Q&A Hero

Q: The reaction below is second order in ClO2 and first order in OH-. If the rate is expressed in M/s, the rate constant, k, has the units ________.2 ClO2(aq) + 2 OH-(aq) -> ClO3-(aq) + ClO2-(aq) + H2O(l)

Q: A reaction has the rate law Rate = k[NO]2[H2]. If the concentration of NO is reduced by half and the concentration of H2 is quadrupled, the rate of reaction will ________ (increase, decrease, not change).

Q: A reaction has the rate law Rate = k[NO]2[H2]. If the concentration of NO is reduced by 1/3, the rate of reaction will be ________ (increased, decreased) by ________.

Q: The reaction shown below has the rate law: Rate = k[BrO3-][Br-][H+]2. The order of reaction with respect to H+ is ________ and the overall order is ________.BrO3-(aq) + 5 Br-(aq) + 6 H+(aq) -> 3 Br2(aq) + 3 H2O(l)

Q: The reaction below is first order in H2 and one-half order in Br2. The rate law for this reaction is ________.H2(g) + Br2(g) -> 2 HBr(g)

Q: For the reaction shown below, if the rate of formation of Br2 is 1.2 10-6 M/s, over the same time period the rate of consumption of H+ is ________ M/s.ClO2-(aq) + 4 Br-(aq) + 4 H+(aq) -> Cl-(aq) + 2 Br2(aq) +2 H2O(l)

Q: For the reaction shown below, the rate of reaction of Br- is ________ times the rate of formation of Br2over the same time period.ClO2-(aq) + 4 Br-(aq) + 4 H+(aq)-> Cl-(aq) + 2 Br2(aq) +2 H2O(l)

Q: For the reaction shown below, if the rate of formation of O2 is 6.0 10-6 M/s, the rate of decomposition of N2O5 over the same time interval is ________.2 N2O5(g) ->4 NO2(g) + O2(g)

Q: The aquation of tris(1,10-phenanthroline)iron(II) in acid solution takes place according to the equation:Fe(phen)32+ + 3 H3O+ + 3 H2O -> Fe(H2O)62+ + 3 phenH+.If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30C is 9.8 10-3 min-1, what is the rate constant at 35C?A) 4.4 10- 3 min-1B) 2.2 10- 2 min-1C) 4.5 101 min-1D) 2.3 102 min-1

Q: Hydrogen iodide decomposes at 800 K via a second-order process to produce hydrogen and iodine according to the following chemical equation.2 HI(g) -> H2(g) + I2(g)At 800 K it takes 142 seconds for the initial concentration of HI to decrease from 6.75 10-2 M to 3.50 10-2 M. What is the rate constant for the reaction at this temperature?A) 5.12 10-4 M-1s-1B) 9.69 10-2 M-1s-1C) 10.3 M-1s-1D) 1.95 103 M-1s-1

Q: Nitrogen dioxide decomposes at 300C via a second-order process to produce nitrogen monoxide and oxygen according to the following chemical equation.2 NO2(g) -> 2 NO(g) + O2(g).A sample of NO2(g) is initially placed in a 2.50-L reaction vessel at 300C. If the half-life and the rate constant at 300C are 11 seconds and 0.54 M-1 s-1, respectively, how many moles of NO2 were in the original sample?A) 0.17 molB) 0.42 molC) 5.9 molD) 15 mol

Q: The second-order reaction 2 Mn(CO)5 -> Mn2(CO)10, has a rate constant equal to3.0 109 M-1 s-1 at 25C. If the initial concentration of Mn(CO)5 is 2.0 10-5 M, how long will it take for 90.% of the reactant to disappear?A) 6.7 10- 16 sB) 7.4 10- 15 sC) 1.5 10- 4 sD) 6.0 103 s

Q: In aqueous solution, hypobromite ion, BrO-, reacts to produce bromate ion, BrO3-, and bromide ion, Br-, according to the following chemical equation. A plot of 1/[BrO-] vs. time is linear and the slope is equal to 0.056 M-1s-1. If the initial concentration of BrO- is 0.80 M, how long will it take one-half of the BrO- ion to react? A) 4.5 10-2 s B) 7.1 s C) 12 s D) 22 s

