L3-37

An advertisement for a commercial hand warmer claims that the hand warmer works because a chemical reaction in the hand warmer draws out the body's own natural heat, causing a warming effect. Which of the following states the accuracy of the claim in the advertisement and best provides a correct scientific justification of the claim? A) The advertisement's claim is inaccurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was endothermic, which would cause the hands to feel colder. B) The advertisement's claim is inaccurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was exothermic, which would cause the hands to feel colder. C) The advertisement's claim is accurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was endothermic, which would cause the hands to feel warmer. D) The advertisement's claim is accurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was exothermic, which would cause the hands to feel warmer.

A) The advertisement's claim is inaccurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was endothermic, which would cause the hands to feel colder.

N2(g) + 3 H2(g) ⇄ 2 NH3(g) ΔH∘298 = -92 kJ/mol rxn ΔG∘298 = -33 kJ/molrxn Consider the reaction represented above at 298 K. When equal volumes of N2(g) and H2(g), each at 1 atm, are mixed in a closed container at 298 K, no formation of NH3(g) is observed. Which of the following best explains the observation? A) The N2(g) and the H2(g) must be mixed in a 1:3 ratio for a reaction to occur. B) A high activation energy makes the forward reaction extremely slow at 298 K. C)The reaction has an extremely small equilibrium constant, thus almost no product will form. D) The reverse reaction has a lower activation energy than the forward reaction, so the forward reaction does not occur. =-97

B) A high activation energy makes the forward reaction extremely slow at 298 K.

Which of the following molecules contains only single bonds? A) CH3COOH B) CH3CH2COOCH3 C) C2H6 D) C6H6 E) HCN

B) CH3CH2COOCH3

Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits each statement. A choice may be used once, more than once, or not at all in each set. Refer to the following compounds. (A) CH3CH2CH2CH3 (B) CH3CH2CH2OH (C) CH3COCH3 (D) CH3COOH (E) CH3CH2CH2NH2 Is isomeric with CH3CH2CHO

C) CH3COCH3

C2H6(g)+72O2(g)→2CO2(g)+3H2O(l)ΔH°=−1560kJC(graphite)+O2(g)→CO2(g)ΔH°=−394kJ Given the equations and the values of ΔH° for the combustion of C2H6(g) and the combustion of C(graphite) represented above, which of the following additional information is needed to determine the values of ΔH° for the overall reaction 2C(graphite)+3H2(g)→C2H6(g) ? A) C(diamond)→C(graphite) ΔH°=−2kJ C(diamond)→C(graphite) ΔH°=−2kJ B) C2H4(g)+H2(g)→C2H6(g) ΔH°=−134kJ C2H4(g)+H2(g)→C2H6(g) ΔH°=−134kJ C) H2(g)+12O2(g)→H2O(l) ΔH°=−286kJ H2(g)+12O2(g)→H2O(l)⁢ ΔH°=−286kJ D) H2O(l)→H2O(g) ΔH°=+41kJ

C) H2(g)+12O2(g)→H2O(l) ΔH°=−286kJ H2(g)+12O2(g)→H2O(l)⁢ ΔH°=−286kJ

CH3I+NaOH→CH3OH+NaI The rate of the reaction represented by the chemical equation shown above is expressed as rate=k[CH3I][NaOH]. Based on this information, which of the following claims is correct? A) The reaction will proceed at a slower rate with increasing temperature. B) The rate of the reaction will double when the concentrations of both CH3Iand NaOH are doubled. C) The rate of the reaction will double if the concentration of CH3I is doubled while keeping the concentration of NaOH constant. D) A larger amount of CH3OH will be produced if the concentrations of CH3II and NaOH are halved.

C) The rate of the reaction will double if the concentration of CH3I is doubled while keeping the concentration of NaOH constant.

2Fe2O3(s)+3C(s)→4Fe(s)+3CO2(g)2Fe2O3(s)+3C(s)→4Fe(s)+3CO2(g) In a blast furnace, the reaction represented above occurs, producing Fe(s) from its ore, Fe2O3(s). The reaction is thermodynamically favorable and based on coupling the two reactions represented below. 2Fe2O3→4Fe+3O2 C+O2→CO2 Which of the following identifies a limitation in how the representations above describe a system of coupled reactions? A) None of the equations are balanced. B) The values of ΔS° for each reaction are not shown. C) The values of ΔG° for each reaction are not shown. D)The coupled reactions lack a common intermediate species.

