chemistry exam 3
If the rate of formation of ammonia is 0.345 M/s, what is the rate of disappearance of N2? N2(g)+3H2(g)→2NH3(g) a.0.173 M/s d.245 M/s b.0.345 M/s e.0.518 M/s c.0.690 M/s
A. 0.173 M/S
If the rate of formation of dinitrogen is 0.540 M/s, what is the rate of disappearance of oxygen? 4NH3(g)+3O2(g)→2N2(g)+6H2O(g) a.0.810 M/s d.0.360 M/s b.1.08 M/s e.0.540 M/s c.1.62 M/s
A. 0.810 M/S
The rate law of a particular reaction was determined to be Rate =k. What is the unit of the rate constant for the reaction? a.M/s d.1/s b.1/(Ms) e.Ms c.1/(Ms2)
A. M/s
For the reaction 2A +3B →4C +5D, the rate of the reaction in terms of ΔA would be written as ________ a.−ΔA/Δt. d.12ΔA/Δt. b.-12ΔA/Δt. e.−2ΔA/Δt. c.+ΔA/Δt.
B -1/2 A/tD
The greatest NO concentration is observed: a) in the morning before rush hour b) in the morning after rush hour c) in midmorning d) noon e) midafternoon
B) in the morning after rush hour
A proposed mechanism for the reduction of nitrogen as NO by hydrogen is: Step 1: H2(g)+2NO(g)→N2O(g)+H2O(g) Step 2: N2O(g)+H2(g)→N2(g)+H2O(g)What is the molecularity of step 1? a.unimolecular b.bimolecular c.termolecular d.zero molecular (spontaneous) e.More information is needed to answer this question.
C) termolecular
HI dissociates to form I2and H2: 2HI(g)→H2(g)+I2(g) If the concentration of HI changes at a rate of −0.45 M/s, what is the rate of appearance of I2(g)? a.0.90 M/s d.1.00 M/s b.0.45 M/s e.0.13 M/s c.0.23 M/s
C. 0.23 M/s
Using the reaction shown below, which statement is correct? H2(g)+2ICl(g)→I2(g)+2HCl(g) a.The concentration of all compounds are changing by the same amount at all times. b.The HCl concentration increases at the same rate as the concentration of iodine. c.The concentration of hydrogen decreases at the same rate as the concentration of ICl. d.The concentration of HCl increases twice as fast as the concentration of iodine. e.None of these statements is correct.
D. the concentration of HCL increases twice as fast as the concentration of iodine
The device in automobiles that has decreased NO and partially oxidized hydrocarbons from exhaust gases is termed:
E. Catalytic Converter
If the rate of formation of ammonia is 0.345 M/s, what is the rate of disappearance of N2? 12N2(g)+32H2(g)→NH3(g) a.0.173 M/s d.245 M/s b.0.345 M/s e.0.518 M/s c.0.690 M/s
a. 0.173 M/S
Indicate which of the following compounds is not a component of photochemical smog: a: O3 b: H20 c: NO2 d: NO e: organic molecules
b H20
At 0 K, the entropy of a perfect crystal is ________ a.>0. b.=0. c.<0. d.>0, =0, or <0, depending on the chemical structure of the crystal. e.>0 or =0, depending on the chemical structure of the crystal.
b) = 0
The first-order reaction A →B, has k=5.67 s−1. If [A]0=0.500 M, how long will it take to reach [A] =0.124 M? a.0.122 s d.0.246 s b.0.100 s e.0.488 s c.8.18 s
d) 0.246 s
Which of these could be the units of the rate constant for a first-order reaction? a.M/s d.1/s b.1/Ms e.Ms c.1/Ms
d. 1/s
Consider the rate law expression Rate =k[A][B]2. Which of the following is nottrue about the reaction? a.The reaction is second order in B. b.The reaction is first order in A. c.The reaction is overall third order. d.Doubling the concentration of B will double the rate. e.All statements (A-D) are true.
d. doubling the concentration of B will double the rate
Indicate which one of the following reactions most certainly does not result in a decrease in entropy. a.O2(g)O2(l) b.Ca2+(aq)+2Cl−(aq))CaCl2(s) c.MgSO4(s)+7H2O(g)MgSO4⋅7H2O(s) d.Na(l)+12Cl2(g)→NaCl(s) e.2NH3(g)N2(g)+3H2(g)
e.2NH3(g)N2(g)+3H2(g)
Suppose ΔG°is -2.0 kJ/mol for a hypothetical reaction in which A converts into B. Which of the following statements describes an equilibrium mixture of A and B? a.Only A is present. b.Only B is present. c.A and B have equal concentrations. d.A has a higher concentration than B. e.B has a higher concentration than A.
e.B has a higher concentration than A.
