WebAssign
Allison Perea
C HEM 1212, section 92-111, Spring 2014
Instructor: Martina Sumner
Due : Monday, February 24 2014 08:00 PM EST
2014-02 CHEM 1212 Exam 1 (Exam)
Current Score : 50.57 / 100
The due date for this assignment is past. Your work can be viewed below, but no changes can be made.
1. 0/5 points | Previous Answers
Decane has a vapor pressure of 7.96 torr at 40°C. What is the normal boiling point of decane? The
ΔHvap of decane is 39.58 kJ/mol.
P2
1
−ΔHvap 1
=
−
T
T
P1
R
2
1
446.9737
174 °C
ln
2. 5/5 points | Previous Answers
Place these metal cations in order of increasing heat of hydration. Be sure to separate the ions with
less than symbols (<).
Cs+; Ba2+; Fr+
Fr+ < Cs+ < Ba2+
Fr+ < Cs+ < Ba2+
Fr^+ < Cs^+ < Ba^2+
3. 3/5 points | Previous Answers
Identify all possible types of intermolecular forces that can form between particles of each
substance below. (Select all that apply.)
(a)
CS2
dipole-dipole interactions
hydrogen bonding interactions
ion-dipole interactions
London dispersion forces
(b)
CHCl3
dipole-dipole interactions
hydrogen bonding interactions
ion-dipole interactions
London dispersion forces
(c)
Ar
dipole-dipole interactions
hydrogen bonding interactions
ion-dipole interactions
London dispersion forces
(d)
NH3
dipole-dipole interactions
hydrogen bonding interactions
ion-dipole interactions
London dispersion forces
(e)
H2Te
dipole-dipole interactions
hydrogen bonding interactions
ion-dipole interactions
London dispersion forces
Tutorial
Identify all possible types of intermolecular forces that can form between particles of each
substance below.
(a)
BeH2
(b)
CHBr3
(c)
Ar
(d)
H2O
(e)
H2Se
Step 1 of 3
Name and describe each type of attractive intermolecular force.
There are four types of intermolecular forces of attraction.
•
(No Response)
Ion-dipole interactions occur between an ion, which has either a positive
or a negative charge, and a dipolar molecule that carries a partial positive charge on one end
and a partial negative charge on the other. These types of interactions are especially important
when determining how a solute and a solvent will interact in forming a solution. These
interactions are rare in pure substances.
•
(No Response)
Dipole-dipole interactions occur between polar molecules that carry partial
positive and partial negative charges on opposite ends of their structures. The partial charges
are attracted to the respective oppositely-charged end of other dipoles.
•
(No Response)
Hydrogen bonding interactions can occur if a molecule contains a small,
highly electronegative atom, such as F, O, or N, that is bonded to a hydrogen atom. In these
cases, the hydrogen atom is much less electronegative than the atom it is bonded to. The
difference in electronegativity results in an unequal distribution of bonding electrons, creating a
partial positive charge on the hydrogen and a partial negative charge on the electronegative
atom. The partially-positive hydrogen is then attracted to the partially-negative charges on
another molecule, while the partially-negative atom can bond with partially-positive hydrogen
atoms on another molecule.
•
(No Response)
London dispersion forces are weak attractions that result from the
temporary distortion of electron densities in two nearby atoms. These forces exist in all
substances, although they vary in strength in different substances. The distortions cause
electrons to temporarily group on one side of an atom (asymmetrically), creating a temporary
dipole. When this occurs in both nearby atoms, the atoms will temporarily exert an attractive
force on each other. Molecules can also be attracted to one another by these forces.
Describe dipole- dipole interactions .
Describe ion- dipole interactions .
Describe hydrogen bonding.
Solution or Explanation
Step 1 of 3
Name and describe each type of attractive intermolecular force. There are four types of
intermolecular forces of attraction.
•
Ion-dipole interactions occur between an ion, which has either a positive or a negative
charge, and a dipolar molecule that carries a partial positive charge on one end and a
partial negative charge on the other. These types of interactions are especially important
when determining how a solute and a solvent will interact in forming a solution. These
interactions are rare in pure substances.