C) The values of ΔG° for each reaction are not shown.

A 2.0 mol sample of CO(g) and a 2.0 mol sample of H2O(g) are introduced into a previously evacuated 100. L rigid container, and the temperature is held constant as the reaction represented above reaches equilibrium. Which of the following is true at equilibrium? A) [H2O] > [CO] and [CO2] > [H2] B) [H2O] > [H2] C) [CO2] > [CO] D) [CO] = [H2O] = [CO2] = [H2]

C) [CO2] > [CO]

3 O2(g) ⇄ 2O3(g) Kc = 1.8 × 10−56 at 570 K For the system represented above, [O2] and [O3] initially are 0.150 mol/L and 2.5 mol/L respectively. Which of the following best predicts what will occur as the system approaches equilibrium at 570 K? A) The amount of O3(g) will increase, because Q < Kc. B) The amount of O3(g) will decrease, because Q < Kc. C) The amount of O3(g) will increase, because Q > Kc. D) The amount of O3(g) will decrease, because Q > Kc.

D) The amount of O3(g) will decrease, because Q > Kc.

A mixture of NO2(g) and N2O4(g) is placed in a glass tube and allowed to reach equilibrium at 70°C, as represented above. If is 1.33 atm when the system is at equilibrium at 70°C, what is ? A) 0.44 atm B) 2.0 atm C) 2.3 atm D) 4.0 atm

4.0 atm

Which of the following numerical expressions gives the number of moles in 5.0g of CaO? A) 5.0 x 56g/mol B) 5.0 g/56g/mol C)56 g/mol/5.0 g D) 1/5.0g x 1/56 g/mol

5.0 g/56g/mol

Which of the following is the correct mathematical expression to use to calculate the pH of a 0.10M aqueous Ba(OH)2 solution at 25°C? A) pH=−log(0.10) B) pH=−log(0.20) C) pH=14.00−log(0.10) D) pH=14.00+log(0.20)

D) pH=14.00+log(0.20)

Which of the following species is NOT planar? A) CO32- B) NO3- C) ClF3 D) BF3 E) PCl3

E) PCl3

COCl2(g) ⇄ CO(g) + Cl2(g) COCl2(g) decomposes according to the equation above. When pure COCl2(g) is injected into a rigid, previously evacuated flask at 690 K, the pressure in the flask is initially 1.0 atm. After the reaction reaches equilibrium at 690 K, the total pressure in the flask is 1.2 atm. What is the value of Kp for the reaction at 690 K? A) 0.040 B) 0.050 C)0.80 D) 1.0

B) 0.050

Which of the following is the correct electron configuration for a ground-state atom of magnesium (atomic number 12) ? A) 1s2 2s2 2p8 B) 1s2 2s2 3s2 3p6 C) 1s2 2s2 2p6 3s2 D ) 1s2 2s2 3s4 3p4

C) 1s2 2s2 2p6 3s2

What volume of a 0.100MHCl stock solution should be used to prepare 250.00mL of 0.0250MHCl? A) 1.00mL B) 16.0mL C) 62.5mL D) 100.mL

C) 62.5mL

Of the following single bonds, which is the LEAST polar? A) N—H B) H—F C) O—F D) I—F

C) O—F

Bi 83214→Po 84214+e−1 0 Bismuth-214 undergoes first-order radioactive decay to polonium-214 by the release of a beta particle, as represented by the nuclear equation above. Which of the following quantities plotted versus time will produce a straight line? A) [Bi] B) [Po] C) ln[Bi] D) 1/[Bi]

C) ln[Bi]

A 500.mL aqueous solution of Na3PO4 (molarmass=164g/mol) was prepared using 82gof the solute. What is the molarity of Na3PO4 in the resulting solution? A) 0.0010M B) 0.16M C) 0.25M D) 1.0M

1.0 M

2Mg(s)+SiCl4(l)→2MgCl2(s)+Si(s) Which of the following statements about the reaction represented above is correct? A) It is an oxidation-reduction reaction, and Mg is oxidized. B) It is an oxidation-reduction reaction, and electrons are transferred from SiCl4 to Mg C) It is an oxidation-reduction reaction, and the oxidation number of Cl changes from +4 to +2 D) It is not an oxidation-reduction reaction because none of the oxidation numbers change.