Which of the relationships between the free-energy change of a system and associated entropy changes is true?a.ΔGsys=+TΔSsystem d.ΔGsys=−TΔSsurroundings b.ΔGsys=−TΔSsystem e.ΔGsys=−TΔSuniverse c.ΔGsys=+TΔSuniverse
e.ΔGsys=−TΔSuniverse
The mechanism for the reaction 2H2O2(aq)→2H2O(l)+O2(g)in the presence of I−(aq) is proposed to be: Step 1: H2O2(aq)+I−(aq)→H2O(l)+OI−(aq) Step 2: H2O2(aq)+OI−(aq)→H2O(l)+O2(g)+I−(aq) Which of the following species is a catalyst? a.I− d.OI− b.H2O2 e.This mechanism has no catalysts. c.H2O
A) I-
A second-order reaction (2A →B) with a rate constant of 0.350 M−1s −1is found to have a half-life of 3.45 s. What was the initial concentration of the reactant, [A]0? a.0.828 M d.1.21 M b.0.201 M e.0.350 M c.1.00 M
A. 0.828 M
In the combustion of methane, CH4(g)+2O2(g)→CO2(g)+2H2O(g), which reactant has the greatest rate of disappearance? a.CH4 b.O2 c.CO2 d.H2O e.CH4 and O2 have the same rate of disappearance.
B. O2
One reaction that occurs in an automobile catalytic converter is the conversion of nitrogen monoxide to nitrogen and oxygen. How is the rate of this reaction related to the rate at which the concentration of a reactant or product changes? 2NO(g) →N2(g) +O2(g) I. Rate =Δ[NO]/Δt II. Rate =−Δ[NO]/Δt III. Rate =Δ[N2]/Δt IV. Rate =Δ[O2]//Δt a.I only d.I, III, and IV only b.II only e.II, III, and IV only c.III and IV only
C III and IV only
One reaction that occurs in an automobile catalytic converter is the conversion of carbon monoxide to carbon dioxide. How is the rate of this reaction related to the rate at which the concentration of a reactant or product changes? 2CO(g) +O2(g) →2CO2(g) I. Rate =Δ[CO]/Δt II. Rate =−Δ[CO]/Δt III. Rate =−Δ[O2]/Δt IV. Rate =Δ[CO2]/Δt a.I only d.II and III only b.II only e.II, III, and IV only c.III only
C III only
What is the entropy change to the surroundings when 1 mol of ice melts in someone's hand if the hand temperature is 32°C? Assume a final temperature for the water of 0°C. The heat of fusion of ice is 6.01 kJ/mol. a.−188 J/K d.+19.7 J/K b.−22.0 J/K e.+188 J/K c.−19.7 J/K
C)−19.7 J/K
For the reaction 2A →4B +3D, the rate of the reaction in terms of ΔB would be written as ________ a.−ΔB/Δt. d.+14ΔB/Δt. b.+ΔB/Δt. e.+4ΔB/Δt. c.−14ΔB/Δt.
D +1/4 B/ t
The difference between an average rate and an instantaneous rate is ________ a.the average rate is taken over a longer time period. b.the instantaneous rate is taken from the slope of the curve at a specific time. c.They are not different if the time interval chosen is small enough. d.All of the above are correct.
D all of the above are correct
A reaction with a low enthalpy of reaction value is notspontaneous at low temperature but becomes spontaneous at high temperature. What are the signs for ΔH°and ΔS°, respectively? a.+, − b.−, − c.−, + d.+, + e.Insufficient data is provided to answer this question.
D) +, +
A reaction with a low enthalpy of reaction value is spontaneous at high temperature but becomes notspontaneous at low temperature. What are the signs for ΔH°and ΔS°, respectively? a.+, − b.−, − c.−, + d.+, + e.Insufficient data is provided to answer this question.