•
Dipole-dipole interactions occur between polar molecules that carry partial positive and
partial negative charges on opposite ends of their structures. The partial charges are
attracted to the respective oppositely-charged end of other dipoles.
•
Hydrogen bonding interactions can occur if a molecule contains a small, highly
electronegative atom, such as F, O, or N, that is bonded to a hydrogen atom. In these
cases, the hydrogen atom is much less electronegative than the atom it is bonded to.
The difference in electronegativity results in an unequal distribution of bonding electrons,
creating a partial positive charge on the hydrogen and a partial negative charge on the
electronegative atom. The partially-positive hydrogen is then attracted to the partiallynegative charges on another molecule, while the partially-negative atom can bond with
partially-positive hydrogen atoms on another molecule.
•
London dispersion forces are weak attractions that result from the temporary distortion of
electron densities in two nearby atoms. These forces exist in all substances, although
they vary in strength in different substances. The distortions cause electrons to
temporarily group on one side of an atom (asymmetrically), creating a temporary dipole.
When this occurs in both nearby atoms, the atoms will temporarily exert an attractive
force on each other. Molecules can also be attracted to one another by these forces.
Step 2 of 3
Identify and describe the types of intermolecular forces that can exist between the given
atoms or molecules. (a)
CS2
This molecule is nonpolar. The linear shape of CS2 results in a molecule with a net
dipole moment of zero even though it has polar bonds. CS2 also cannot participate in
hydrogen bonding interactions because it has no hydrogen atoms in its structure.
Therefore, the only intermolecular forces that could exist between CS2 molecules are
London dispersion forces.
(b)
CHCl3
This molecule is polar. The sum of the dipole moments of the individual bonds in this
tetrahedral molecule gives rise to a net dipole moment of greater than zero. Molecules
of CHCl3 can interact via dipole-dipole interactions and London dispersion forces. It
does not form hydrogen bonds because the carbon in its H–C bonds is not sufficiently
electronegative to create hydrogen bonding interactions.
(c)
Ar
This atom is nonpolar because it is a single atom and has no bonds to other atoms.
Therefore, the only intermolecular forces that could exist between Ar atoms are
London dispersion forces.
(d)
NH3
This molecule is polar. The H–N bond is polar and creates a net dipole moment of
greater than zero for the molecule. Molecules of NH3 can interact via hydrogen
bonding interactions because of the high electronegativity of nitrogen. They can also
participate in dipole-dipole interactions and London dispersion forces.
(e)
H2Te
This molecule is polar. The sum of the dipole moments of the individual bonds in this
molecule gives rise to a net dipole moment of greater than zero. It does not form
hydrogen bonds because the tellurium in its H–Te bonds is not sufficiently
electronegative to create hydrogen bonding interactions. However, molecules of H2Te
can interact via dipole-dipole interactions and London dispersion forces.
Step 3 of 3
[Summarize]
Identify all possible types of intermolecular forces that can form between particles of each
substance below. (Select all that apply.)
(a)
CS2
London dispersion forces
(b)
CHCl3
dipole-dipole interactions
London dispersion forces
(c)
Ar
London dispersion forces
(d)
NH3
dipole-dipole interactions
hydrogen bonding interactions
London dispersion forces
(e)
H2Te
dipole-dipole interactions
London dispersion forces
Did you recall the types of intermolecular interactions that can exist between atoms or molecules?
Did you recall that a molecule's shape is important in determining if it is polar? Did you recall the
criteria for hydrogen bonding interactions to occur?
Supporting Materials
Periodic Table
Constants and Factors
Supplemental Data
4. 0/5 points | Previous Answers
The atomic orbitals of metals atoms overlap in the solid to form molecular orbitals that explain why
metals are such good conductors of electricity. If we consider only the valence shell s and p
orbitals of magnesium, how many molecular orbitals would be formed from 5,000 magnesium atoms?
5000
20000 molecular orbitals
Again considering only the valence electrons from 5,000 magnesium atoms, how many of these
molecular orbitals would be filled?
