AP Chem
Semester 1 Review
1. When the following equation is balanced with whole number coefficients the sum of the coefficients is
CH
3
NH
2
+ O
2
= CO
2
+ H
2
O + N
2
A. 29
B. 14
C. 15
D. 37
E. 57
2. CH
4
+ O
2
= CO
2
+ H
2
O
How many grams of methane are required to react with 32 grams of oxygen?
A. 16
B. 32
C. 64
D. 128
E. 8
3. Which of these lists has the elements ranked correctly from greatest to smallest electronegativity value?
A. F, O, Cl, Br, C
B. F, O, Cl, C, Br
C. Br, C, Cl, O, F
D. C, Br, Cl, O, F
E. C, Br, O, Cl, F
4. Which of these has the species ranked correctly from greatest to smallest atomic radius?

A. F, O, Cl, Br, C
B. F, O, Cl, C, Br
C. Br, Cl, C, O, F
D. C, Br, Cl, O, F
E. C, Br, O, Cl, F
5. The values below are for the element unobtanium. How many valence electrons does unobtanium have?
IE1 IE2 IE3 IE4 IE5 IE6
1 unit 8 units 10 12 15 20
A. 1
B. 2
C. 3
D. 4
E. 5
6. A gas sample is held in a 3L container at 300K and the pressure is measured as 3 atm. What is the pressure when the temperature is lowered to 100K and the volume is decreased to 1L?
A. 1 atm
B. 3 atm
C. 9 atm.
D. 27 atm
E. .11 atm
7. A gas sample with 3 moles of gas has a volume of 4L. the gas sample is made of 1 mole of nitrogen and two moles of oxygen. What is the volume of the oxygen?
A. 3L
B. 2L
C. 8/3L

D. 4/3L
E. 1L
8. Which one of these molecules contains at least one double bond?
A. C
2
H
2
B. CO
C. CO
2
D. C
2
H
6
O
E. ICl
9. Which of the following elements displays the greatest metallic character?
A. As
B. Ga
C. Cl
D. Te
E. C
10. Which of the following compounds has the greatest boiling point?
A. C
2
H
6
B. CH
3
NH
2
C. CH
3
OH
D. CH
3
SH
E. C
2
H
2
11. Which of the following solutions shows the largest change in colligative properties?
A. 1m fructose C
6
H
12
O
6
B. 1m NaCl
C. 1m CaCl
2
D. 1m Na
2
S

E. 1m Na
3
PO
4
12. Which of the following pairs of substances is most likely to form an ideal solution upon mixing?
A. Water and sulfuric acid
B. Water and methanol CH
3
OH
C. Water and hexane C
6
H
14
D. Hexane and methanethiol CH
3
SH
E. Water and ammonia NH
3
Questions 13–15 refer to atoms of the following elements.
( a ) Lithium
( b ) Carbon
( c ) Nitrogen
( d ) Oxygen
( e ) Fluorine
13. In the ground state, have only 1 electron in each of the three p orbitals
14. Have the smallest atomic radius
15. Have the smallest value for first ionization energy
16. Which of the following species is NOT planar?
( a
) CO
3 2 –
( b
) NO
3
–
( c
) ClF
3
( d ) BF
3
( e ) PCl
3
17. The hybridization of the carbon atoms in ethane, C
2
H
6
can be described as
( a
) sp
( b
) sp
2
( c
) sp
3
( d ) dsp
2
( e ) d
2 sp
18. The half-life of 55 Cr is about 2.0 hours. The delivery of a sample of this isotope from the reactor to a certain laboratory requires 12 hours. About what mass of such material should be shipped in order that 1.0 mg of 55 Cr is delivered to the laboratory?
( a ) 130 mg
( b ) 64 mg
( c
) 32 mg
( d
) 11 mg
( e
) 1.0 mg