D) +, +
Which of the following processes is/are spontaneous? I. Iron in the open air rusts. II. Liquid water in a freezer turns to ice. III. A spark ignites a mixture of propane and air. a.I only d.II and III only b.I and II only e.I, II, and III are all spontaneous. c.I and III only
E) I, II, and III are all spontaneous
The rate of popcorn popping at different temperatures was found to be described by the Arrhenius equation. How many times faster does the popcorn pop at 210°C compared with that at 180°C when the activation energy is 167 kJ/mol? a.15.7 d.1.20 b.8.80 ×106 e.42.6 c.8.38 ×106
a) 15.7
Given the following two measurements of the equilibrium constant for a reaction, calculate ΔH°for the reaction. T,°C K15 2.6 ×10325 9.3 ×104 a.255 kJ/mol d.−3,250 kJ/mol b.−271 kJ/mol e.+271 kJ/mol c.3,250 kJ/mol
a) 255 kJ/mol
Perfect crystals of carbon monoxide (CO) are difficult to prepare because the very small dipole moment allows a few molecules to align in a pattern such as CO OC CO instead of CO CO CO. If such disordered crystals were cooled to 0 K, what would be the value of their absolute entropy? a.>0 b.=0 c.<0 d.>0, =0, or <0, depending on how carefully it was cooled e.>0 or =0, depending on how carefully it was cooled
a) > 0
Indicate which one of the following reactions most certainly results in a negative ΔSsys. a.H2O(g)H2O(s) b.CaCO3(s)CaO(s)+CO2(g) c.CuSO4⋅5H2O(s)CuSO4(s)+5H2O(g) d.14O2(g)+3NH4NO3(s)+C10H22(l)→3N2(g)+17H2O(g)+10CO2(g) e.CO2(aq)CO2(g)
a) H2O(g)H2O(s)
In a biochemical reaction, A +B →C with ΔGrxn°=30 kJ/mol. Which of the following reactions might be effectively coupled to this reaction so that it becomes more spontaneous? I.C +D →B +E ΔGrxn°=−40 kJ/mol II.C +D →B +E ΔGrxn°=+40 kJ/mol a.I only b.II only c.I or II d.Neither I nor II can increase spontaneity. e.No coupling is required, because the reaction is already spontaneous.
a) I only
Which of the following will have the greatest standard molar entropy (S°)? a.NH3(g) d.H2O(l) b.He(g) e.CaCO3(s) c.C(s, graphite)
a) NH3(G)
Boltzmann derived the relationship S=k ln W, where Wis the ________ a.number of microstates. d.Wentworth factor. b.vibrational energy. e.potential energy. c.kinetic energy.
a) number of microstates
What types of motion does a molecule of chlorine have?a.translational, rotational, and vibrational b.kinetic energy and potential energy c.microstate and macrostate d.Boltzmann and non-Boltzmann e.all of the above
a) translational, rotational, vibrational
If the rate of appearance of O2 in the reaction: 2O3 (g) → 3O2 (g) is 0.250 M/s over the first 5.50 s, how much oxygen will form during this time? a.1.38 M d.0.25 M b.4.13 M e.0.46 M c.0.69 M
a. 1.38 M
The half-life (t1/2) of a first-order reaction is 0.100 s. What is the rate constant? a.6.93 s−1 d.0.144 s−1 b.0.693 s−1 e.3.01 s−1 c.0.0693 s−1
a. 6.93 s-1
The standard molar entropy of magnesium fluoride (MgF2) is 57.2 J/(mol ⋅K). What is the entropy of 4.75 g of MgF2? a.+4.36 J/K d.−272 J/K b.−4.36 J/K e.0 J/K c.+272 J/K
a.+4.36 J/K
Which of the following must be true for the microstates of a system? I.The energy of each microstate equals the energy of the system. II.The entropy of each microstate equals the entropy of the system. III.The number of microstates equals the entropy of the system. a.I only d.I and III only b.II only e.I, II, and III are all true. c.III only
a.I only
Which statement is true of the ideal gas constant, R, and the Boltzmann constant, kB? a.R/kB =Avogadro's number. b.They both have units of J ⋅mol−1⋅K−1. c.kBR=Avogadro's number. d.kB/R=Avogadro's number. e.8.3145 J is not equivalent to 0.082058 L ⋅atm.
a.R/kB =Avogadro's number.
