CHEMISTRY 1201, Lecture section 02 and 03
SAMPLE EXAM 3 - SPRING 2002 - format modified Apr.26
answers


Consider the best Lewis diagrams for the molecules given in the list below when answering the next 8 questions  

(a) N 2F2    (F~N~N~F)

(b) PF 3

(c) O 3   (O~O~O)

(d) XeF 4

(e) NO

(f) BeCl 2

(g) SF 4

Question 1

Which molecule is neutral yet has atoms that have a formal charge?                        .


Question 2

Which molecule is a radical?                        .


Question 3

Which in the gaseous phase disobeys the octet rule by being electron defficient but in the solid state can obey the octet rule by forming long chains?                        .


Question 4

Which molecule disobeys the octet rule by expanding the octet of its central atom by 2 electrons?                        .


Question 5

Which molecule displays a sp3 d2 hybridized electronic geometry and a square planar molecular geometry?                        .


Question 6

Which molecule has bond angles that are less than the idealized 109.5 o for an sp3 hybridized species?                        .


Question 7

Which atom can have two structurally similar yet different arrangements of atoms, one which displays molecular polarity and one which does not?                        .


Question 8

Which molecule has a see-saw molecular shape?                        .


Question 9

Which of the structures shown below are not valid Lewis diagrams for CO 2 ?

a)
b)
c)
d)
e)   all of the above

Question 10

Using the bond energy data below what is the estimated heat of reaction when two moles of ethene react with two moles of chlorine gas as shown in the following equation?

H 2C=CH2 + Cl2 --> ClH2C-CH2Cl       (each C atom is bonded to two H atoms and one Cl atom, and then attached to the other C atom)

D C-H = 413 kJ/mol

D C-C = 347 kJ/mol

D C=C = 614 kJ/mol

D C-Cl = 339 kJ/mol

D Cl-Cl  = 239 kJ/mol

  a) -172 kJ
  b) -344 kJ
  c) 172 kJ
  d) 344 kJ
  e) 167 kJ

Question 11

Using the bond energy data below, is the reaction of one mole of ethene with one mole of water to produce ethanol exothermic?

H 2C=CH2 + H2O -->  CH3CH2OH

D C-H = 413 kJ/mol

D C-C = 347 kJ/mol

D C=C = 614 kJ/mol

D C-O = 358 kJ/mol

D O-H = 463 kJ/mol

  a) Yes
  b) No


Question 12

The formal charge of an atom is a measure of how the valence electron configuration of an atom has been changed once it is in a molecule.

a)   true
b)   false

Question 13

Which is the best representation of the hybrid orbitals for the carbon in formaldehyde, H2CO, (C serves as a hub for two single bonds to the hydrogen atoms, and once double bond to oxygen) ?

a)


b)


c)


d)


e)




Question 14

What is the respective order of hybridization of chlorine in ClO 2 -, ClO3- and ClO 4 - ?

a)   sp, sp2, sp3
b)   sp2, sp 3, sp3
c)   sp3, sp 3, sp3
d)   sp3, sp 3d, sp3d 2
e)   sp3d 2 , sp3d 2 , sp3d2


Question 15

Identify which of the statements regarding Valence Bond Theory or Hybridization is false when applied to a molecule such as water.

a)   Bonds between oxygen and hydrogen atoms form as the result of orbital overlap.
b)   Hydrogen atoms need to undergo hybridization
c)   Oxygen utilizes sp 3 hybrid orbitals to form bonds with hydrogen and to house lone pairs of electrons.
d)   Orbitals are hybridized in order to form a degenerate orbital set from a number of non-degenerate atomic orbitals.
e)   The number of hybrid orbitals equals the number of atomic orbitals that enter the hybridization.

Question 16

Which of the following equations shows an incorrect relationship between pressures given in terms of different units?

a) 1.20 atm = 122 kPa
b) 152 mmHg = 203000 Pa
c) 0.760 atm = 578 mmHg
d) 1.00 torr = 2.00 mmHg
e) 1.00 atm = 760 torr

Question 17

Methane, CH4, is sold in 43.8 L cylinders, each containing 5.54 kg of CH4. What is the pressure inside the cylinder at 20oC?

a) 12.9 atm
b) 28.2 atm
c) 190 atm
d) 3040 atm
e) 13000 atm

Question 18

Nitroglycerin, C3H5N3O9 , decomposes by the reaction below. How many L of carbon dioxide will be produced from the explosion of 0.600 g of nitroglycerin ar 425 oC and 152000 Pa?

4 C3H5N3O9 (l) --> 12 CO 2(g) + 10 H2O(g) + 6 N 2 (g) + O2(g)


a) 0.0101 L
b) 0.0615 L
c) 0.148 L
d) 0.303 L
e) 0.737 L


Question 19

What is the average speed (rms) of N2 on a very cold day (-25 oC)?

a) 126 m/s
b) 221 m/s
c) 470 m/s
d) 515 m/s
e) 12800 m/s