AP chem 2013 Multiple Choice

{22} NaOH(aq) + HCl(aq) -> NaCl(aq) + H2O(l) To determine the concentration of a NaOH(aq) solution, a student titrated a 50 mL sample w/ .1 M HCL. The Reaction is presented in equation above. Titration is monitored using a pH Meter, and the experimental results are plotted in the graph below

A

{25} a student mixes a 10.0 mL sample of 1.0 M NaOH w/ a 10.0 mL sample of 1 M HCL in a polystrene container. The temperature of the solutions before mixing was 20.0C. If the final temperature of the mizture is 26.0C, what is the expiremental value of [d]H*rxn? (specific heat = 4.2 J/(g*K) and a density of 1.0 g/mL A) -50 Kj/mol B)-25 kJ/mol C) -5e4 kJ/mol D)-5e2 kJ/mol``

A

{3}A sample of a hard, solid binary compound at room temperature did not conduct electricity as a pure solid but became conductive when dissolved in water. Which of the following types of interactions is most likely found between the particles in the substance? A) iconic bonds B) Metallic Bonds C) Covalent bonds D) hydrogen bonds

A

{40} {Bond = H-H; Bond Energy = 430 kJ/mol} {Bond Cl-Cl; BE = 240 kJ/mol} {Bond H-CL; BE = 430 kJ/mol} Based on the bond energies shown in the table above, which of the following diagrams best represents the change in energy as the reaction below proceeds (see picture

A

{42} 2 H2S(g) + CH4(g) <--> CS2(g) + 4H2(g) Kc = 3.4 E-4 A 0.10 mol sample of each of the four species in the reaction represented above is injected into a rigid, previously evacuated 1.0 L container. Which of the following species will have the high concentration when the system reaches equilibrium? A) H2S B) CH4 C) CS2 D) H2

A

{47} Which of the following statements abouth the bonds in the reactants and products is most accurate A) the sum of the bond of ofbox in the product b) the sum of the bond enthralpies is greater than the sum of bond enthralpies of harmonics C) The length of the bond btwn CArbon and Oxygen in CH3OD is shortee than the length is shorter than the rank between carbon and oxygen in CO D) All of the bonds are in rxn and are polar

A

{5}Which of the Following arranges molecules in order of bond enthalpies: A) F2<O2<n2 B)O2<N2<F2 C)N2<O2<F2 D)N2<F2<O2

A

{7}Electronegativity table: H-2.1 C-2.5 S-2.5 F-4.0 Cl-3.0 Si-1.8 Which of following arranges molecules in order of bond polarity A)CH4<SiCl4<SF4 B)CH4<SF4<siCl4 C)SF4<CH4<SiCl4 D)SiCl4<SF4<CH4

A

{6}Based on Coulomb's law and Info in parens. in pictures which of the following cations is most likely to have the weakest interaction with an adjacent water molecule in an aqueous solution A) Li+ (Ionic radius, 60pm) B)Na+ (95pm) C)Ca 2+ (99pm) D)In 3+ (81 pm)

B

{14} H2O2(aq) -> 2 H2O(l) + O2 (g) E* = .55 v THe equation and standard cell potential for the decomposition of H2O2 in acidic solution at 25* is given above. The reduction half-reactions for the process are listed below: O2(g) + 4 H+(aq) + 4 e- -> 2 H2O(l) E* = 1.23 O2 + 2 H+(aq) + 2 e- -> H2O2 E* = ? What is the reduction potential for the half reaction represented above? A) -1.78 V B) -.68 V C) + 6.8 V D) +1.78 V

C

{18} At room temperature I2 is a molecular Solid. Which of the following provides a characteristic of I2 with a correct explanation A) It has a high melting point because it has weak inter molecular forces B) It is hard because it forms a three dimensional covalent network C) it is not a good conductor of electricity, because its valence electrons are localized in bonding and non-bonding pairs D) It is very soluble in water because its molecules are polar

C

{29}(see image) Aprox. How long did it take for 75% of the initial amount, C25H30N3+ to react A) 75s B) 225 s C) 300 s D) 600 s

C

{31} TO choose a wavelength to analyze the progress of a reaction, a student records the absorbance spectra of both C25H30N3+ and C25H30OH in the range 200-800nm. The two spectra are resented in graph below(see pictures) The studetn wants to use the spectrophotometer to measure [C25H30N3+] with the greatest sensitivity as the reaction progresses. Which of the followng indicates the best wavelength setting and explains why it is best A) 205 nm, the colorless form of the molecule will absorb significantly at this wavelength B) 205 nm, because both forms of the molecule will absorb significantly at this wavelength C) 590nm, because only the violet form of the molecule will absorb significantly at this wavelength D) 590, because this wavelength falls in the violet region of the visible light spectrum