What is the overall standard free-energy change for the following two reactions? A+B→CΔGrxn°=ΔG1 C+D→EΔGrxn°=ΔG2 a.ΔG1+ΔG2 d.ΔG1ΔG2 b.ΔG1−ΔG2 e.ΔG1/ΔG2 c.ΔG2−ΔG1
a.ΔG1+ΔG2
The reaction A(g) +B(g) →C(g) has the following rate law: Rate =k[A]1/2[B]2. If the concentration of A is quadrupled while the concentration of B is halved, the rate will change by a factor of ________. a.0.25 d.4 b.0.50 e.16 c.2
b) .50
For a particular hypothetical reaction, 2A+B→C, the value of ΔG°is 250 kJ/mol.What is the value of ΔG for this reaction at 298 K when [A] =0.60 M, [B] =0.10 M, and [C] =4.0 ×10−3M? a.248 kJ/mol d.250 kJ/mol b.245 kJ/mol e.255 kJ/mol c.2,775 kJ/mol
b) 245 kJ/mol
Which of the processes A-D will lead to a positive change in the entropy of the system? a.Sodium chloride crystals form as salt water evaporates. b.Helium gas escapes from the hole in a balloon. c.Stalactites form in a cave. d.Water freezes in a freezer. e.All of these lead to a positive change in entropy of the system, because they are all spontaneous.
b) Helium gas escapes from the hole in the balloon.
Which of the following must be true for a reaction to proceed to form products? a.Q>K, ΔG<0, and ΔG°<0 b.Q<Kand ΔG<0, ΔG°can be anything c.Q>Kand ΔG°<0, ΔGcan be anything d.Q<K, ΔG<0, ΔG°<0 e.Q<Kand ΔG°<0, ΔGcan be anything
b) Q<Kand ΔG<0, ΔG°can be anything
For a chemical reaction with a positive enthalpy and negative entropy, predict under which conditions the reaction will be spontaneous. a.The reaction is always spontaneous. b.The reaction is never spontaneous. c.The reaction is spontaneous at high temperatures. d.The reaction is spontaneous at low temperatures. e.Insufficient data is provided to answer this question.
b) The reaction is never spontaneous.
Before class, students were distributed throughout a classroom. When the bell rang, all the students sat down at three tables in the center of the room. The entropy of the class ________ a.increased. d.cannot be determined. b.decreased. e.is irrelevant. c.remained the same.
b) decreased
The linear form of ________ is very useful, as it allows us to calculate the activation energy and the frequency factor. a.the Boltzmann equation d.the rate law b.the Arrhenius equation e.the integrated rate law c.Planck's equation
b) the Arrhenius equation
A scientist conducts an experiment to determine the rate of the following reaction: N2(g)+3H2(g)→2NH3(g) If the initial concentration of H2 was 0.150 M and the concentration of H2 was 0.050 M after 2.10 s, what is the average rate of the reaction? a.0.048 M/s d.0.072 M/s b.0.016 M/s e.0.032 M/s c.0.144 M/s
b. 0.016 M/s
The rate law of a particular reaction was determined to be Rate =k[A][B]. What is the unit of the rate constant for the reaction? a.M/s d.1/s b.1/(Ms) e.Ms c.1/(Ms2)
b. 1/(Ms)
A qualitative interpretation of the effect of temperature on equilibrium views heat as a reactant or product and explains shifts in equilibrium with temperature as responses to stress to the equilibrium. How does van 't Hoff's equation refine this view? a.It incorporates the heat into a RICE table calculation. b.It accounts for the shift in terms of the temperature dependence of K. c.It uses stoichiometry to interpret heat quantitatively as a reactant or product. d.It uses a statistical-mechanical interpretation of heat. e.It enables Qto be calculated from ΔH°and ΔS°.
b.It accounts for the shift in terms of the temperature dependence of K.