1666.666
5000 molecular orbitals would be filled
5. 5/5 points | Previous Answers
Place the following compounds in order of increasing vapor pressure.
pentane
Lowest Vapor Pressue
propane
propanone
1-butanol
1-butanol
propanone
Highest Vapor Pressure
propanone
pentane
pentane
propane
propane
1-butanol
6. 0/5 points | Previous Answers
A hydrocarbon has the empirical formula CH2. When 1.631 grams of the hydrocarbon are dissolved in
30 grams of benzene, the boiling point of the solution is 81.50°C. What is the molecular formula for
the hydrocarbon?
21CH2
C7H14
21CH_2
Freezing Point
Kfp
Boiling Point
Kbp
5.53°C
-5.12°C/m
80.10°C
2.53°C/m
benzene
7. 5/5 points | Previous Answers
The lattice energy of potassium bromide is the energy required for the following reaction.
KBr(s) → K+(g) + Br−(g)
ΔHrxn = ΔHlattice = 690 kJ/mol
Use this information and the data table to determine the ΔHf of potassium bromide:
K(s) + 1/2 Br2(g) → KBr(s) ΔHf = -394
Br2(g) → 2 Br(g)
K(s) → K(g)
Br(g) + e− → Br−(g)
K(g) → K+(g) + e−
ΔHrxn
ΔHrxn
ΔHrxn
ΔHrxn
-393.5 kJ/mol
= 224 kJ/mol
= 89 kJ/mol
= −324 kJ/mol
= 419 kJ/mol
8. 5/5 points | Previous Answers
Testtakium ( 203 Tk ; 203.52 g/mole) was recently discovered by researches in the Department of
127
Chemistry at UGA. It is a metal with a density of 11.6617 g/cm3. The X-Ray crystallography lab was
able to determine that testtakium exists in a cubic lattice with an edge length of 387.0 pm. The
testtakium crystal lattice is probably
primitive cubic
face-centered cubic
body-centered cubic
9. 3.32/5 points | Previous Answers
The heat of solution (ΔHsol) for potassium perchlorate in water is +51.04 kJ/mol. We know that the
attractive forces between the solute particles must be greater than
greater than the
attractive forces between the solute and the solvent particles.
The heat of solution (ΔHsol) for ammonium acetate in water is -2.38 kJ/mol. We know that the
attractive forces between the solute particles must be less than
less than the
attractive forces between the solute and the solvent particles.
The heat of solution (ΔHsol) for gases is always exothermic because:
there are no intermolecular forces between molecules in the gas phase.
the concentration of the gas is dependent on the partial pressure of the gas over the
solvent.
the gas molecules undergo a chemical reaction with water.
the attraction between solute and solvent particles is enormous.
10.0/5 points | Previous Answers
A solution is made by adding 30.0 mL of ethanol to 30.0 mL of water. What is the total vapor
pressure over the solution at 20°C?
30.55
Compound
ethanol
water
23.7 torr
Formula
Density
VP of Pure
Substance @ 20°C
CH3CH2OH
0.789 g/mL
43.6 torr
H2O
0.998 g/mL
17.5 torr
11.0/5 points | Previous Answers
Rank these aqueous solutions from lowest freezing point to highest freezing point.
0.40 m KNO3
0.20 m C2H6O2
0.15 m Na3PO4
0.40 m C6H12O6
Lowest Freezing Point
0.20 m C2H6O2
0.40 m C6H12O6
0.15 m Na3PO4
Highest Freezing Point
0.40 m KNO3
0.40 m KNO3
0.15 m Na3PO4
0.40 m C6H12O6
0.20 m C2H6O2
12.5/5 points | Previous Answers
The rate equation for the reaction where A and B react to form products was determined to be
rate = k[A]1[B]2 . If the concentration of A is halved and the concentration of B is doubled, what
happens to the rate of reaction?
The rate increases by a factor of 8.
The rate increases by a factor of 4.
The rate increases by a factor of 2.
The rate is unchanged.
The rate decreases by a factor of 2.
The rate decreases by a factor of 4.
The rate decreases by a factor of 8.
13.5/5 points | Previous Answers
An experiment in CHEM 1212 requires students to prepare a 0.125 M aqueous solution of silver(I)
nitrate.
Michael fills a 250.0 mL volumetric flask to the calibration line with water. Michael then weighs out
5.31 grams of silver(I) nitrate and adds it to the volumetric flask.
