that you feel you do not understand? List your concerns/questions.

13. If there is one question you would like to have answered in lecture, what would that question be?