CHEMISTRY 150
November 8th, 2012
Brian J. MacLean
NAME:_______________________________
__________________________________________________________________________________________
INSTRUCTIONS
This quiz should contain a total of ten pages. A periodic table, equations, and other relationships are given on
the last page. Read section instructions carefully. Show all work when solving calculation-style problems.
Question
Marked out of
A 1-15
30
B1
18
B2
18
B3
14
B4
20
Total
100
Obtained
Part A: Multiple choice. Circle the correct answer (a, b, c, or d) to answer the question posed in each case.
There is only one correct answer in each case.
A1) Which of these molecules is linear?
a) SO2
b) HOF (O atom central)
c) HCN
d) H2S
Chapter 5, slide 17. HCN is the only Lewis structure for which the central atom is surrounded by 2
electron groups.
A2) The formula for hydrogen sulfide would be?
a) H2SO4
b) H2S
c) HS
d) S2Chapter 5, slide 34, naming molecular compounds.
A3) How many total valence electrons are present in CF4?
a) 8
b) 18
c) 28
d) 32
Chapter 5, slide 11, step 1.
A4) What is the mass of sulphur that is present in 3S4N4 molecules?
a) 6.4 x 10-22 g S
b) 12 amu
c) 32.07 g S
d) 384.84 g S
Chapter 6 slides. Hint: you are looking for the mass of sulphur that is present in 3 molecules of
something - this would be a pretty small mass.
A5) For the following chemical reaction, the coefficient for O2 in the balanced equation would be:
CH3OH + O2  CO2 + H2O
a)
1
b)
2
c)
3
d)
4
Chapter 6, slide 24
2CH3OH + 3O2  2CO2 + 4H2O
A6) A heated solution is allowed to cool to room temperature. Cooling the solution in this way results in
the formation of a solid. Before cooling, the solution
a)
was supersaturated
b)
was saturated
c)
was unsaturated
d)
had more solute
See chapter 8, slide 7. The supersaturated solution would be created at a high temperature, and then
allowed to cool.
A7) Beer (which is 5% (v/v) ethanol/water) is considered to be:
a)
a pure liquid
b)
a heterogeneous mixture
c)
a non-aqueous solution
d)
an aqueous solution
Chapter 8, slide 9: 5% (v/v) ethanol/water solution has 5mL of ethanol in 100 mL of solution. H2O
is the solvent (aqueous solution)
A8) The amount of CO2 that is obtained (in practice) from the chemical reaction shown in question A5 is
called the
a)
percent yield
b)
actual yield
c)
theoretical yield
d)
reactant
Chapter 6, slide 36
A9) Chemical bonds for which the difference in electronegativity is greater than 2.0 are called
a)
ionic
b)
non-polar covalent
c)
polar covalent
d)
intermolecular
Chapter 5, slide 29
A10) The strongest type of attractive forces that exist between the molecules present in a sample of pure
CH4 are
a)
hydrogen bonds
b)
dipole-dipole forces
c)
London forces
d)
covalent bonds
CH4 is non-polar, so no dipole-dipole forces are possible. Also, no N-H, O-H, or F-H bonds, so no
H-bonding. A covalent bond is an intramolecular force. London forces are always present.
A11) The process which results in the transformation of matter in the liquid to the gas state is called
a)
sublimation
b)
condensation
c)
deposition
d)
evaporation
Chapter 7, slide 26
A12) The law that relates the pressure and volume of a gas (when temperature and amount of gas are held
constant) is called
a)
Henry’s law
b)
Dalton’s law
c)
Charles’ law
d)
Boyle’s law
Chapter 7, slide 14. Sorry, no Murphy’s Law.
A13) Which of these properties are characteristic of gases?
a)
high compressibility
b)
high density
c)
small thermal expansion
d)
definite volume and indefinite shape
Chapter 7, slide 9. Gases have high compressibility, low density, moderate thermal expansion, and
no definite volume or shape.
A14) Which of the following should have the highest boiling point?
a) Br2
b) Cl2
c) I2
d) F2
Chapter 7, slide 41. All are non-polar molecules, and London forces dictate the boiling points, and
London forces increase with increasing molar mass.
A15) Liquids that possess low boiling points are
a) flammable
b) volatile
c) non-volatile
d) polar
Chapter 7, slide 30
Part B: Problems. Answer each of the following problems. Where appropriate, answer with the proper number
of significant figures and correct units.
B1)
Draw Lewis structures for each of the following chemical formulas. In each case, indicate the
molecule’s (or ion’s) molecular geometry, and whether it is polar or non-polar [18 points/6 each] (Chapter 5,
slides 11-21)
a) ClO2Molecular geometry angular/bent
Polar ? Yes /No
b) ClO2+
Molecular geometry angular/bent
Polar ? Yes /No
c) PH3
Molecular geometry trigonal pyramid
Polar ? Yes /No
Note: a number (>10) of people indicated a molecular geometry of “linear (bent)” for the first two structures.
“Linear” and “bent” do not mean the same thing. This is kind of like answering a question with “yes (no)”.
B2a) How many grams of water are present in 325g of a 6.00% (m/m) solution of LiCl? [8 points] (Chapter 8,
slides 18-21)
 mass _ of _ LiCl 
 x100%
%m / m   
 mass _ of _ solution 
 mass _ of _ LiCl 
 x100%
6.00%  
 325 g _ solution 
 mass _ of _ LiCl 