Q: What percentage of a radioactive substance remains after 7.00 half-lives have elapsed? A) 0.391% B) 0.78% C) 1.56% D) 3.12%

Q: Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239Np to decay to 0.100% of its original quantity? A) 0.0 427 days B) 1.491 days C) 2.04 days D) 23.4 days

Q: For the first-order reaction, 2 N2O(g) -> 2 N2(g) + O2(g), what is the concentration of N2O after 3 half-lives if 0.25 mol of N2O is initially placed into a 1.00-L reaction vessel?A) 1.6 10- 2 MB) 3.1 10- 2 MC) 6.2 10- 2 MD) 1.2 10- 1 M

Q: The first-order reaction, SO2Cl2 -> SO2 + Cl2, has a half-life of 8.75 hours at 593 K. How long will it take for the concentration of SO2Cl2 to fall to 16.5% of its initial value?A) 0. 143 hrB) 2.28 hrC) 6.99 hrD) 22.7 hr

Q: The rate constant, k, for a first-order reaction is equal to 4.2 10-4 s-1. What is the half-life for the reaction? A) 2.9 10-4 s B) 1.2 103 s C) 1.7 103 s D) 2.4 103 s

Q: The following reaction is first order, C2H6 -> 2 CH3. If the rate constant is equal to 5.5 10-4 s-1 at 1000 K, how long will it take for 0.35 mol of C2H6 in a 1.00 L container to decrease to 0. 20 mol in the same container?A) 4.5 minB) 17 minC) 53 minD) 65 min

Q: The isomerization reaction, CH3NC -> CH3CN, is first order and the rate constant is equal to0.46 s-1 at 600 K. What is the concentration of CH3NC after 0.20 minutes if the initial concentration is 0. 30 M?A) 1.2 10- 3 MB) 2.7 10- 3 MC) 1.2 10- 1 MD) 2.7 10- 1 M

Q: The first-order reaction, 2 N2O(g) -> 2 N2(g) + O2(g), has a rate constant equal to 0.76 s-1 at1000 K. How long will it take for the concentration of N2O to decrease to 12% of its initial concentration?A) 0. 62 sB) 2.8 sC) 6.3 sD) 8.4 s

Q: The first-order reaction, SO2Cl2 -> SO2 + Cl2, has a rate constant equal to 2.20 10-5 s-1 at 593 K. What percentage of the initial amount SO2Cl2 will remain after 6.00 hours?A) 1.00%B) 37.8%C) 40.2%D) 62.2%

Q: For a particular first-order reaction, it takes 24 minutes for the concentration of the reactant to decrease to 25% of its initial value. What is the value for rate constant (in s-1) for the reaction? A) 2.0 10- 4 s-1 B) 9.6 10- 4 s-1 C) 1.2 10- 2 s-1 D) 5.8 10- 2 s-1

Q: What is the overall reaction order for the reaction that has the rate law: Rate = k[ O2] [ NO]2? A) zero order B) first order C) second order D) third order

Q: For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of reaction if the concentration of B is increased by a factor of 3.00? The rate will A) decrease by a factor of 1/ 9.00. B) decrease by a factor of 1/ 3.00. C) increase by a factor of 3.00. D) increase by a factor of 9.00.

Q: For a reaction that follows the general rate law, Rate = k[A][B]2, what will happen to the rate of reaction if the concentration of A is increased by a factor of 5.00? The rate will A) decrease by a factor of 1/ 25.0. B) decrease by a factor of 1/ 5.00. C) increase by a factor of 5.00. D) increase by a factor of 25.0.