19. At constant temperature, the behavior of a sample of a real gas more closely approximates that of an ideal gas as its volume is increased because the
( a ) collisions with the walls of the container become less frequent
( b ) average molecular speed decreases
( c ) molecules have expanded
( d
) average distance between molecules becomes greater
( e
) average molecular kinetic energy decreases
20. A sealed vessel contains 0.200 mol of oxygen gas, 0.100 mol of nitrogen gas, and
0.200 mol of argon gas. The total pressure of the gas mixture is 5.00 atm. The partial pressure of the argon is
( a ) 0.200 atm
( b ) 0.500 atm
( c ) 1.00 atm
( d
) 2.00 atm
( e
) 5.00 atm
21. Which of the following accounts for the fact that liquid CO
2 is not observed when a piece of solid CO
2
(dry ice) is placed on a lab bench?
( a ) The phase diagram for CO
2 has no triple point.
( b ) The normal boiling point of CO
2 is lower than its normal freezing point.
( c ) CO
2
( s ) is a molecular solid.
( d
) The critical pressure for CO
2 is approximately 1 atm.
( e
) The triple point for CO
2 is above 1 atm.
22. If

G for a certain reaction has a negative value at 298 K, which of the following must be true?
I. The reaction is exothermic.
II. The reaction occurs spontaneously at 298 K.
III. The rate of the reaction is fast at 298 K.
( a ) I only
( b ) II only
( c ) I and II only
( d ) II and III only
( e ) I, II, and III
23. A mixture of gases containing 0.20 mol of SO
2 reacts to form SO
3 and 0.20 mol of O
2 in a 4.0 L flask
. If the temperature is 25ºC, what is the pressure in the flask after reaction is complete?
( a
) 0.4(0.082)(298)4atm
( b
) 0.3(0.082)(298)4atm
( c ) 0.2(0.082)(298)4atm
( d ) 0.2(0.082)(25)4atm
( e ) 0.3(0.082)(25)4atm
24. A sample of CaCO
3
(molar mass 100. g) was reported as being 30. percent Ca.
Assuming no calcium was present in any impurities, the percent of CaCO
3 in the sample is
( a
) 30% ( b
) 40% ( c
) 70% ( d
) 75% ( e
) 100%
2 Al( s ) + 6 HCl( aq )

2 AlCl
3
( aq ) + 3 H
2
( g )

25. According to the reaction represented above, about how many grams of aluminum
(atomic mass 27 g) are necessary to produce 0.50 mol of hydrogen gas at 25ºC and
1.00 atm?
( a ) 1.0 g
( b ) 9.0 g
( c
) 14 g
( d
) 27 g
( e
) 56 g
Experiment Initial [X] (mol L –1 ) Initial [Y] (mol L –1 ) (mol L –1 min –1 ) Initial Rate of Formulation of Z
1 0.10 0.30 4.0 X

10
–4
2 0.20 0.60 1.6 X 10
–3
3 0.20 0.30 4.0 X

10
–4
26. The data in the table above were obtained for the reaction X + Y

Z. Which of the following is the rate law for the reaction?
( a ) Rate = k [x] 2
( b ) Rate = k [y] 2
( c
) Rate = k [x][y]
( d
) Rate = k [x] 2 [y]
( e
) Rate = k [x][y] 2
A

X
27. The enthalpy change for the reaction represented above is

H
T
. This reaction can be broken down into a series of steps as shown in the diagram:
A relationship that must exist among the various enthalpy changes is
( a
)

H
( b
)
( c
)
( d
)
( e
)

H

H

H

H
T
–
T
+
3
– (
2
– (
T
+

H

H

H

H

H
1
–
1
+
1
+
3
+

H

H

H

H
2
=

H
2
–
2
+

H

H
2
) =

H
T
1
) =

H
T
1
+

H
3
= 0
3
= 0
3
28. What formula would be expected for a binary compound of barium and nitrogen?
( a ) Ba
3
N
2
( b ) Ba
2
N
3
( c ) Ba
2
N ( d ) BaN
2
( e ) BaN
29. Of the following organic compounds, which is least soluble in water at 298 K?
( a ) CH
3
OH, methanol
( b ) CH
3
CH
2
CH
2
OH, l-propanol
( c
) C
6
H
14
, hexane