A) It is an oxidation-reduction reaction, and Mg is oxidized.

HC2H3O2(aq)+OH−(aq)→C2H3O2−(aq)+H2O(l) A student carried out a titration using HC2H3O2(aq) and NaOH(aq). The net ionic equation for the neutralization reaction that occurs during the titration is represented above. The NaOH(aq) was added from a buret to the HC2H3O2(aq) in a flask. The equivalence point was reached when a total of 20.0mL of NaOH(aq) had been added to the flask. How does the amount of HC2H3O2(aq) in the flask after the addition of 5.0mL of NaOH(aq) compare to the amount of HC2H3O2(aq) in the flask after the addition of 1.0mL of NaOH(aq), and what is the reason for this result? A) It is less because more HC2H3O2(aq)HC2H3O2(aq) reacted with the base. B) It is the same because the half-equivalence point has not been reached. C) It is the same because all of the coefficients in the neutralization equation are 1. D) It is greater because HC2H3O2(aq)HC2H3O2(aq) is a proton donor.

A) It is less because more HC2H3O2(aq)HC2H3O2(aq) reacted with the base.

HC2H3O2(aq)+H2O(l)⇄H3O+(aq)+C2H3O2−(aq) pKa=4.76 The equilibrium for the acid ionization of HC2H3O2 is represented by the equation above. A student wants to prepare a buffer with a pH of 4.76 by combining 25.00mL of 0.30MHC2H3O2 with 75.00mL of 0.10MNaC2H3O2. While preparing the buffer, the student incorrectly measures the volume of NaC2H3O2 so that the actual volume used is 76.00mL instead of 75.00mL. Based on the error, which of the following is true about the buffer prepared by the student? A) The pH of the buffer will be slightly lower than 4.76 because the total volume of the buffer is 101.00mL instead of 100.00mL, and the HC2H3O2 was diluted. B) The pH of the buffer will be slightly lower than 4.764.76 because the amount of C2H3O2− added was higher than the amount of HC2H3O2 added. C) The buffer solution will have a slightly higher capacity for the addition of bases than for the addition of acids because the total volume of the buffer is 101.00mL instead of 100.00mL, and the HC2H3O2 was diluted. D) The buffer solution will have a slightly higher capacity for the addition of acids than for the addition of bases because the amount of C2H3O2−C added was higher than the amount of HC2H3O2 added.

A) The pH of the buffer will be slightly lower than 4.76 because the total volume of the buffer is 101.00mL instead of 100.00mL, and the HC2H3O2 was diluted.

A student was given two clear liquids; a colorless liquid and a dark-blue liquid. The student was asked to combine the liquids in a beaker and record observations. Which of the following results, if true, would provide the best evidence that a chemical change took place when the liquids were combined? A) The resulting mixture was cloudy. B) The total volume of the mixture was equal to the sum of the initial volumes. C) The resulting liquid was light blue. D) The liquids formed two separate layers in the beaker.

A) The resulting mixture was cloudy.

When a magnesium wire is dipped into a solution of lead (II) nitrate, a black deposit forms on the wire. Which of the following can be concluded from this observation? A) The standard reduction potential, E°, for Pb2+(aq) is greater than that for Mg2+(aq). B) Mg(s) is less easily oxidized than Pb(s). C) An external source of potential must have been supplied. D) The magnesium wire will be the cathode of a Mg/Pb cell. E) Pb(s) can spontaneously displace Mg2+(aq) from solution.

A) The standard reduction potential, E°, for Pb2+(aq) is greater than that for Mg2+(aq).