Q: The decomposition of dinitrogen pentoxide is described by the chemical equation2 N2O5(g) -> 4 NO2(g) + O2(g)If the rate of appearance of O2 is equal to 3.00 mol/min at a particular moment, what is the rate of disappearance of N2O5 at that moment?A) 0. 750 mol/minB) 1. 50 mol/minC) 6.00 mol/minD) 12.0 mol/min

Q: The decomposition of dinitrogen pentoxide is described by the chemical equation2 N2O5(g) -> 4 NO2(g) + O2(g)If the rate of appearance of NO2 is equal to 0.560 mol/min at a particular moment, what is the rate of appearance of O2 at that moment?A) 0.140 mol/minB) 0.280 mol/minC) 1.12 mol/minD) 2.24 mol/min

Q: The decomposition of dinitrogen pentoxide is described by the chemical equation2 N2O5(g) -> 4 NO2(g) + O2(g)If the rate of disappearance of N2O5 is equal to 1.60 mol/min at a particular moment, what is the rate of appearance of NO2 at that moment?A) 0.800 mol/minB) 1.60 mol/minC) 3.20 mol/minD) 6.40 mol/min

Q: The reaction that occurs in a Breathalyzer, a device used to determine the alcohol level in a person's bloodstream, is given below. If the rate of appearance of Cr2(SO4)3 is 1.64 mol/min at a particular moment, what is the rate of disappearance of C2H6O at that moment? A) 0. 547 mol/min B) 1.09 mol/min C) 2.46 mol/min D) 4.92 mol/min

Q: What is the activation energy for the destruction of ozone?A) 14 kJB) 392 kJC) 406 kJD) none of these

Q: What is the activation energy for the formation of ozone? A) 14 kJ B) 392 kJ C) 406 kJ D) none of these

Q: Intermediates occur at which reaction stages? A) reaction stages 1 and 5 B) reaction stages 2, 3, and 4 C) reaction stages 2 and 4 D) reaction stage 3

Q: Transition states occur at which reaction stages? A) reaction stages 1 and 5 B) reaction stages 2, 3, and 4 C) reaction stages 2 and 4 D) reaction stage 3

Q: The energy of reaction, E, is given by the difference in energy between which two reaction stages?A) reaction stage 2 reaction stage 1B) reaction stage 2 reaction stage 3C) reaction stage 1 reaction stage 3D) reaction stage 3 reaction stage 1

Q: The activation energy for the forward reaction is given by the difference in energy between which two reaction stages?A) reaction stage 2 reaction stage 1B) reaction stage 2 reaction stage 3C) reaction stage 1 reaction stage 3D) reaction stage 3 reaction stage 1

Q: What is the species present at reaction stage 3? A) an intermediate B) a product C) a reactant D) a transition state

Q: Calculate the freezing point of a solution of 20.0 g methyl salicylate, C7H6O2, dissolved in 800. g of benzene, C6H6. Kf for benzene is 5.10C/m and the freezing point is 5.50C for benzene. A) -1.05C B) 1.05C C) 4.45C D) 6.54C

Q: What is the expected freezing point of a 0.50 m solution of Na2SO4 in water? Kf for water is 1.86C/m. A) -0.93C B) -1.9C C) -2.8C D) -6.5C

Q: Which of the following pairs of solutions have roughly the same boiling point elevation? A) 0.100 m C6H12O6 and 0.0333 m CuCl2 B) 0.100 m NaCl and 0.100 m C6H12O6 C) 0.200 m NaCl and 0.300 m Na2SO4 D) 0.100 m KCl and 0.0500 m MgBr2

Q: Which of the following solutions will have the lowest freezing point? A) 0.0100 m NaCl B) 0.0100 m Li2SO4 C) 0.035 m CH3CH2CH2OH D) 0.015 m MgCl2

Q: A 0.020 m aqueous solution containing which solute will have the lowest freezing point? A) LiCl B) NaCl C) KCl D) All will have approximately the same freezing point.

Q: A 0.50 m solution of which solute has the largest van't Hoff factor? A) CaCl2 B) K3PO4 C) LiCO3 D) NaNO3

Q: When 2.36 g of a nonvolatile solute is dissolved in 100 g of solvent, the largest change in freezing point will be achieved when the solvent is A) benzene, Kf = 5.07. B) camphor, Kf = 37.8. C) chloroform, Kf = 4.70. D) All are expected to have the same freezing point.