C

{37} Two Trials are rin, usng excess water. In the first trial, 7.8 g of Na2O2(s) (mm 78g/mol) is mixed with 3.2 g of s(s). THe NaO2 and S(s) react as completely as possible. Both Trials yield the same amounf of SO2. Whihc of the following identifies the limiting reactant and the heat released, q, for the two trials at 298k A) {LR = S; q = 30 kj} B) { LR = S; q = 61 kJ} C) {Lr=Na2O2; q=30 kJ} D) {Na2O2; q=61kJ}

C

{39} Which of the following statements about the thermodynamic favorability of the reaction at 298 k is correct A) it is unfavorable B) it is favorable and is driven by [d]S* C) It is favorable and driven by [d]H* only D) It is favorable and driven by both [d]h* and [d]S*

C

{41} See picture A) XO2 B) X2O C) X2O3 D) X2O5

C

{44} CH3OH -> CO + 2H2 [d]H = 91 kj/mol what happens to temperature of the contents of the vessel As the rxn occurs A) Temperature must increase, because acordinf to Le Chateliers principle, an increase in temp causes more products to form B) The temperature must decrease,, because the reaction takes place at a temperature above room tempreature C) The temperature must decrease, because the rxn is endothermic D) the temperature does not change, because the vessel is insulated

C

{46} what can be infered about [d]S* for the reaction at 600K A) it must be positive, since the reaction is unfavorable at 600k B) It must be negitive, since there are more mols of product than reactant C) It must be positive, since [d]G* is - and [d]H* is positive D) It must be negitive, sing [d]G is positive and [d]H is positive

C

{8}X(g) —>X+ + e- IE 740 kJ/mol X+ —> X2+ + e- IE 1450 kJ/mol X2+ —> X3+ + e- 7730 kJ/mol Explain difference btwn 2nd and 3rd ionizations A) Effective nuclear charge decreases with successive ionizations B)Sheilding of outer electrons increases with successive ionizations C) The electron removed durring the third ionization is, on average, much closer to the nucleus than the first two electrons were D) ironic radius increases with successive ionizations

C

{23} One Student titrated the NaOH with .1M HCL(aq) instead of .1 M HCL. How would the students titration curve differ from the original curve A) initial PH would be 11 instead of 13 B) The pH at eq point would be 5 instead of 7 C) the PH far beyond the eq point would be higher than in original curve D) The pH far beyond the eq point would be lower than in original curve

D

{2}Which of the following helps explain why an increase in temperature increases the rate of chemical reaction: A) at higher temps, rxns have lower Activation energy B)At higher temps, rxns have a higher activation energy C) At higher temperatures, every collision results in the formation of the product D) At higher temperatures, high energy collisions happen more frequently

D

{35} The photoelectron spectra of the 1s electron of two isoelectronic species, Ca 2+ and AR, are shown above. Which of the following correctly identifies the species associated with peak X and provides valid justification A) Ar, Because it has completly filled energy levels B) Ar, Because its radius is smaller than the radius of Ca2+ C) Ca2+, because its nuclear mass is greater than that of Ar D) Ca2+, Because it's nucleus has two more protons than the nucleus AR has

D

{36} A vessel contains Ar(g) at a high pressure. Which of the following statements is significantly greater than the pressure calculated using the ideal gas law A) The Molar mass of Ar is relatively large B) A significant number of Ar2 Molecules form C) The attractive forces among Ar atoms cause them to collide with the wall of the container with less force D) The large and combined volume of the At atoms is too large to be negligable comapted with the total volume of the container

D

Important equation:

N2(g) + 3 H2(g) <->2 NH3. ΔH<0

{12}PbCl2. 1.2E-5 CuCl. 1.6E-7 AgCl. 1.8E-10 Hg2Cl2. 1.4E-18 Based on Ksp values above, a sat. Solution of which of the following has highes [cl-] A)PbCl2 b)CuCl C) AgCl D)Hg2Cl2

A

{13}Look at question 13

A

{20} HX(aq) + Y-(aq) <-> HY + X- Keq > 1 Based on the information given above, which of the following is the strongest acid A) HX B) Y- C)HY D) X-

A

{11}23.0 sample of a compound contain 12.0 g of C, 3.0 g of O. Which of the following is the empirical formula of the compound A)Ch3O b) C2H6O C) C3H9O2 D) C4H12O2

