AP Chem
Semester 1 Review
1. When the following equation is balanced with whole number coefficients the sum of the coefficients is
CH3NH2 + O2 = CO2 + H2O + N2
A. 29
B. 14
C. 15
D. 37
E. 57
2. CH4 + O2 = CO2 + H2O
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. C2H2
B. CO
C. CO2
D. C2H6O
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. C2H6
B. CH3NH2
C. CH3OH
D. CH3SH
E. C2H2
11. Which of the following solutions shows the largest change in colligative properties?
A. 1m fructose C6H12O6
B. 1m NaCl
C. 1m CaCl2
D. 1m Na2S
E. 1m Na3PO4
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 CH3OH
C. Water and hexane C6H14
D. Hexane and methanethiol CH3SH
E. Water and ammonia NH3
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) CO32 –
(b) NO3–
(c) ClF3
(d) BF3
(e) PCl3
17. The hybridization of the carbon atoms in ethane, C2H6 can be
described as
(a) sp
(b) sp2
(c) sp3
(d) dsp2
(e) d2sp
18. The half-life of 55Cr 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 55Cr 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 CO2is not observed when a
piece of solid CO2(dry ice) is placed on a lab bench?
(a) The phase diagram for CO2has no triple point.
(b) The normal boiling point of CO2is lower than its normal freezing point.
(c) CO2(s) is a molecular solid.
(d) The critical pressure for CO2is approximately 1 atm.
(e) The triple point for CO2is 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 SO2and 0.20 mol of O2 in a 4.0 L flask
reacts to form SO3. 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 CaCO3 (molar mass 100. g) was reported as being 30. percent Ca.
Assuming no calcium was present in any impurities, the percent of CaCO3 in the
sample is
(a) 30% (b) 40% (c) 70% (d) 75% (e) 100%
2 Al(s) + 6 HCl(aq) 2 AlCl3(aq) + 3 H2(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 X10–4
2 0.20 0.60 1.6 X 10–3
3 0.20 0.30 4.0 X10–4
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 ∆HT. 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) ∆HT – ∆H1 – ∆H2 – ∆H3 = 0
(b) ∆HT + ∆H1 + ∆H2 + ∆H3 = 0
(c) ∆H3 – (∆H1 + ∆H2) = ∆HT
(d) ∆H2 – (∆H3 + ∆H1) = ∆HT
(e) ∆HT + ∆H2 = ∆H1 + ∆H3
28. What formula would be expected for a binary compound of barium and nitrogen?
(a) Ba3N2 (b) Ba2N3(c) Ba2N (d) BaN2(e) BaN
29. Of the following organic compounds, which is least soluble in water at 298 K?
(a) CH3OH, methanol
(b) CH3CH2CH2OH, l-propanol
(c) C6H14, hexane
(d) C6H12O6, glucose
(e) CH3COOH, 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
2. E
3. D
4. C
5. A
6. B
7. C
8. C
9. B
10. C
11. E
12. B
13. C
14. E
15. A
16. E
17. C
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 CO2, .1267g of H2O, .1966g of N2 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 C3H4O 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 O2-.
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 H2O, O2, and H2.
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: C2H6
Ethene: C2H4
Ethyne: C2H2
Ethanol: C2H5OH
Ethanal: CH3CHO
Ethanoic acid: CH3COOH
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 sp2 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 ofisotopically 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 H2 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 = 2AlCl3 + 3H2
B. How much Al is needed to react with the zinc? 2Al + 3Zn2+ = 2Al3+ + 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 H2O2 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, I3- 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 / A / B / C / DMelting point / High / High / High / Low
Malleability / Brittle / Brittle / Malleable / Brittle
Appearance / Dull / Dull / Shiny / Dull
Conductivity / Low / Low / High / Low
Electrolyte / No / Yes / No / No
A. Explain which type of bonding each material exhibits. Justify your answers.
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.