Q: If one mole of each is dissolved in 1.00 L of water, which will lower the vapor pressure the most? A) C12H22O11 B) NaNO3 C) C3H7OH D) MgCl2

Q: How many grams of sucrose, C12H22O11, must be added to 500. g of water at 100C to change the vapor pressure to 752 mm Hg? A) 0.295 g B) 5.32 g C) 10.6 g D) 101 g

Q: At a given temperature the vapor pressures of benzene and toluene are 183 mm Hg and 59.2 mm Hg, respectively. Calculate the mole fraction of benzene in the vapor phase over a solution of benzene and toluene with Xbenzene = 0.600. A) 0.600 B) 0.678 C) 0.756 D) 0.823

Q: At a given temperature the vapor pressures of benzene and toluene are 183 mm Hg and 59.2 mm Hg, respectively. Calculate the total vapor pressure over a solution of benzene and toluene with Xbenzene = 0.600. A) 110 mm Hg B) 121 mm Hg C) 133 mm Hg D) 242 mm Hg

Q: A KCl solution is prepared by dissolving 40.0 g KCl in 250.0 g of water at 25C. What is the vapor pressure of the solution if the vapor pressure of water at 25C is 23.76 mm Hg? A) 20.5 mm Hg B) 22.1 mm Hg C) 22.9 mm Hg D) 25.5 mm Hg

Q: Which of the following is not an application of colligative properties? A) adding silver to mercury to lower the vapor pressure of mercury B) desalinating sea water by reverse osmosis C) melting snow by application of salt D) reduced boiling points of pure liquids at increased altitudes

Q: The solubility of argon in water at 25C is 0.0150 mol/L. What is the Henry's Law constant for argon if the partial pressure of argon in air is 0.00934 atm?A) 1.40 10-4 mol/(L atm)B) 0.623 mol/(L atm)C) 1.61 mol/(L atm)D) 4.10 mol/(L atm)

Q: The Henry's Law constant of methyl bromide, CH3Br, is k = 0.159 mol/(L atm) at 25C. What is the solubility of methyl bromide in water at 25C and at a partial pressure of 250. mm Hg?A) 0.0523 mol/LB) 0.329 mol/LC) 0.483 mol/LD) 39.8 mol/L

Q: In which case should CO2(g) be more soluble in water? A) The total pressure is 5 atm and the partial pressure of CO2 is 1 atm. B) The total pressure is 3 atm and the partial pressure of CO2 is 2 atm. C) The total pressure is 1 atm and the partial pressure of CO2 is 0.03 atm. D) The total pressure is 1 atm and the partial pressure of CO2 is 0.5 atm.

Q: The solubility of gaseous solutes in liquid solvents is greater when the A) external pressure over the solution is increased. B) external pressure is decreased. C) partial pressure of the gas above the solution is increased. D) partial pressure of the solvent is increased.

Q: In general, as the temperature increases, the solubility of gases in water ________ and the solubility of most solids in water ________. A) decreases, decreases B) decreases, increases C) increases, decreases D) increases, increases

Q: Which of the following statements is true for a supersaturated solution? A) The solute in the solution is at equilibrium with undissolved solute. B) The solution contains more than the equilibrium amount of solute. C) The solution is stable and the solute will not precipitate. D) A supersaturated solution is more than 50% solute by mass.

Q: Which of the following does not affect the solubility of a solute in a given solvent? A) polarity of the solute B) polarity of the solvent C) rate of stirring D) temperature of the solvent and solute

Q: A saturated solution is defined as A) a concentrated solution. B) a solution that is in equilibrium with pure solvent. C) a solution than is in equilibrium with undissolved solute. D) a solution that is in equilibrium with both pure solvent and undissolved solute.

Q: At 25.0C, a solution has a concentration of 3.179 M and a density of 1.260 g/mL. The density of the solution at 50.0C is 1.249 g/mL. What is the molarity of the solution at 50.0C? A) 2.545 M B) 3.151 M C) 3.179 M D) 3.230 M

Q: A solution of LiCl in water is 18.0 wt% LiCl. What is the mole fraction of LiCl? A) 0.0853 B) 0.0933 C) 0.425 D) 4.56

Q: A solution of LiCl in water has XLiCl = 0.0500. What is the molality? A) 2.60 m LiCl B) 2.77 m LiCl C) 2.92 m LiCl D) 5.26 m LiCl

Q: A 2.00 M solution of CaCl2 in water has a density of 1.17 g/mL. What is the mole fraction of CaCl2? A) 0.0348 B) 0.0360 C) 0.0366 D) 0.0380