B

{16} C2H4(g) -> C2H6(g) which of the following will most likely increase the rate of the reaction represented above? A)Decreasng the temperature of the rxn system B) Adding heterogeneous catalyst to the rxn system C) Increasing the volume og the reaction vessel using a piston D) Removing some H2 from teh rxn system

B

{17} Which of the following molecules is least soluble in water( see picture

B

{19} CS2(l){ 76 g/mol; Boiling point = 46.5C;} CCl4(l){154 g/mol; BP = 76.7C;} Based on above info, which liquid CS2 of CCl4 has the higher equilibrium vapo pressure at 25C and why? A) CS2(l) because it has stronger LDFS B) CS2(l) because it has weaker LDFS C) CCl4(l), becuase it has stronger LDFS D) CCl4 becuase it has stronger LDFs

B

{26} 2 NO2(g) + F2(g) -> 2 NO2F(g) The rate law for the reactin represented by the equation above is rate = k[NO2][F2]. Which of the following could be the first elementary step of a 2 step mechanism for the reaction if the first step is slow and the second step is fast A) F2(g) - 2F(g) B) NO29g) + F2(g) -> NO2F(g) + F(g) C) NO2(g) + F(g) -> NO2F(g) D) 2NO2(g) + F2(g) -> 2 NO2F(g)

B

{27} Which of the following Lewis Electron-dot diagrams represents the molecule that contains the smallest bond angle (see image)

B

{28}A mixture containing equal number of ethyl acetate and butyl acetate was separated using distillation. Based on the diagrams shown above, which of the following identifies the substance that would be initially present in higher concentration in the distillate and correctly explains why that occurs. (see image) A) Ethyl Acetate, because it has fewer C-C bonds to break B) Ethyl Acetate, Because it has shorter carbon chain and weajer LDFs C) Butyl acetate, because it has more C-C bonds to break D) Butyl Acetate, because it has a longer carbon chain and weaker dipole-dipole attractions

B

{30} What would be the reaction rate if the solution C25H30N3+ is diluted by a factor of 2: A) it would be higher B) it would be lower C) it would not change D) it would initially be higher but rapidly decrease

B

{34} The pH of a 0.01 M HNO2 solution is in which of the following ranges (Ka = 4.0e-4) A) btwn 1 & 2 B) btwn 2 & 3 C) Btwn 4 & 5 D) Btwn 6 & 7

B

{43} At 1 atm a smaple of ice is heated to liquid water and then to water vapor. The heating curce is shown above(in pictures). Which of the following lists the sign for the changes in enthralpy and entropy for the process corrosponding to segment X, going from left to right | [d]H | [d] S A) | + | - B) | + | - C) | - |- D) | - |+

B

{Vol of .1M HCl = 50 ml; vol of .1M NaOH = 50 ml; Heat Released = X} {Vol of .1M HCl = 100mL; vol of .1M NaOH = 50 ml; Heat Released = Y} A student conducted an experiment to determine [d]H*rxn for the rxn btwn HCl & NaOH. The Student ran two trials using the volumes of HCl & NaOH indicated in the table above, and determined the amount of heat released. Which of the following best explains the relationship btwn X&Y A) Y = 2X, as volume of HCl used in trial 2 is twice teh volume used in trial 1 B) Y=X because # of mols of acid and base reacting with each oother is the same in both trials C) Y = (2X)/(3) because heat is distributed over more particles in trial 2 than trial 1 D) Cannot be predicted

B

{10}Two samples of MG of equal mass were placed into equals amounts of HCL contained in two separate reaction vessels. Particle representations of the mixing of MG and HCL in the two reaction vessels are shown in Fig 1 and Fig 2 above. Water Molecules are not included in particle representation. Which of the reactions will proceed faster and why(see diagram for q10) A) Rxn in Fig 1, because the atoms of Mg are more concentrated than those in fig 2 B) The reaction in fig 1, because the Mg in Fig 1 has a larger mass than the Mg in Fig 2 C) The reaction in Fig 2, because more Mg atoms are exposed to HCL in Fig 2 than in Fig 1 D) The reaction in Fig 2, because Mg in FIg 2 has less surface area than MG in fig 1

C

{15} Which of the following is true for the decomposition of H2O2(see previous) A) [d]G* > 0 && Keq > 1 B) [d]G* > 0 && keq < 1 C) [d]G* < 0 && keq > 1 D) [d]G* < 0 && keq < 1