7. C
8. C
9. B
10. C
11. E
12. B
2. E
3. D
4. C
5. A
6. B
13. C
14. E
15. A
16. E
17. C
( d
) C
6
H
12
O
6
, glucose
( e ) CH
3
COOH, ethanoic (acetic) acid
30. The molecular mass of a substance can be determined by measuring which of the following?
I. Osmotic pressure of a solution of the substance
II. Freezing point depression of a solution of the substance
III. Density of the gas (vapor) phase of the substance
( a
) I only
( b ) III only
( c ) I and II only
( d ) II and III only
( e ) I, II, and III
MC Answers:
1. A

18. B
19. D
20. D
21. E
22. B
23. B
24. D
25. B
26. B
27. A
28. A
29. C
30. E
FR:
1. 1.000g of a compound containing C,H, N, and O is burned. 1.24g of CO
2
, .1267g of H
2
O, .1966g of N
2 are obtained.
A. Find the empirical formula of the molecule.
B. The molecule is found to have a density of 6.495g/L at 400K and 1.000 atm pressure. Find the molar mass and the molecular formula of the molecule.
C. 2.00g of another unknown molecule with empirical formula C
3
H
4
O is dissolved in 50.00g of a solvent with a freezing point constant of 1.00C/m. The solvent's molar mass is 100.00g/mol. The freezing point of the solvent is lowered by .35695C. Find the molar mass of the unknown molecule.
D. In part C the chemists can make a number of mistakes in their lab procedure. If the chemists weigh the sample then spill some before adding it to the solvent, what effect will this have on the results?
E. If the chemists in part C measure a value for the freezing point depression that is smaller than the real value, what effect will this have on the results?
2. A. Consider the oxygen atom and the oxide ion O 2.

i. Which is attracted to a magnetic field? Explain. ii. Which is larger? Explain. iii. Which will have a more favorable (exothermic) electron affinity? iv. Write the electron configurations of both species v. Will it be easier to remove the first additional electron from the oxide ion or the second? explain.
B. Oxide has the same electron configuration as neon. Which is larger? Explain.
C-F Consider H
2
O, O
2
, and H
2
.
C. Which of these compounds has the strongest London dispersion forces? Explain.
D. Rank the compounds from highest to lowest boiling point. Explain.
E. What hybridization do the oxygen orbitals in water exhibit?
F. What is the hybridization of the orbitals in oxygen?
3. A chemist is studying these molecules: ethane, ethene, ethyne, ethanol, ethanal, and ethanoic acid.
Ethane: C
2
H
6
Ethene: C
2
H
4
Ethyne: C
2
H
2
Ethanol: C
2
H
5
OH
Ethanal: CH
3
CHO
Ethanoic acid: CH
3
COOH
A. Draw Lewis structures for the 6 compounds
B. Tell which compound has the shortest carbon-carbon bond and explain why.
C. Which compound has a higher boiling point, ethane or ethanol? Explain.
D. Explain why ethyne is nonpolar.
E. Which compound is more soluble in water, ethanol or ethene? Explain.
F. Which compound will have the highest molar enthalpy of combustion? Explain.