In pure water, some of the molecules ionize according to the equation H2O→H++OH−. The extent of the ionization increases with temperature. A student heats pure water and records the measured pH at 50°C as 6.6. Based on this information, which of the following mathematical relationships gives the pOH of pure water at 50°C? A) pOH=pH B) pOH=1/pH C) pOH=14−pH D) pOH=1×10−14/pH

A) pOH=pH

A gaseous air‑fuel mixture in a sealed car engine cylinder has an initial volume of 600.mL at 1.0atm. To prepare for ignition of the fuel, a piston moves within the cylinder, reducing the volume of the air‑fuel mixture to 50.mL at constant temperature. Assuming ideal behavior, what is the new pressure of the air‑fuel mixture? A) About 0.083atm0.083atm, because the initial volume of the gas mixture was 12 times larger than its final volume. B) About 12atm12atm, because the volume of the gas mixture decreased by a factor of 12. C) About 120.atm120.atm, because the initial volume of the gas mixture was 120 times larger than its final volume. D) About 550.atm550.atm, because the change in the volume of the gas mixture was 550.mL550.mL.

B) About 12atm12atm, because the volume of the gas mixture decreased by a factor of 12.

Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits the statement. A choice may be used once, more than once, or not at all. The question refers to the following species. (A) H2O (B) NH3 (C) BH3 (D) CH4 (E) SiH4 Has a central atom with less than an octet of electrons

B) BH3

A student carefully drops a 9.0g solid Zn pellet initially at 50.0°C into an insulated cup containing 30.0g of water at 27.8°C. The student predicts that the temperature of the water will increase after the pellet is added. Which of the following statements is the best justification for the student's prediction? A) The metallic bonds between Zn atoms will break when the Zn is exposed to the water molecules, releasing energy that will be absorbed by the water molecules. B) Collisions between the water molecules and the surface of the Zn pellet will result in the transfer of energy, increasing the average kinetic energy of the water molecules. C) The strength of the hydrogen bonds between the water molecules will increase when the Zn pellet is added, decreasing the average kinetic energy of the water molecules. D) Collisions between Zn atoms in the solid will increase in frequency when the Zn is exposed to the water molecules, resulting in the transfer of energy to the surroundings.

B) Collisions between the water molecules and the surface of the Zn pellet will result in the transfer of energy, increasing the average kinetic energy of the water molecules.

Ba2+(aq)+SO42−(aq)→BaSO4(s) A student obtains a 10.0g sample of a white powder labeled as BaCl2. After completely dissolving the powder in 50.0mL of distilled water, the student adds excess Na2SO4(s), which causes a precipitate of BaSO4(s) to form, as represented by the equation above. The student filters the BaSO4(s), rinses it, and dries it until its mass is constant. Which of the following scientific questions could best be answered based on the results of the experiment? A) Is the Na2SO4(s) used in the experiment pure? B) Is the BaCl2(s)BaCl2(s) used in the experiment pure? C) What is the molar solubility of BaCl2BaCl2 in water? D)What is the molar solubility of BaSO4BaSO4 in water?

B) Is the BaCl2(s) used in the experiment pure?

Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits the statement. A choice may be used once, more than once, or not at all. The question refers to the following species. (A) H2O (B) NH3 (C) BH3 (D) CH4 (E) SiH4 Has a trigonal-pyramidal molecular geometry

B) NH3

Two aqueous NaCl solutions of equal volume and concentration were kept in flasks and held at different temperatures. The two solutions were combined in a larger flask. Based on this information, which of the following predictions is correct? A) The average kinetic energy of the particles in the cooler solution will decrease as they collide with the particles from the warmer solution. B) The average kinetic energy of the particles in the cooler solution will increase as they collide with the particles from the warmer solution. C) The particles from the cooler solution and the particles from the warmer solution will reach thermal equilibrium through collisions, at which time the average kinetic energy of the particles in the mixture will be lower than the average kinetic energy that the particles had in the cooler solution. D) The particles from the cooler solution and the particles from the warmer solution will reach thermal equilibrium through collisions, at which time the average kinetic energy of the particles in the mixture will be higher than the average kinetic energy that the particles had in the warmer solution.

B) The average kinetic energy of the particles in the cooler solution will increase as they collide with the particles from the warmer solution.

A student obtains a mixture of the chlorides of two unknown metals, X and Z. The percent by mass of X and the percent by mass of Z in the mixture is known. Which of the following additional information is most helpful in calculating the mole percent of XCl(s) and of ZCl(s) in the mixture? A) The number of isotopes of Cl B) The molar masses of X and Z C) The density of either XCl(s) or ZCl(s) D) The percent by mass of Cl in the mixture

B) The molar masses of XX and Z

A student measures the mass of a sample of a metallic element, M. Then the student heats the sample in air, where it completely reacts to form the compound MO. The student measures the mass of the compound that was formed. Which of the following questions can be answered from the results of the experiment? A) What is the density of M? B) What is the molar mass of M? C) What is the melting point of M? D) What is the melting point of MO?