Indicate which one of the following reactions results in a negative ΔSsys. a.Br2(l)Br2(g) b.Pb(NO3)2(aq)+2KCl(aq)PbCl2(s)+2KNO3(aq) c.CH3COOH(aq)CH2COO−(aq)+H+(aq) d.4NO2(g)+6H2O(g)4NH3(g)+7O2(g) e.2NaN3(s)2Na(l)+3N2(g)
b.Pb(NO3)2(aq)+2KCl(aq)PbCl2(s)+2KNO3(aq)
Octane can undergo combustion to produce carbon dioxide and water and release tremendous amounts of energy. The balanced chemical equation for this reaction is shown below. How could the rate of this reaction be expressed correctly in terms of the rate at which the concentration of a reactant or product changes? 2C8H18(l)+25O2(g)→18H2O(g)+16CO2(g) a.Rate =−25Δ[O2]/Δt d.Rate =18Δ[H2O]/Δt b.Rate =−125Δ[O2]/Δt e.Rate =Δ[CO2]/Δt c.Rate =−128Δ[H2O]/Δt
b.Rate =−1/25 Δ[O2]/Δt
The reaction A + 2B → C is first order in B and A. The overall order of the reaction is ________ a.first. d.zero. b.second. e.fourth. c.third.
b.second.
The prediction of linearity in a van 't Hoff plot assumes ________ a.that the reaction is run under ideal conditions. b.that ΔH°and ΔS°are independent of temperature. c.that ΔG°is independent of temperature. d.that ln Kis independent of temperature. e.none of the above.
b.that ΔH°and ΔS°are independent of temperature.
At constant Tand P, any reaction will be spontaneous if ________ a.ΔGsys>0. d.ΔSsys<0. b.ΔGsys<0. e.ΔHsys<0. c.ΔSsys>0.
b.ΔGsys<0.
Indicate which of the following has the smallest standard molar entropy (S°). a.NH3(g) d.Hg(l ) b.H2O(l) e.Ar(g) c.Mg(s)
c) Mg(s)
The symbol ΔGf°(NH4NO3, s) refers to which of the following reactions?a.NH4NO3(g)→NH4NO3(s) b.3NO2(g)+NH3(g)+5/2H2(g)→2NH4NO3(s) c.N2(g)+2H2(g)+3/2O2(g)→NH4NO3(s) d.2N2(g)+4H2(g)+3O2(g)→2NH4NO3(s) e.N2H4(l)+1/5O2(g)→NH4NO3(s)
c) N2(g)+2H2(g)+3/2O2(g)→NH4NO3(s)
According to the second law of thermodynamics, the change in the entropy of the universe (ΔSuniv) during a spontaneous reaction is ________ a.zero. b.negative. c.positive. d.less than the change in entropy of the system (ΔSsys). e.greater than the change in entropy of the system (ΔSsys).
c) Positive
The mechanism for the reaction 2H2O2(aq)→2H2O(l)+O2(g)in the presence of I−(aq) is proposed to be: Step 1: H2O2(aq)+I−(aq)→H2O(l)+OI−(aq)(slow) Step 2: H2O2(aq)+OI−(aq)→H2O(l)+O2(g)+I−(aq)(fast) What is the rate law for the overall reaction? a.Rate =k[H2O2] d.Rate =k[H2O2][OI−] b.Rate =k[H2O2]2 e.Rate =k[H2O2]2[I−]/[H2O] c.Rate =k[H2O2][I−]
c) Rate =k[H2O2][I−]
For the following endothermic reaction, predict under which conditions the reaction will be spontaneous.CaCO3(s)→CaO(s)+CO2(g) a.The reaction is always spontaneous. b.The reaction is never spontaneous. c.The reaction is spontaneous at high temperatures. d.The reaction is spontaneous at low temperatures. e.Insufficient data is provided to answer this question.
c) The reaction is spontaneous at high temperatures.
The reaction 2NO(g) +O2(g) →2NO2(g) has the following rate law: Rate =k[O2][NO]2. If the concentration of NO is reduced by a factor of two, the rate will ________ a.double. d.be reduced by one-half. b.quadruple. e.remain the same. c.be reduced by one-quarter.