G. Draw arrows pointing to: i. a carbon with sp hybridization ii. an oxygen with sp 2 hybridization iii. an oxygen with no p orbitals iv. a trigonal planar carbon v. a tetrahedral atom
H. A sample of ethanol is boiled and then cooled and recondensed. An AP chem student says that the sample boiled when the bonds between C,H, and O were broken. Another student says this is wrong.
Their teacher offers them samples of isotopically pure ethanol, one with all of the hydrogen as protium
(hydrogen-1) and the other with all the hydrogen as deuterium (hydrogen-2). Design an experiment that could prove who is right and who is wrong about what is happening when ethanol boils.
I. Which carbon-carbon bond in the molecules in this problem has the largest bond dissociation energy?
Explain.
J. Ethyne reacts with oxygen to produce carbon dioxide and water. Predict the signs of delta H, delta S and delta G for this reaction. Explain.
K. A sample of ethene is held at room temperature mixed with oxygen. It does not react. A spark is applied and the ethene burns. An AP chemistry student says that is evidence that the reaction is endothermic. Critique this statement using your knowledge of chemistry.
L. An AP chemistry students says that when ethane is heated and decomposed to produce hydrogen and carbon the reaction is endothermic because bonds were broken. Another students says this can't be true because the carbon formed graphite, which has bonds and the hydrogen forms H
2
which also has bonds. Explain why the decomposition of ethane is endothermic despite the fact that bonds are made when graphite and hydrogen form.
4. A mixture of copper and zinc is found. It turns out that the two elements are not alloyed, they are just a mixture. A chemist decides to analyze 1.00g of the mixture. The chemist adds 2.00g of HCl, which reacts with the zinc, but not the copper. The chemist adds HCl until no more bubbling is observed. The mixture is filtered and the copper is collected. The copper is weighed and .500g are obtained. The chemist wants to obtain the zinc so they neutralize the acid and reduce the zinc with aluminum foil.
A. How much aluminum is needed to neutralize the excess HCl? 2Al + 6HCl = 2AlCl
3
+ 3H
2
B. How much Al is needed to react with the zinc? 2Al + 3Zn 2+ = 2Al 3+ + 3Zn

C. The chemist decides to clean some tarnish off of another 1.00g sample of copper. They add acid to the copper and clean the tarnish off. Assume that tarnish is copper carbonate and all of it is removed by the acid. After cleaning the copper the mass is .99g. What was the amount of copper in the piece before it tarnished?
D. The chemist finds a sample of sterling silver This is an alloy of silver and copper. They dissolve the sample in nitric acid, then neutralize it and add NaCl. The NaCl precipitates the silver as AgCl. A 1.00g sample of the alloy gives 1.25g of AgCl. What is the percentage of silver in the original sample of sterling silver alloy?
5. See 2011 AP chem free response form A #3.
6. See 2010 AP chem free response form A #2.
7. A chemist takes 1.00L of aqueous H
2
O
2
solution. The solution is placed in contact with a piece of silver. This silver catalyst decomposes the peroxide to water and oxygen gas. The chemist finds that
50.00ml of oxygen gas are produced by the peroxide solution.
A. Find the molarity of the peroxide solution. The experiment was conducted at 27.0C and 750 torr. At this temperature the vapor pressure of water is 26.7 torr. Assume the peroxide solution has a density of
1.00g/ml.
B. Explain why an old bottle of peroxide is less effective at cleaning wounds than a new bottle.
C. How does the silver increase the rate of the decomposition of peroxide?
D. Some 1.00M peroxide is reacted with iodide ion. This forms triiodide ion, I
3
and water. Draw a Lewis structure for this ion.
8. A chemist wants to find the molar mass of an unknown liquid. They take a 500.00ml Erlenmeyer flask, weigh the flask and get a mass of 100.00g. They have a cap for the flask. The cap has a valve that allows the passage of gas between the flask and the atmosphere. The cap has a mass of 25.00g. The chemist adds some amount of the unknown liquid to the flask and caps the flask. The valve is opened and the flask is heated until no liquid is visible. The gas in the flask is mostly the vapor of the unknown liquid with little air. The valve is closed and the flask is cooled so that the vapor condenses to a liquid.
After the flask is cooled the valve is opened and closed quickly to admit air into the low pressure of the flask. The flask is then weighed and the mass of the flask, cap, and vapor, are found to be 135.00g.
Inserted into the cap is a thermometer in addition to the valve. While the liquid was boiling the temperature was measured and the value 80.0C was recorded. The atmospheric pressure in the lab was
1.000 atmospheres.
A. Find the molar mass of the unknown liquid.
B. What effect will not boiling all the liquid have on the results?