C What is the molar mass of M?

Na2S2O3(aq)+4NaOCl(aq)+2NaOH(aq)→2Na2SO4(aq)+4NaCl(aq)+H2O(l) The enthalpy change for the reaction represented by the chemical equation shown above is ΔH°=−1236kJ/molrxn. When 2.00mol of NaOCl(aq) reacts completely with an excess of Na2S2O3(aq) and of NaOH(aq), which of the following enthalpy changes occurs? A) 618kJ of heat is absorbed. B) 2470kJ of heat is absorbed. C) 618kJ of heat is released. D) 2470kJ of heat is released.

C) 618kJ of heat is released.

C12H22O11(aq)+H2O(l)→2C6H12O6(aq) The chemical equation shown above represents the hydrolysis of sucrose. Under certain conditions, the rate is directly proportional to the concentration of sucrose. Which statement supports how a change in conditions can increase the rate of this reaction? A) Increasing the amount of water in which the sugar is dissolved will increase the frequency of collisions between the sucrose molecules and the water molecules resulting in an increase in the rate of hydrolysis. B) Decreasing the temperature will increase the frequency of the collisions between the sucrose molecules and the water molecules resulting in an increase in the rate of hydrolysis. C) Increasing the concentration of sucrose will increase the rate of hydrolysis by increasing the frequency of the collisions between the sucrose and the water molecules. D) Decreasing the concentration of sucrose will increase the rate of hydrolysis by increasing the frequency of the collisions between the sucrose and the water molecules.

C) Increasing the concentration of sucrose will increase the rate of hydrolysis by increasing the frequency of the collisions between the sucrose and the water molecules.

HCl(aq)+NH3(aq)→NH4+(aq)+Cl−(aq) The chemical reaction between HCl(aq) and NH3(aq) is represented above. A student combines equimolar amounts of HCl(aq) and NH3(aq), both solutions initially at 24°C, in a coffee-cup calorimeter. The student observes that the mixture reaches a temperature of 28°C. Based on the experimental results, which of the following can be concluded about the reaction? A) It is an endothermic process, because energy is released by the reaction and is gained by the reaction mixture. B) It is an endothermic process, because energy is absorbed by the reaction and is lost from the reaction mixture. C) It is an exothermic process, because energy is released by the reaction and is gained by the reaction mixture. D) It is an exothermic process, because energy is absorbed by the reaction and is lost from the reaction mixture.

C) It is an exothermic process, because energy is released by the reaction and is gained by the reaction mixture.

A chemistry teacher carried out several demonstrations, and students recorded their observations. For one of the demonstrations, a student concluded that a physical change took place, but not a chemical change. Which of the following observations could the student have made of the results of the demonstration? A) Two colorless solutions were combined, and the resulting solution was pink. B) When a solid was added to a liquid, sparks were produced. C) One piece of solid substance was changed into small pieces. D) When two solutions were combined, a precipitate formed.

C) One piece of solid substance was changed into small pieces.

HF(aq)+H2O(l)⇄H3O+(aq)+F−(aq) The equation above represents the acid ionization equilibrium for HF. To prepare a buffer with pH≈3.50, 4.20g of NaF(s) should be added to 500.0mL of 0.100MHF(aq). The buffer is accidentally prepared using 90% pure NaF(s) instead of 99% pure NaF(s). Assume that the impurities in the NaF(s) samples are inert. Which of the following explains how the error affects the pH and capacity of the buffer? A) The pH is slightly higher than 3.50 and it has a lower capacity for the addition of acids because less than 4.20g of NaF(s) was added. B) The pH is slightly higher than 3.50 and it has a higher capacity for the addition of acids because more than 4.20gof NaF(s) was added. C) The pH is slightly lower than 3.50 and it has a lower capacity for the addition of acids because less than 4.20g of NaF(s) was added. D) The pH is slightly lower than 3.50 and it has a higher capacity for the addition of acids because more than 4.20g of NaF(s) was added.

