Chapter 9 practice exam

1. Draw the most accurate lewis structure for SeO2 if necessary include a resonance structure.

2. in which compound below is it inappropriate to use a line or dash to represent a shared electron pair in a bond

a. KCl b. HClc. Br2

d. BrFe. I2

3. Which compound is likely to have an incomplete octeta. NH3 b. SO3

c. N2Od. BH3

e. None of the above

4. Which of the following molecules or ions are likely to be free radicalsa. N2O and OCl-

b. N2O and NOc. NO and OCl-

d. NO and ClO2

e. OCl- and ClO2

5. Which of the following are true when making a lewis structurea. The most electronegative element is placed in the centerb. No matter what all elements must have an octet c. A single line represents a shared electrond. Ions with a positive charge add electrons to the compound and ions

with a negative charge subtract electrons from the compounde. The atom that requires the largest number of electrons is placed in

the center

6. Place the following elements in order of decreasing electronegativity S Cl Se

a. Cl > S > Se b. Se> S >Clc. Cl > Se > Sd. Se > Cl > Se. S > Cl > Se

7. Which of the following is false regarding electronegativitya. A non-polar bond is formed between an electronegativity difference of

0.4b. An ionic bond forms when the electronegativity difference is 2.1c. F is the most electronegative elementd. A polar molecule can have nonpolar bonds.e. Electronegativity is the tendency of an atom to attract electrons to

itself when bonded to another atom

8. Why is it not recommended to draw double bonds between the Be atom and the Cl atoms in BeCl2

a. It would give positive formal charges to the chlorine atoms and a negative formal charge to the beryllium atom

b. There would be too many valence shell electrons c. It would result in more than eight electrons around berylliumd. It would result in more than eight electrons around each chlorine

atom e. It would result in the formal charges not adding up to zero

9. Which of the following is false regarding formal charge?a. The best lewis structure has a formal charge of zero on all atomsb. A negative FC will go on the least electronegative atomc. FC = valence electrons- lone pair electrons- # of bondsd. The best lewis structure has the lowest formal charge on each atome. The overall formal charge is represented by the charge of the

molecule

10. Given the electronegativities below, which single bond has the lowest degree of polarity

i. Element: H C N O ii. Electronegativity 2.1 2.5 3.0 3.5

a. C-Hb. N-Hc. O-Hd. O-Ce. O-N

11. predict the formula for magnesium phosphide? What is the total number of electrons transferred

a. Mg2P3 ; 3 electrons are transferred from Mg to Pb. Mg3P2 ; 6 electrons are transferred from Mg to P c. Mn3P ; 3 electrons are transferred from P to Mn d. MgP3 ; 6 electrons are transferred from Mg to P e. MgP2 ; 4 electrons are transferred from P to Mg

12. Which of the following is a possible valid Lewis structure for the compound which has the molecular formula

a. 1 and 2 b. 2c. 3d. 2 and 3e. 1,2 and 3

13. Draw the correct dipole moment for CO2 and H2S

14. which of the following species will have a Lewis structure most like that of the hydronium ion , H3O+

a. NO3-

b. NH3

c. SO3

d. CO32-

e. H2CO

15. Consider the reaction : CH4 + Cl2 CH3Cl + HClCalculate the overall enthalpy change for the reaction (Hrxn) using the bond energy data given

C-H 414 kJ O=O 498 kJ H-Cl 431 kJ C-O 360 kJC-Cl 339 kJ C=O 799 kJCl-Cl 243 kJ H-O 464 kJ

a. -92 kJb. + 92 kJc. -113 kJ d. 273 kJ e. 301 kJ

16. Given the data above calculate the enthalpy change for the combustion reaction (Hrxn) of CH4

17. the type of compound that is most likely to contain a covalent bond is which of the following

a. one that is composed of a metal from the far left of the periodic table and a nonmetal from the far right of the periodic table

b. a solid metalc. a substance held together by the electrostatic forces between

oppositely charged ions d. one that is composed of two nonmetals e. there is no general rule to predict covalency in bonds

18. Select the compound with the shortest and strongest carbon-carbon bond respectively

a. H2C=CH2

b. C2H6

c. H-C≅C-CH3

d. H2C=C=CH2

e. H3C-CH2-CH3

19. What is the formal charge on the nitrogen in the nitrate ion NO3-

a. -1b. 0c. +1d. +2

20. which of the following compounds is expected to have the strongest ionic bond

a. MgOb. KBrc. NaId. SrOe. CaS

21. In the resonance hybrid or experimentally determined structure of the nitrate ion (NO3

-) it is observed that a. All the bonds are single bonds b. All the bonds are double bonds c. All the bonds have a bond order of 1.33d. One bond is a double bond and the others are single bonds e. There are 23 valence electrons

22. In the Lewis structures of N2H2 a. There is a nitrogen-nitrogen triple bond b. There is a nitrogen- nitrogen single bond c. Each nitrogen has two nonbonding electron pairs (lone-pairs)d. Each nitrogen has one nonbonding electron pair (lone-pair)e. Each hydrogen has one nonbonding electron pair (lone pair)

23. The diagram below is the Born-Haber cycle for the formation of crystalline potassium fluoride KF

Which energy change (by number) corresponds to the lattice energy of KFa. 5b. 2c. 4d. 1e. 6

24. what is the total number of valence electrons in the Lewis structure of CH2ClCH2Cl

a. 14b. 12c. 18d. 10e. 26

25. which of the following best represents the Lewis structure for ozone O3

a. 1b. 2c. 5d. 4e. 3

26. Use formal charge to choose the best lewis structure for CH3SOCH3

27. which of the following is truea. to convert from one resonance structure to another, only electrons

can be movedb. to convert from one resonance structure to another, only atoms can

be movedc. to convert from one resonance structure to another, electrons and

atoms can both be moved d. to convert from one resonance structure to another, neither electrons

nor atoms can be movede. to convert from one resonance structure to another, electrons must

always be added

28. which molecule below has the largest dipole moment a. HBrb. HIc. HFd. HCle. H2