C. What effect will boiling the liquid too long and having a mixture of vapor and air in the flask have on the results?
D. What effect will not letting air into the flask have on the results?
9. 2.70g of aluminum are added to excess HI. The hydrogen produced by the reaction is collected at
300.00K and 1.000atm pressure. At this temperature the vapor pressure of water is 26.7 torr.
A. What volume of wet hydrogen will be collected?
B. What volume of dry hydrogen is collected?
C. If the experiment were performed by a group of students who collected 2.30L of wet hydrogen calculate the molar volume of dry hydrogen at these conditions.
D. In part C the students did not get the correct answer, which can be calculated from the answer to A.
What errors could have caused their results to be in error?
10.
A. An unknown gas is collected over water. 50.00ml of gas is collected a 300.00K and 1.000atm. The vapor pressure of water at this temperature is 26.7 torr. The mass of the gas collected is .2500g. Find the molar mass of the gas.
B. It turns out that the molar mass of the gas is lower that what is measured in part A. What errors could have caused this?
11.
A chemist finds some materials. They perform experiments and find the following results:
Material
Melting point
Malleability
Appearance
Conductivity
Electrolyte
A
High
Brittle
Dull
Low
No
B
High
Brittle
Dull
Low
Yes
C
High
Malleable
Shiny
High
No
A. Explain which type of bonding each material exhibits. Justify your answers.
D
Low
Brittle
Dull
Low
No
B. Which two materials bond by sharing electrons between a finite number of electrons? Explain the difference in properties of these two materials with your knowledge of bonding.

C. Some students say that the bonding in B is weak because it dissolves easily in water. Explain why they are wrong and explain why they think what they think. Use thermodynamics in your answer.
12. A hydrated ionic substance is heated by some chemists. 2.50g of the substance decrease to 1.65g after the first heating, 1.60g after the second, and 1.60 after the third. The anhydrous substance is then added to 100.00g of water. The freezing point of the water is lowered to -.372C. The chemists doing the experiment know that the ionic compound's van't Hoff factor is 2.
A. Find the molar mass of the anhydrous salt
B. Find the formula of the hydrate
C- Tell what effect each of these mistakes would have on the results:
C. The chemist let the substance sit out and absorb water from the atmosphere before he weighed it.
D. The chemist let the substance sit and absorb water after he heated it.
E. The chemist overheated the salt, decomposing it and driving off a gas.
F. The chemist didn't heat the salt long enough and didn't drive off all the water
G. The chemist spilled some salt between the original weighing and putting it into the crucible to heat it.
H. The chemist spilled some salt between the heating and weighing.
I. The chemist spilled some anhydrous salt between weighing it and putting it into the distilled water to take the freezing point.
J. The chemist made a mistake and the 100.00g of water was actually 99.00g of water.
K. The chemist made a mistake and the temperature of freezing was greater than what they measured.
13. A chemist adds iodine dissolved in methanol to some solid zinc. There is a reaction and the chemist recovers solid zinc and an ionic compound dissolved in the methanol. The methanol is poured off and the zinc is separated from the methanol. The methanol is boiled away and a hygroscopic compound is recovered. Hygroscopic compounds absorb water from the air. The chemist originally used 1.00g of zinc and 1.00g of iodine. They recover .75g of zinc and 1.05g of the solid hygroscopic compound.
A. Calculate the empirical formula of the compound using the amount of zinc consumed, assuming all iodine was consumed.
B. Calculate the empirical formula of the compound using the amount of hygroscopic compound produced and the amount of zinc consumed.