c) be reduced by one quarter
In a spontaneous process, which of the following always increases?a.the entropy of the system b.the entropy of the surroundings c.the entropy of the universe d.the entropy of the system and the universe e.the entropy of the system, the surroundings, and the universe
c) the entropy of the universe
For a chemical reaction that is notspontaneous, it is found that ΔSsys>0. Which of the following could be true? a.ΔSsurr<0 and its magnitude is less than ΔSsys. b.ΔSsurr>0 and its magnitude is less than ΔSsys. c.ΔSsurr<0 and its magnitude is greater than ΔSsys. d.ΔSsurr>0 and its magnitude is greater than ΔSsys. e.ΔSuniv>0
c) ΔSsurr<0 and its magnitude is greater than ΔSsys
The second-order reaction A →B is found to have a rate constant of 0.978 M−1s −1. What is the half-life of this reaction when [A]0=0.0300 M? a.0.0293 s d.60.1 s b.0.710 s e.24.3 s c.34.1 s
c. 34.1 s
If 1 mol of ice melts at its melting point of 273 K, the entropy change for the ice is 22.0 J/K. If the ice melts in someone's hand at 34°C, what is the change in the entropy of the universe? Assume a final temperature for the water of 0°C. The enthalpy of fusion for ice is 6.01 kJ/mol. a.+19.6 J/K d.−2.4 J/K b.−19.6 J/K e.+41.5 J/K c.+2.4 J/K
c.+2.4 J/K
For the rate law Rate = k[A][B]1/2, the partial order with respect to A is ________, the partial order with respect to B is ________, and the total order is ________. a.0;12;12 b.1;12;1 c.1;12;32 d.1;12;52 e.The orders cannot be determined without a chemical reaction.
c.1;1/2;3/2
The enthalpy of vaporization for toluene (C7H8) is 380.00 kJ/kg, and its boiling point is 110.6°C. What is the entropy change when 0.75 mole of toluene vaporizes at 110.6°C? a.743 J/K d.36.3 J/K b.139 J/K e.253 kJ/K c.68.5 J/K
c.68.5 J/K
Which of the following statements is true about the instantaneous rate for the chemical reaction A →B as the reaction progresses? a.−ΔA/Δtincreases while ΔB/Δtdecreases. b.−ΔA/Δtdecreases while ΔB/Δtincreases. c.Both −ΔA/Δtand ΔB/Δtdecrease. d.Both −ΔA/Δtand ΔB/Δtincrease. e.The answer will vary depending on the reaction mechanism.
c.Both −ΔA/Δtand ΔB/Δtdecrease.
The symbol ΔGf° (MgSO4, s) refers to which of the following reactions? a.MgO(s)+SO3(g)→MgSO4(s) b.MgSO4(g)→MgSO4(s) c.Mg(s)+18S8(s)+2O2(g)→MgSO4(s) d.MgS(s)+2O2(g)→MgSO4(s) e.8Mg(s)+S8(s)+16O2(g)→8MgSO4(s)
c.Mg(s)+18S8(s)+2O2(g)→MgSO4(s)
Collision theory assumes that the rate of a reaction depends on ________ a.the energy of collisions. b.the orientation of colliding molecules. c.the energy of collisions and the orientation of colliding molecules. d.the change in energy between the products and the reactants. e.the change in free energy between the reactants and products.
c.the energy of collisions and the orientation of colliding molecules.
Ammonia gas (NH3) is produced from hydrogen and nitrogen gas according to the following reaction: 3H2(g)+N2(g)→2NH3(g) If the rate of production of ammonia is R(NH3), what is the rate of loss of hydrogen and nitrogen gas, respectively? a.−R(H2) =2/3 R(NH3); −R(N2) =1/2 R(NH3) b.−R(H2) =3/2 R(NH3); −R(N2) =2 R(NH3) c.−R(H2) =3/2 R(NH3); −R(N2) =1/2 R(NH3) d.−R(H2) =2/3 R(NH3); −R(N2) =2 R(NH3) e.−R(H2) =R(NH3); −R(N2) =R(NH3)
c.−R(H2) =3/2 R(NH3); −R(N2) =1/2 R(NH3)
The entropy change of the surroundings, ΔSsurr, is related to heat transfer, q, with respect to the system and temperature T by ________ a.−q/Tsys=ΔSsurr. b.+q/Tsys=ΔSsurr. c.−q/Tsurr=ΔSsurr. d.q/Tsurr=ΔSsurr. e.None of these, unless the system undergoes a reversible process.
c.−q/Tsurr=ΔSsurr.