C) The pH is slightly lower than 3.50 and it has a lower capacity for the addition of acids because less than 4.20g of NaF(s) was added.

Which of the following pairs of mathematical expressions can be used to correctly calculate the pH and pOH of a 0.0015MKOH(aq) solution at 25°C? A) pH=−log(14.00−0.0015) and pOH=−log(0.0015) B) pH=log(0.0015)−14.00 and pOH=−log(0.0015) C) pH=14.00−(−log⁡(0.0015)) and pOH=−log(0.0015) D) pH=−(−log⁡(0.0015)) and pOH=14.00−(−log(0.0015))

C) pH=14.00−(−log⁡(0.0015)) and pOH=−log(0.0015)

HA(aq)+H2O(l)⇄A−(aq)+H3O+(aq)HA(aq)+H2O(l)⇄A−(aq)+H3O+(aq)ΔG°=+35kJ/molrxnΔG°=+35kJ/molrxn Based on the chemical equation and ΔG° given above, which of the following justifies the claim that HA(aq) is a weak acid? A) Because ΔG°>>0, Ka>>1 , and HA completely dissociates. B) Because ΔG°>>0, Ka>>1, and HA almost completely dissociates. C)Because ΔG°>>0, Ka<<1, and HA only partially dissociates. D) Because ΔG°>>0, Ka<<1, and HA does not dissociate.

C)Because ΔG°>>0, Ka<<1, and HA only partially dissociates.

How many grams of NaCl (molarmass=58g/mol) are needed to prepare 100.mL of a 0.25M NaCl solution? A) 0.23g B) 0.43g C) 0.67g D) 1.5g

D) 1.5g

The gases CO2(g) and NH3(g) can be liquefied at 20°C by compressing them to sufficiently high pressures. A student claims that NH3(g) can be liquefied at a lower pressure than CO2(g) can be liquefied. Which of the following is the best justification for this claim? A) At 20°C20°C, the average speed of NH3NH3 molecules is greater than that of CO2CO2 molecules because NH3NH3 molecules have less mass than CO2CO2 molecules have. B) CO2CO2 is a nonpolar molecule that has no significant intermolecular forces, whereas NH3NH3 has strong London dispersion intermolecular forces. C) Both CO2CO2 and NH3NH3 are nonpolar molecules that have only London dispersion intermolecular forces, but the larger electron cloud of CO2CO2 molecules causes it to have stronger intermolecular forces. D) CO2CO2 is a nonpolar molecule that has London dispersion intermolecular forces that are weaker than the dipole-dipole and London dispersion forces between the polar NH3NH3 molecules.

D) CO2CO2 is a nonpolar molecule that has London dispersion intermolecular forces that are weaker than the dipole-dipole and London dispersion forces between the polar NH3NH3 molecules.

A beaker was half filled with freshly distilled H2O and placed on a hot plate. As the temperature of the water reached 100°C, vigorous bubbling was observed in the beaker. The gaseous contents of the bubbles were analyzed. The presence of which of the following substances would support the claim that the observed phenomenon was a physical change? A) H2(g) B) O2(g) C) CO2(g) D) H2O(g)

D) H2O(g)

2 NO(g) + O2(g) → 2 NO2(g) Consider the following mechanism for the reaction represented above. Step 1: 2 NO ⇄ N2O2 (fast reversible) Step 2: N2O2 + O2 → 2 NO2 (slow) Which of the following statements is true? A) Step 1 represents a unimolecular reaction. B) Increasing the concentration of NO will decrease the overall rate of the reaction. C) Raising the temperature will have no effect on the numerical value of the rate constant. D) The rate law that is consistent with the mechanism is rate = k[NO]2[O2].

D) The rate law that is consistent with the mechanism is rate = k[NO]2[O2].

