CDO AP Chemistry Unit 6 Problem Set

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1. Do metals gain or lose electrons in order to acquire a full octet?

2. What charge do group 2A elements acquire as ions?

3. What charge do groups 7A elements acquire as ions?

4. Is energy released or absorbed when individual gaseous ions bond together to form an ionic solid?

5. Which compound in each set will have the strongest ionic bond? Justify your answer (Think Coulombs Law). a. NaCl or KBr

b. NaCl or MgS

c. BeF2 or LiF

d. CaO or CaCl2

e. MgO or Al2O3

f. MgCl2 or MgI2

CDO AP Chemistry Unit 6 Problem Set

6. Which bond from each set is most ionic? Explain (Think Electronegativity). a. Al - O or Na - O

b. K - Cl or Zn - Cl

c. Fr - F or B – F

7. Which compound from each set is most ionic?

a. Al2O3 or NaCl

b. KCl or FeO

8. Which compound from each set is held together by covalent bonds?

a. CO or LiF

b. ZnS or SO2

c. BF3 or Fe2O3

9. Which bond from each set is most covalent? Explain ((Think Electronegativity)

a. Cl – Cl or Al – F

b. N – O or C – O

c. Ca – O or N – O

CDO AP Chemistry Unit 6 Problem Set

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10. Draw Lewis structure for the following compounds and ions. a. CO2

b. NF3

c. O3

d. NH4+

e. NO3

-

f. SO3

CDO AP Chemistry Unit 6 Problem Set

g. POCl3

h. PCl4+

i. H2O

j. HCN

k. Cl2 ( no central atom, make sure octets for both atoms are full)

l. O2 ( no central atom, make sure octets for both atoms are full)

CDO AP Chemistry Unit 6 Problem Set

m. N2 ( no central atom, make sure octets for both atoms are full) Screencast 6-3

11. Calculate the formal charge on each atom of O3.

12. There are two possible structures for CO2. One has two double bonds, and the other has a single and a triple bond. a. Find the formal charge on every atom in each structure.

b. Select the most likely structure. Justify your choice.

CDO AP Chemistry Unit 6 Problem Set

13. There are three possible structures for the cyanate ion (NCO-). Carbon is the least electronegative, so it is always in the center. The different structures result from the placement and choice of multiple bonds (double or triple). a. Find the formal charge on every atom in each structure.

b. Which structure is most likely to occur in nature? Justify your answer.

14. Why can Xenon expand its octet to form compounds, but neon cannot?

15. Draw Lewis structures for the following compounds.

a. SeCl4

b. BCl3

c. PF5

CDO AP Chemistry Unit 6 Problem Set

d. BrF3

e. IF4-

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16. Using only the information given in the thermochemical equation below, make a comparison between the sum of the bond enthalpies of the reactants and the sum of the bond enthalpies of the products. Explain why one value is greater than the other.

CH4(g) + 2O2(g) CO2(g) + 2H2O(g) Hrxn = -802.3 KJ

CDO AP Chemistry Unit 6 Problem Set

Bond Average Bond Enthalpy (KJ/mol)

O – C 351

O = C 799

O – O 142

O = O 499

N – N 193

N = N 418

N = N 941

H – H 436

H – N 393

H - O 467

17. Determine the enthalpy change, Hrxn, that occurs when two gaseous oxygen atoms combine to form a gaseous oxygen molecule (2O(g) O2(g)) from the table of bond enthalpies.

18. Use the chemical equation below and the table of average bond enthalpies to answer the

following questions.

N2(g) + 3H2(g) 2NH3(g)

a. Draw Lewis structures for all three species represented in the reaction above.

b. Calculate the enthalpy change,Hrxn that occurs in the reaction.

CDO AP Chemistry Unit 6 Problem Set

19. Use the thermochemical equation for the combustion of methane below and the tables of average bond energies to find the average bond energy in a C – H bond.

CH4(g) + 2O2(g) CO2(g) + 2H2O(g) Hrxn = -802.3 KJ

20. Rank the following single bond in order of increasing bond length: (Do not use a bond length table) O – C, O – N, O – O, and O – F.

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21. Which bond from each set has the highest bond energy (Do not use a bond energy table to answer this question)? a. N – O or N – F

b. B – F or B – Cl

c. B – C or O – F

d. C – O or C = O

CDO AP Chemistry Unit 6 Problem Set

e. P – Br or P – Cl

22. Which bond from each set is the longest? a. N – O or N = O

b. B – N or B – F

c. Si – O or Si – I

d. C – Cl or C – F

23. C2H2 has a triple bond between the two carbon atoms, and C2H4 has a double bond between

the two carbon atoms. a. Which structure has the shortest C – C bond length? b. Which structure has the greatest C – C bond energy?

c. Provide an explanation for your answer to parts a) and b) using principles of chemical bonding.

CDO AP Chemistry Unit 6 Problem Set

24. This question deals with bonds in carbon dioxide and carbon disulfide? a. Which structure had the shortest bond length between the central and each terminal atom?

b. Which structure has the greatest bond energy in it individual bonds?

c. Provide an explanation for your answer to parts a) and b) using principles of chemical bonding.

25. Draw the Lewis structures for sulfur trioxide and the sulfate ion (include resonance if applicable).

26. What is the effect number of bonds between the sulfur atom and each oxygen atom in sulfur trioxide?

CDO AP Chemistry Unit 6 Problem Set

27. What is the effective number of bonds between the sulfur atom and each oxygen atom in the sulfate ion?

28. In which compound, sulfur trioxide or the sulfate ion, is the bond length between each sulfur and oxygen atom the shortest? Explain.

29. In which compound, sulfur trioxide or the sulfate ion, is the bond energy between each sulfur and oxygen atom the greatest? Explain.

30. Draw the Lewis structures for the perchlorate ion and the chlorate ion (include resonance if applicable).

CDO AP Chemistry Unit 6 Problem Set

31. Is the bond length between the chlorine atom and the oxygen atoms in the perchlorate ion less than it is in the chlorate ion? Explain

32. Draw the Lewis structures for the carbon dioxide and the carbonate ion (include resonance if applicable).

33. What is the effective number of bonds between the carbon atom and each oxygen atom in carbon dioxide?

34. In which structure, carbonate or carbon dioxide, is the bond length between the carbon atom and each oxygen atom the shortest? Explain

CDO AP Chemistry Unit 6 Problem Set

35. In which structure carbonate or carbon dioxide, is the bond energy between the carbon atom and each oxygen atom the greatest? Explain.

36. Indicate the positive and negative poles for the following and rank the following in order of increasing polarity. O – C, O – N, O – O, and O – F.

37. Indicate the positive and negative poles for the following and indicate which bond from each set is most polar?

a. B – N or B – F

b. Si – O or Si – I

c. C – Cl or C – F