0.0600  
 325 g _ solution 
mass _ of _ LiCl  19.5 g
Since the solution mass is 325g, the mass of water in 325g of the 6.00% (m/m) solution would be:
325g – 19.5g = 305.5g
(or 306g to 2 significant digits)
b) How many moles of LiCl are present in this solution? [6 points] (Chapter 6, slide 9)
19.5g _ LiCl 
1mol _ LiCl 
  0.460014154mol _ LiCl  0.460mol _ LiCl
 42.39 g _ LiCl 
c) How many Li+ ions are present in this amount of LiCl? [4 points] (Chapter 6, slides 12-15)
There are Avogadro’s # of objects in 1 mol of anything. For 0.460 mol LiCl, there should be 0.460 mol
of Li+ ions:
 1mol _ Li  
  0.460mol _ Li 
0.460moles _ LiCl 
 1mol _ LiCl _ 
Using Avogadro’s #, the number of Li+ ions present could be calculated as:
10 Li _ ions 
  2.7692852 x10
0.460moles _ Li  6.021xmol
_ Li
23




…or 2.77x1023 Li+ ions to 3 significant digits.

23
_ Li  _ ions
B3a) Which of the following compounds would you expect to be soluble in water? Indicate with “soluble”
where appropriate. [8 points] (Chapter 8, slide 15 – did these examples in class)
i.
SO2
Molecule is polar. So is water, so SO2 should be water –soluble.
ii.
Na3PO4
For this ionic compound’s water solubility, see the attached solubility table (soluble).
iii.
BaCO3
As for “b”, see solubility table (insoluble)
iv.
CH4
CH4 is a non-polar molecular compound. It should insoluble in water.
b) List three factors that increase the rate of solution formation [6 points] (Chapter 8, slide 12)
i)
Temperature
ii)
Agitation/stirring
iii)
Surface area of solute/state of subdivision
B4)
When water contacts sodium, the following reaction occurs (note: the equation is not balanced):
2H2O(l) + 2Na(s)  2NaOH(aq) + H2(g)
a)
How many grams of H2 are produced when 11.0g of sodium are reacted with water (assume there is
more than enough water to react all of the sodium) [8 points] (Chapter 6, slides 32-35)
 1mol _ Na  1mol _ H 2  2.02 g _ H 2 
  0.483253588 g _ H 2  0.483gH 2


11.0 g _ Na
 22.99 g _ Na  2mol _ Na  1mol _ H 2 
b) If this hydrogen is produced in a 10.0 L container at 25oC, what will the pressure of the gas be? [6
points] (Chapter 7, slide 21)
From above, if we stopped the calculation before the last step, we would have the number of moles of H2 in the
container:
 1mol _ Na  1mol _ H 2 

  0.239234449mol _ H 2  0.239mol _ H 2
11.0 g _ Na
 22.99 g _ Na  2mol _ Na 
PV  nRT
nRT
P
V
P

0.239234...mol  0.0821 L.atm
298 K 
.

5.0 L 
mol K 
P  1.17061244atm  1.2atm
c) If the volume of the H2 gas is tripled while the pressure is held constant, what will the temperature (oC)
of the gas be? [6 points] (Chapter 7, slide 17 or 19)
V1 V2
TV

 T2  1 2
T1 T2
V1
T2 
298K1 15.0 L 
5.0 L 
T2  894 K
Converting to oC, 894-273 = 621oC (or 620oC to 2 significant digits)
Equations and other relationships
(some may be useful, some…maybe not)

PV  nRT
L. atm
R  0.0821
mol . K
1atm  760torr  760mmHg
V1 V 2

T 1 T2
P1V1  P2V 2
P1V1 P2V 2

T1
T2
PTot  PA  PB  PC ...
T ( K )  T ( o C )  273

given _ units  desired _ units   desired _ units
 given _ units 
 mass _ of _ solute 
 * 100%
%( m / m)  
 mass _ of _ solution 
 volume _ of _ solute 
 * 100%
%(v / v)  
 volume _ of _ solution 