C. Calculate the empirical formula of the compound assuming all iodine was consumed and the mass of hygroscopic compound produced.
D. The compound produced is zinc iodide. Zinc most commonly adopts a 2 + ion in ionic compounds.
Using your knowledge of atomic structure and bonding predict the formula of zinc iodide.
E. Which of the three methods of calculating the empirical formula of zinc iodide was the most accurate? Explain why it was the most accurate using your knowledge of lab techniques.
F. Another chemist wishes to find the empirical formula of copper iodide. They plan on heating solid copper with solid iodine and subliming the iodine which will then react with the copper. What is the best way for them to do the lab? What data should they gather and what calculations should they perform?
G. The chemists who made zinc iodide want to do an error analysis. They want to know what effect these mistakes would have on their results: i. The zinc solid has measurable traces of zinc iodide stuck to it when they calculate using the method in
A. ii. The zinc solid has measurable traces of zinc iodide stuck to it when they calculate using the method in
B. iii. The zinc solid has measurable traces of zinc iodide stuck to it when they calculate using the method in C. iv. The hygroscopic compound absorbed water when they calculated using the method in A. v. The hygroscopic compound absorbed water when they calculated using the method in B. vi. The hygroscopic compound absorbed water when they calculated using the method in C. vii. The chemists spilled some of the hygroscopic compound when they calculated using the method in
A. viii. The chemists forgot that iodine is diatomic when they did their calculations in A. Maybe you forgot also. Now you need to see if it matters.
14.
Experiment
1
2
3
4
[A]
1M
2M
2M
10M
[B]
1M
1M
2M
5M
Initial Rate
1Ms -1
2Ms -1
8Ms -1

A. What is the overall order of the reaction? Justify your answer.
B. Find k for the reaction, including units.
C. Find the rate of reaction 4.
D. Is it likely that the reaction occurs in one elementary step? Explain.
FR Answers:
1. A. C
2
HNO
2
B. 213.06g/mol, C
6
H
3
N
3
O
6
C. 112.06g/mol
D. Molar mass is too high
E. Molar mass is too high
2. A i. oxygen atom is attracted to a magnetic field because it is paramagnetic ii. Oxide ion is larger because it has more electrons that are held with the same number of protons iii oxygen atom has an exothermic electron affinity while the oxide ion's is endothermic. An oxygen ion with one extra electron, O-, also has an endothermic electron affinity. Don't give low level weak answers like:
"Oxygen wants to be a noble gas."
"Oxygen wants 8 electrons."
"Having 8 valence electrons is stable so oxide will not add another electron."
The question was why one was more favorable than the other. The oxygen atom has fewer electrons and adding an electron to an electronegative atom like oxygen is likely to be exothermic. Regardless, the oxide ion will have more repulsion than the oxygen atom so it will be more favorable (exothermic). iv. Atom: 1s 2 2s 2 2p 4 Ion: 1s 2 2s 2 2p 6 v. The second electron is easier to remove (lower ionization energy) than the first because of repulsion and the size of the ion.

B. Oxide is larger because it has 2 fewer protons than the neon.
C. O
2 has the strongest dispersion forces because it is the most polarizable due to its larger size and number of electrons.
D. H
2
, O
2
, H
2
O. The first two have dispersion forces and O2 is stronger because it is more polarizable as it is larger. Water has hydrogen bonding which is stronger than dispersion forces.
E. sp 3
F. sp 2
3.
A.
B. Ethyne has the shortest bond because it is a triple bond
C. Ethanol has hydrogen bonding while thane only has dispersion forces.
D. Don't say that the C-H bond is nonpolar because it isn't. Draw a picture and show how the molecule is symmetrical.
E. Ethanol because it has hydrogen bonding
F. Ethane because it forms the largest number of moles of water and carbon dioxide. It is higher than ethanol because ethanol is partially oxidized.
G. The students should boil a mixture of deuterated ethanol and ethanol with protium only, then recondense it. They then check to see the molar mass of the liquid molecules. If bonds are broken during boiling then the products will have a variety of masses. This is because the carbon, oxygen, protium and deuterium would rearrange themselves randomly while recondensing. If hydrogen bonds were disrupted during boiling then the liquid molecules will have the same masses as before. NO