The rate of a reaction is found to double when the concentration of one reactant is quadrupled. The order of the reaction with respect to this reactant is ________ a.1. d.1/2. b.2. e.3. c.1/4.
d) 1/2
N2O5 is used as a source of NO2in chemical reactions. The compound decomposes in a first order reaction. If the initial concentration of N2O5=0.400 M, and the concentration is 0.025 Mafter 120 seconds, what is the rate constant kof the reaction? a.7.50 s−1 d.2.31 ×10−2 s−1 b.333 s−1 e.5.21 ×10−4 s−1 c.2.77 s−1
d) 2.31 x 10-2
Hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to form sodium chloride (NaCl) and water. If ΔH°=−56.13 kJ/mol and ΔS°=79.11 J/mol ⋅K, what is the temperature of the reaction if ΔG°=−80.89 kJ/mol? a.154°C d.40.0°C b.313°C e.75°C c.0.313°C
d) 40 C
Which of the following is/are true for a reversible process at equilibrium? I. ΔSuniv=0 II. ΔSsys=0 III. ΔGsys=0 a.I only d.I and III only b.II only e.I, II, and III are all true. c.III only
d) I and III only
The mechanism for the reaction 2H2O2(aq)→2H2O(l)+O2(g)in the presence of I−(aq) is proposed to be: Step 1: H2O2(aq)+I−(aq)→H2O(l)+OI−(aq) Step 2: H2O2(aq)+OI−(aq)→H2O(l)+O2(g)+I−(aq) Which of the following species is an intermediate? a.I− d.OI− b.H2O2 e.This mechanism has no intermediates. c.H2O
d) OI-
For the following exothermic reaction, predict under which conditions the reaction will be spontaneous. 2Mg(s)+O2(g)→2MgO(s) a.The reaction is always spontaneous. b.The reaction is never spontaneous. c.The reaction is spontaneous at high temperatures. d.The reaction is spontaneous at low temperatures. e.Insufficient data is provided to answer this question.
d) The reaction is spontaneous at low temperatures
A chemist is planning to study a chemical equilibrium for which no measured explicit thermodynamic values are available. However, the reaction involves common chemical species. What information could a chemist use to make predictions about the equilibrium? a.equilibrium constants for the equilibrium reactions that can be combined to make the new equilibrium b.ΔGf°values for the reactants and products of the new reaction c.ΔHf and S°values for the reactants and products of the new reaction d.all of the above
d) all of the above
During a spontaneous chemical reaction, it is found that ΔSsys<0. This means ________ a.ΔSsurr<0 and its magnitude is <ΔSsys. b.ΔSsurr<0 and its magnitude is >ΔSsys. c.ΔSsurr>0 and its magnitude is <ΔSsys. d.ΔSsurr>0 and its magnitude is >ΔSsys. e.an error has been made, because Ssys>0 by necessity for a spontaneous process.
d) ΔSsurr>0 and its magnitude is >ΔSsys.
In a rate law, the partial orders are determined by ________ a.the reactant concentrations. b.the stoichiometric coefficients. c.the product concentrations. d.experiment. e.the difference between the forward and reverse rates.
d. experiment
The reaction CHCl3(g) + Cl2(g) → CCl4(g) +HCl(g) has the following rate law: Rate =k[CHCl3][Cl2]. If the concentration of CHCl3is increased by a factor of five while the concentration of Cl2is kept the same, the rate will ________ a.double. d.increase by a factor of five. b.triple. e.decrease by a factor of one-fifth. c.stay the same.
