Midterm 3 Review Questions
Remember that this is not all inclusive. Please remember that everything from in class, homework and videos are
testable.
If given two resonance structures of equal stability. How does this affect bond order? How does this
affect the location of formal charges?
Sigma bonding electrons are shared only amongst the atoms in the specific bond. Pi bonds are
delocalized to be an average of resonance structures. The bond order is an average of all the lewis
structures The formal charge is an average of all the lewis structures.
For each formula, draw the lewis structure: O3. State the charge on each oxygen and the bond order.
Bond order: 3/2
Charge: -1/2
A) Draw the line structure of CH3CH(OH)CHCH2. What is the hybridization of the underline atoms.
O: sp3
C:sp3
What is the hybridization of the atoms below for each bond tell me which orbitals are used for bonding.
. (On the exam I would mark specific ones since obviously it would be too much to ask you to do all of
them. Here just do all of them).
Example answer for one of them.
The Nitrogen in the ring: sp3 hybridized (note don’t
forget about the lone pair that isn’t drawn in line
structures).
The bond to the hydrogen is a sigma bond formed
with the nitrogen’s sp3 orbital and Hydrogen’s s
orbital.
The bond to the carbons (they happen to be identical in this case). Are formed with nitrogen’s sp3
orbital and carbons sp2 orbital.
Use the Lewis structure below to answer the following questions.
The bond length for a single Cl-O bond is 170 pm, the bond length for a double Cl-O bond is 144pm.
What would you expect the bond length of the Cl-O bond in chlorite to be?
157pm
What is the formal charge on the oxygen of the chlorite atom?
-0.5
Would you expect to have the same experimental bond order on both ions?
no
Given the structures below, answer the following questions: (Note: no lone pairs are shown, you may fill
if necessary to answer the questions)
What is the bond order of the sulfate SO bond?
1.5
Which ion has the longest bonds?
phosphate
What is the charge on the oxygen of the phosphate?
-3/4
For the molecule below label each orbital.
Explain the process for determining molecular geometry? What role does hybridization play in this
process?
Bond angles are determined by spacing out bonded atoms and lone pairs as far apart in three
dimensional space as possible. Lone pairs get more room than bonds, deviating ideal bond angles
slightly.
Hybridization allows these angles to be possible given the possible orbitals for bonding.
What is the difference in bond angles for something that is t-shaped vs trigonal planar? What causes this
to be different considering that both geometries have a coordination number of three?
Trig planar molecular geometries (120 degree bond angles) has a steric number of three rather than tshaped (bond angle <90) steric number of 5. We must incorporate the two lone pairs into the structure
when determine the structure of the molecule.
For each formula, draw the lewis structure, give the hybridization and geometry of the bolded element
and state whether the molecule is polar. (Since this exam is mainly focused on the hybridization and
polarity that is most likely what would be asked, however being able to do
everything is good practice for the final and you are more likely to get the
polarity correct if you know the proper geometries).
A) PCl3
B) O3
C) BrF5
Hybridization __sp3
Geometry_____tetrahedral____
Is the molecule polar? ____yep
Hybridization _sp3d2_
Geometry_______square pyramidal
Is the molecule polar? _you betcha_
Hybridization ___sp2__
Geometry______bent_____
Is the molecule polar? ___yes_
Given the following reaction, calculate the maximum mass of copper (II) hydroxide that can be formed
when 2.00 g of sodium hydroxide is added to 80.0 mL of 0.500 M Cu(NO3)2 (bookwork).
Cu(NO3)2 +2NaOH  2Na(NO3)+ Cu(OH)2
2.44g
How many moles of calcium carbonate are produced when 2 moles of calcium cyanide react with 7
moles of water, according to the following balanced equation:
Ca(CN)2 + 3 H2O  CaCO3 + 2NH3
2
How many moles of excess reagent are left over when 2 moles calcium cyanide reacts with 7 moles of
water, according to the following balanced equation:
Ca(CN)2 + 3 H2O  CaCO3 + 2NH3
1
If the reaction yield is only 50%. How many moles of methane must be combusted to produce 2 moles of
CO2?(Hint: mole ratio of methane to CO2 is 1:1)
4
If the solution in the previous question is reacted with 400. mL 0.105 M CaCl2, how many grams of the
insoluble sulfate salt is formed? 4.28g
Use this reaction to answer the following questions:
How many moles of carbon dioxide are produced when 4 moles of methane react with 7 moles of
oxygen?
3.5 mol
How many moles of excess reagent is left over when 4 moles of methane react with 7 moles of oxygen?
0.5 moles
For a particular chemical reaction the theoretical yield was 12 grams of product, but the actual yield was
3.0 grams. What is the percent yield of this reaction?
25%