C

{32} CO{g) + H2O(g) <-> CO2(g) + H2(g) Kc = 1.5e3 A 2.0 Mol sampl eof CO(g) and a 2.0 mol sample of H2O(g) are introduced into a previouslt evacuated 100 L rigid container, and the temperature is held constant as the rxn represented above reaches equilibrium, Which of the following is true at equilibrium A) [H2O]>[CO] && [CO2]>[H2] B) [H20]>[H2] C)[CO2]>[CO] D) [CO]=[H2O]=[CO2]=[H2]

C

{33} {Compound = Ag2SO4; Ksp@298k = 1e-5} {Compound = PbSO4; Ksp@298k = 1e-8} A 1L solution of AgNo3 and Pb(NO3)2 has an Ag+ concentration of .020M and a Pb2+ concentration of .001M. A .001 mol sample of K2SO4(s) is added to the solution. Based on teh information above, which of the following will occur A) No Precipitate will form B) Onlt Ag2SO4 will precipitte C) Only PbSO4 will precipitate D) Both Ag2SO4 and PbSO4 will precipitate

C

{38} Atoms of which element are reduced int he reaction? A) S; each atom loses 4 electrons B) Na in Na2O2; Each atom loses an electron C) O in Na2O2; each atom gains one electron D) o in H2O, each aatom gains an electron

C

{9}A student preforms an acid base titration and plots the experimental results in the graph above(titration curve where equivalence point begins at 7ph and 25 ml, look at graph for q 9). Which of the following statements best explains the exipamental findings: A) A strong acid was titrated with a strong base, as evidenced by eq poin at PH = 7 B)A strong acid was titrated with a strong base, as evidenced by eq point at pH > 7 C) A weak acid was titrated with a strong base, as evidenced by equivalence point at pH > 7 D) A weak acid was titrated with a weak base, as evidenced by eq point at pH ~7

C

{1}In which of the following liquids do the intermolecular force include dipole-dipole forces: 1) F (l) 2) CH4 (l) 3)CF4 (l) 4) CH2F2 (l)

D

{21} AgNO3(aq) + NaCl(aq) -> AgCl(s) + NaNo3(aq) A student preforms an analysis to determine the amount of AgNo3 in a solution. Excess NaCl was added to the solution and the Ag+ preciptated as AgCl(s). The precipitate was collected by gravity filtration and dried in an oven. Three trials were preformed, and in each cas, according to the instructor, the mass of the precipitate recovered was 5% higher than actual mass of AgCl(s) that should have formed. WHich of the following account for this error A) Pores in filter paper were too large B) Not all the precipitate was transferred to the filter paper C) The NaCl solution was too concentrated D) the Precipitate was not rinsed with deionized water before drying

D

{45} A sample of CH3OH is placed in the previously evacuated vessel with a pressure of p1 @ 600K. What is the final pressure in the vesel after the reation is complete and contents return to 600K A) P1/9 B)P1/3 C) P1 D) 3P1

D

{48} { Acid = X. COncentraition = 0.05M, PH = 2.3} {Acid = Y, Concentration = 2.0 M, Ph = 2.8} {Acid = Z, 3.0 M, 2.8} Which of the following correctly ranks the three monoproctic acids from weakest to strongest: A) X<Y<Z B) X<Z<Y C) Z<Y<X

D

{4}NH3 was synthesized at 200C in presence of a powdered Os catayst, leading to the equilibrium system represented above. Which of the following changes would result in more NH3 in the mixture after equilibrium is re-established A) Replacing powdered Os with a solid cube of OS of the same total mass B) increasing the temperature of the system to 250C at a constant pressure C) Removinf H2 D) Adding some N2

D

{50} Fe + 2 HCL -> FeCl2 + H2 When a student adds 30 mL of 1 M HCl to .56 g of powdered Fe, a reaction occurs according to the equation above. Wen the reaction is complete, which of the following is true A) HCL is in excess, and .1 mol HCL is unreacted B) HCl is in excess, and .02 mol of HCl unreacterd C) .015 mol of FeCl2 has been produced D) .22 L of H2 has been produced

D

{Element, Oxides} {H; H2O, H2O2} {Li; Li2O, Li2O2} {Na; Na2O, Na2O2, NaO2} K, K2O, K2O2, KO2 {49} Based on info above, which is the best ypothesis reguarding oxide formed by Rb A) Rb will form only Rb2O B) RB will Form only RBO2 C) Rb will form only Rb2O and Rb2O2 D) Rb will form Br2O, Rb2O2, and RbO2

D