To prepare a buffer solution for an experiment, a student measured out 53.49g of NH4Cl(s) (molar mass 53.49g/mol) and added it to 1.0L of 1.0MNH3(aq). However, in the process of adding the NH4Cl(s) to the NH3(aq), the student spilled some of the NH4Cl(s) onto the bench top. As a result, only about 50.g of NH4Cl(s) was actually added to the 1.0MNH3(aq). Which of the following best describes how the buffer capacity of the solution is affected as a result of the spill? A) The solution has a greater buffer capacity for the addition of base than for acid, because [NH3]<[NH4+] B) The solution has a greater buffer capacity for the addition of base than for acid, because [NH3]>[NH4+] C) The solution has a greater buffer capacity for the addition of acid than for base, because [NH3]<[NH4+] D) The solution has a greater buffer capacity for the addition of acid than for base, because [NH3]>[NH4+]

D) The solution has a greater buffer capacity for the addition of acid than for base, because [NH3]>[NH4+]

Zn(s)+2 HCl(aq)→ZnCl2(aq)+H2(g) Zn(s) reacts with HCl(aq) according to the equation shown above. In trial 1 of a kinetics experiment, a 5.0g piece of Zn(s) is added to 100mL of 0.10MHCl(aq). The rate of reaction between Zn(s) and HCl(aq) is determined by measuring the volume of H2(g) produced over time. In trial 2 of the experiment, 5.0g of powdered Zn(s) is added to 100mL of 0.10MHCl(aq). Which trial will have a faster initial rate of reaction and why? A) Trial 1, because there is a higher concentration of Zn(s) in the reaction mixture. B) Trial 1, because the sample of Zn(s) has less surface area for the reaction to take place. C) Trial 2, because there is a higher concentration of HCl(aq) in the reaction mixture. D) Trial 2, because the sample of Zn(s) has a greater surface area for the reaction to take place

D) Trial 2, because the sample of Zn(s) has a greater surface area for the reaction to take place

Zn(s)+2 HCl(aq)→ZnCl2(aq)+H2(g) Zn(s) reacts with HCl(aq) according to the equation shown above. In trial 1 of a kinetics experiment, a 5.0g piece of Zn(s) is added to 100mL of 0.10MHCl(aq). The rate of reaction between Zn(s) and HCl(aq) is determined by measuring the volume of H2(g) produced over time. In trial 2 of the experiment, 5.0g of powdered Zn(s) is added to 100mL of 0.10MHCl(aq). Which trial will have a faster initial rate of reaction and why? A) Trial 1, because there is a higher concentration of Zn(s) in the reaction mixture. B) Trial 1, because the sample of Zn(s) has less surface area for the reaction to take place. C) Trial 2, because there is a higher concentration of HCl(aq) in the reaction mixture. D) Trial 2, because the sample of Zn(s) has a greater surface area for the reaction to take place.

D) Trial 2, because the sample of Zn(s) has a greater surface area for the reaction to take place.

CH4(g)+2O2(g)⇄CO2(g)+2H2O(g)ΔH°rxn=−803kJ/molrxn ΔS°rxn=−5J/(molrxn⋅K) The chemical equation above represents the exothermic reaction of CH4(g) with O2(g). Which of the following best helps to explain why the reaction is thermodynamically favored (ΔG<0) at 2000K and 1atm? A)The total number of gaseous product molecules is less than the total number of gaseous reactant molecules, thus ΔS<0. B) The total number of gaseous product molecules is greater than the total number of gaseous reactant molecules, thus ΔS>0. C) The amount of energy released when the product bonds form is much less than the amount of energy needed to break the reactant bonds. D)The amount of energy released when the product bonds form is much greater than the amount of energy needed to break the reactant bonds.

D)The amount of energy released when the product bonds form is much greater than the amount of energy needed to break the reactant bonds.

Which of the following statements is true for the equilibrium vapor pressure of a liquid in a closed system? A) It remains constant when the temperature increases. B) It decreases to half its original value if the volume of the gas phase is doubled. C) It increases to twice its original value if the volume of the liquid phase is doubled. D) It decreases to half its original value if the surface area of the liquid is reduced by one-half. E) It is independent of the volume of the vapor phase.

E) It is independent of the volume of the vapor phase.

Which of the following processes involves the greatest increase in entropy? A) SO3(g) + H2(g) → SO2(g) + H2O(g) B) N2(g) + 3 H2(g) → 2 NH3(g) C) Ag+(aq) + Cl-(aq) → AgCl(s) D) C2H2(g) + 2 H2(g) → C2H6(g) E) MgSO3(s) → MgO(s) + SO2(g)

E) MgSO3(s) → MgO(s) + SO2(g)