d. increase by a factor of five
The standard entropy of nitrogen gas in air is 192 J/(mol ⋅K). Estimate how many states are accessible to a nitrogen molecule in air. a.3.1 ×1016 d.1.0 ×1010 b.1.0 ×107 e.1.2 ×1023 c.6.0 ×1023
d.1.0 ×1010
At what temperature does the Fe(s) Fe(g) phase transition occur? ΔH=415.5 kJ/mol; ΔS=153.4 J/mol K. a.2,162°F d.4,416°F b.2,435°F e.2,709°F c.4,352°F
d.4,416°F
One reaction that occurs in an automobile catalytic converter is the conversion of nitrogen monoxide to nitrogen and oxygen. How could the rate of this reaction be expressed correctly in terms of the rate at which the concentration of a reactant or product changes? 2NO(g) →N2(g) +O2(g) a.Rate =Δ[NO]/Δt d.Rate =−12Δ[NO]/Δt b.Rate =−Δ[NO]/Δt e.Rate =2Δ[NO]/Δt c.Rate =12Δ[NO]/Δt
d.Rate =−1/2 Δ[NO]/Δt
What is the difference between ΔGand ΔG°? a.ΔG°refers to the formation of a compound from its elements; ΔGcan be defined for any reaction. b.ΔG°refers to the formation of a pure compound; ΔGcan be defined for an impure compound. c.ΔG°refers to a reaction that goes to completion; ΔGis defined for a reaction that goes to any extent. d.ΔG°refers to the conversion of reactants in their standard state to products in their standard state; ΔGis defined for a reaction under any conditions. e.ΔG°refers to reactions of one mole quantities of reactants; ΔGis defined for any quantity of reactants.
d.ΔG°refers to the conversion of reactants in their standard state to products in their standard state; ΔG is defined for a reaction under any conditions.
Processes are always spontaneous when ________ (Hand Srefer to the system). a.ΔH>0 and ΔS <0 b.ΔH<0 and ΔS<0 c.ΔH>0 and ΔS>0 d.ΔH<0 and ΔS>0 e.None of these is true, because temperature must always be taken into account.
d.ΔH<0 and ΔS>0
Care must be taken when dissolving solid pellets of sodium hydroxide (NaOH) in water, because the temperature of the water can rise dramatically. Taking NaOH as the system, what can you deduce about the signs of the entropy change of the system (ΔSsys) and surroundings (ΔSsurr) from this? a.ΔSsys<0 and ΔSsurr<0 b.ΔSsys<0 and ΔSsurr>0 c.ΔSsys>0 and ΔSsurr<0 d.ΔSsys>0 and ΔSsurr>0 e.Nothing can be deduced from this limited information.
d.ΔSsys>0 and ΔSsurr>0
Chlorine dioxide (ClO2) is used as a disinfectant in municipal water-treatment plants. It decomposes in a first-order reaction with a rate constant of 0.0714 s−1. If the initial concentration were 0.12 M, what would the concentration be after 14.0 s has elapsed? a.0.033 M d.0.012 M b.0.12 M e.0.044 M c.0.060 M
e) 0.044 M
Calculate the equilibrium constant at 500 K for the following reaction given the data below. N2(g)+3H2(g)2NH3(g)Kc (298 K) =6.1 ×105ΔGf°(NH3, g) =−16.5 kJ/molΔHf°(NH3, g) =−46.1 kJ/mol a.53 d.5.4 ×10−4 b.1,800 e.332 c.7.5
e) 332
A scientist conducts an experiment to determine the rate of the following reaction: N2(g)+O2(g)→2NO(g) If the initial concentration of NO was 0.00 M and the concentration of NO was 0.050 M after 0.100 s, what is the average rate of the reaction? a.0.500 M/s d.10.0 M/s b.1.00 M/s e.0.250 M/s c.5.00 M/s
e. 0.250 M/s
In a first order reaction, the initial concentration of A is 0.40 M. What is the concentration of A after 15 seconds if the half-life of the reaction is 3 seconds? a.8.0 ×10−2M d.2.5 ×10−2M b.2.0 M e.1.3 ×10−2M c.5.0 ×10−2M
e. 1.3 x 10-2M
The equilibrium constant for a reaction is determined at several temperatures by measuring concentrations of reactants and products. To determine the standard enthalpy and entropy changes for the reactions, you need to plot ________ on the y-axis and ________ on thex-axis and fit the data to a linear equation. The slope of this line is equal to ________, and the intercept provides a value for ________. a.K; T; −ΔH°/R; ΔS°/i d.ln(K); 1/T; ΔS°/R; ΔH°/R b.ln(K); 1/T; ΔH°; ΔS° e.ln(K); 1/T; −ΔH°/R; ΔS°/R c.ln(K); 1/T; ΔH°/R; ΔS°/R
e.ln(K); 1/T; −ΔH°/R; ΔS°/R
NO2 contributes to the brown haze associated with photochemical smog events. When is NO2 concentration highest? a) in the morning before rush hour b) in the morning after rush hour c) in midmorning d) noon e) midafternoon
midmorning