Sarah weighs out 5.31 grams of silver(I) nitrate and adds it to a 250.0 mL volumetric flask. Sarah
then fills the volumetric flask to the calibration line with water.
Which student has correctly prepared a 0.125 M aqueous solution of silver(I) nitrate?
Michael
Sarah
14.5/5 points | Previous Answers
Given the hypothetical reaction where A and B react to form C and D, if the rate of consumption of
A is 0.073 M/min what is the rate of consumption of B and rates of appearance of C and D?
3 A +2 B→ 4 C +2 D
Rate of consumption of B = .04866
Rate of appearance of C = .09733
Rate of appearance of D = .048666
0.049 M/min
0.097 M/min
0.049 M/min
15.3/5 points | Previous Answers
The apparatus shown is filled with two (2) aqueous solutions. The
solutions are separated by a semipermeable membrane (osmotic
membrane). For each set of solutions decide on which side, if either,
the fluid level will rise.
Solution A
Solution B
Fluid levels will remain the same.
0.90 M methanol 0.90 M glucose
Fluid levels will remain the same.
Fluid level on side B will rise.
0.40 M ethylene
0.50 M
glycol
ethylene glycol
0.60 M
potassium
sulfate
Fluid levels will remain the same.
0.60 M
ethylene glycol
1.0% w/w
5.0% w/w
glucose
glucose
5.0% w/w
5.0% w/w
glucose
sucrose
Solute
Fluid level on side B will rise.
Fluid level on side A will rise.
Fluid level on side B will rise.
Fluid level on side B will rise.
Fluid levels will remain the same.
Fluid level on side A will rise.
Formula
Molar Mass
ethylene glycol
C2H6O2
62.07 g/mol
glucose
C6H12O6
180.16 g/mol
methanol
CH3OH
32.04 g/mol
potassium sulfate
K2SO4
174.27 g/mol
sodium bromide
NaBr
102.89 g/mol
sodium chloride
NaCl
58.44 g/mol
sucrose
C12H22O11
342.30 g/mol
16.0/5 points | Previous Answers
An aqueous solution of sulfuric acid, H2SO4, has a concentration of 0.150 m and a density of
1.1015 g/mL. What is the concentration of sulfuric acid expressed as molarity?
11.2329
0.163 M
17.2.5/5 points | Previous Answers
Which molecule(s) exhibits hydrogen bonding as the pure substance?
Which molecule(s) could exhibit hydrogen bonding with ammonia, NH3.
18.0/5 points | Previous Answers
Use the data presented in the table to determine the rate equation for the hypothetical reaction
shown.
A + 2 B + C → products
Initial Rate
Experiment
[A] (M)
[B] (M)
[C] (M)
1
0.0005
0.0005
0.0005
9.76 ✕ 10−11
2
0.0005
0.0005
0.0010
1.95 ✕ 10−10
3
0.0005
0.0010
0.0010
7.81 ✕ 10−10
4
0.0010
0.0020
0.0020
6.25 ✕ 10−9
(M/min)
When entering the rate of reaction it should be entered in the form rate=k[A]x [B]y [C]z. Exponents
of one (1) may be omitted. Reaction components raised to the zeroth power may also be omitted.
k[A]2[C]
rate = k[A]0[B]2[C]1 or rate = k[A]0[B]2[C] or rate = k[B]2[C]1 or rate = k[B]2[C]
k[A]^2[C]
19.0/5 points | Previous Answers
In Anchorage, AK the average low temperature is -9.00°C. How much ethylene glycol, C2H6O2, must
be dissolved in 1.00 kg of water to make a radiator fluid that wouldn't freeze until the temperature
reached -15.00°C?
8.064516
501 g ethylene glycol
Freezing Point
Kfp
Boiling Point
Kbp
0.00°C
-1.86°C/m
100°C
0.5121°C/m
water
20.3.75/5 points | Previous Answers
Identify the triple point
in the phase diagram.
P= 5.19
5.19
atm
T= -60
-56.6
°C
Identify the critical point
in the phase diagram.
P= 73
73
atm
T= 31
°C
31