MATTER HOW MANY TIMES WE GO OVER THIS SOME STUDENTS STILL THINK BONDS ARE BROKEN
DURING BOILING.
I. Ethyne's triple bond is the strongest
J. Delta H is negative, delta S is positive and delta G is negative. Delta H is negative as the reaction is an example of combustion. Delta S is positive because more moles of gas are produced than are consumed. Delta G must be negative because of the signs of the other 2 processes since Delta G = Delta
H - T Delta S.
K. The spark is to provide activation energy to start the reaction. The need for the spark says nothing about the delta H of the reaction.
L. In order to break ethane into carbon and hydrogen atoms energy is required to break the bonds in the molecule. Some energy is released when graphite is formed from the carbon and H
2
is formed from the hydrogen atoms. The amount of energy required to decompose ethane is more than the energy released when the graphite and H
2
form.
4.
A. .368g
B. .138g
C. Add the .99g of copper in the sample to the mass of copper in the .01g of copper carbonate (.005g).
.995 g of Cu in the original.
D. 94.1%
5. See college board website
6. See college board website
7.
A. .0019 mol of O
2
produced so the molarity is .0019 since we used a liter of solution
B. The peroxide decomposes over time.
C. Silver lowers the activation energy for the reaction.
D. 3 lone pairs on the terminal I atoms, 3 on the middle I.

8.
A. 578.92g
B. Molar mass too high
C. Molar mass to low
D. Molar mass to low
9.
A. 2.46L of H
2
at that pressure but there is some water as well. I got 2.58L by using .9517atm as the pressure.
B. 2.46L
C. 2.19L
D. The most likely error is bubbles of hydrogen missing the collection tube
10.
A. 129.24g/mol
B. The most likely error is bubbles of gas missing the collection tube.
11.
A. Substance A is network covalent, B is ionic, C is metallic, and D is molecular covalent
B. A and D have covalent bonding. They have different properties because bulk D is held together by hydrogen bonding, dipole-dipole forces or dispersion forces while A is held together by covalent bonding.
C. Ionic compounds are held together by electrostatic attraction. This is a strong force. However, when some ionic compounds are added to water the water molecules can attract ions. The enthalpy of hydration can be higher than the lattice energy. In this case it is favorable, from the standpoint of enthalpy, for the compound to dissolve. With regards to entropy it is favorable for the ionic crystal to be broken up. It is unfavorable when the water molecules organize around the ions in solvation shells.
12.
A. 160g

B. 5 waters
C. Number of waters too high
D. Number of waters too low
E. Number of waters too high
F. Number of waters too low
G. Number of waters too high
H. Number of waters too high
I. Molar mass of the salt too high, number of waters too high
J. Molar mass of the salt too low, number of waters too low
K. Molar mass is too low, number of waters is too low
13.
A. ZnI
2.05
B. ZnI
1.64
C. ZnI
10.23
D. ZnI
2
E. It is much easier to recover and wash a solid metal than to recover a substance that was dissolved in a liquid. The fact that the substance is hygroscopic makes it even harder to get an accurate mass for the zinc iodide product.
F. The chemist who wants to produce copper iodide should add solid copper to solid zinc and heat the mixture. The iodine will sublime and react with copper. The copper should be washed and the empirical formula calculated from the mass of copper. The copper iodide could be isolated if desired. There should not be a calculation based on iodine consumed since much iodine will be lost to sublimation.
G. i. Mass of zinc consumed is too small, number of moles of zinc too low, number of iodine too high in formula. ii. Mass of zinc consumed is too small, mass of zinc iodide produced is too small, number of iodine is too high in formula

iii. The mass of zinc iodide produced is too small so the mass of zinc consumed is too small, so the moles of iodine in the formula is too small iv. No change v. Amount of iodine consumed is too high so the number of iodines in the formula is too high vi. Amount of zinc consumed is too high and the number of iodines in the formula is too low vii. No change viii. It doesn't matter
14. A. Third since A is first order and B is second order
B. k = 1L 2 mol -2 s -1
C. 250Ms -1
D. No, because it is unlikely that three molecules can collide at once in the proper orientation and with sufficient energy to react.