Q: A 3.17 m solution of CaCl2 in water has a density of 1.24 g/mL. What is the molarity? A) 2.56 M CaCl2 B) 2.91 M CaCl2 C) 3.50 M CaCl2 D) 3.93 M CaCl2

Q: A 1.30 M solution of CaCl2 in water has a density of 1.11 g/mL. What is the molality? A) 1.17 m CaCl2 B) 1.25 m CaCl2 C) 1.35 m CaCl2 D) 1.44 m CaCl2

Q: Sodium hydroxide is available commercially as a 50.0% by weight aqueous solution. Calculate the molality of this sodium hydroxide solution. A) 0.450 m B) 19.1 m C) 25.0 m D) 125. m

Q: Sodium hydroxide is available commercially as a 50.0% by weight aqueous solution. The density of the solution is 1.53 g/mL. Calculate the molarity of this sodium hydroxide solution. A) 0.450 M B) 19.1 M C) 25.0 M D) 125. M

Q: Aqueous solutions of 30.0% (by weight) hydrogen peroxide, H2O2, are used to oxidize metals or organic molecules in chemical reactions. Calculate the molality of this solution. A) 0.974 m B) 6.78 m C) 9.79 m D) 12.6 m

Q: Aqueous solutions of 30% (by weight) hydrogen peroxide, H2O2, are used to oxidize metals or organic molecules in chemical reactions. Given that the density of the solution is 1.11 g/mL, calculate the molarity. A) 0.794 M B) 6.78 M C) 9.79 M D) 12.6 M

Q: How many grams of KBr are required to make 650. mL of a 0.115 M KBr solution? A) 0.628 g B) 5.65 g C) 8.90 g D) 74.8 g

Q: A solution is 2.25% by weight NaHCO3. How many grams of NaHCO3 are in 450.0 g of solution? A) 0.500 g B) 10.1 g C) 200 g D) 225 g

Q: What molality of pentane is obtained by dissolving 5.0 g pentane, C5H12, in 245.0 g hexane, C6H14? A) 0.020 m B) 0.024 m C) 0.28 m D) 20. m

Q: To make a 2.0 M solution, one could take 2.00 moles of solute and add A) 1.00 L of solvent. B) 1.00 kg of solvent. C) enough solvent to make 1.00 L of solution. D) enough solvent to make 1.00 kg of solution.

Q: How much water must be added to 42.0 g of CaCl2 to produce a solution that is 35.0 wt% CaCl2? A) 56.7 g B) 78.0 g C) 83.3 g D) 120 g

Q: What volume of 3.00 M CH3OH solution is needed to provide 0.270 mol of CH3OH? A) 1.23 mL B) 11.1 mL C) 90.0 mL D) 810 mL

Q: What volume of 0.716 M KBr solution is needed to provide 10.5 g of KBr? A) 7.52 mL B) 14.7 mL C) 63.2 mL D) 123 mL

Q: What is the weight percent of a caffeine solution made by dissolving 4.35 g of caffeine, C8H10N4O2, in 75 g of benzene, C6H6? A) 0.055% B) 0.058% C) 5.5% D) 5.8%

Q: What is the weight percent of vitamin C in a solution made by dissolving 1.30 g of vitamin C, C6H8O6, in 55.0 g of water? A) 0.195% B) 0.242% C) 2.31% D) 2.36%

Q: A solution is prepared by dissolving 171 g of CdCl2 in enough water to make exactly 250.0 mL of solution. If the density of the solution is 1.556 g/mL, what is the weight percent of CdCl2 in the solution? A) 7.17% B) 44.0% C) 56.0% D) 68.4%

Q: A solution is prepared by dissolving 171 g of CdCl2 in enough water to make 250.0 mL of solution. If the density of the solution is 1.556 g/mL, what is the molarity of the solution? A) 0.440 M B) 0.684 M C) 0.933 M D) 3.73 M

Q: A solution is prepared by dissolving 17.75 g sulfuric acid, H2SO4, in enough water to make exactly 100.0 mL of solution. If the density of the solution is 1.1094 g/mL, what is the weight % H2SO4 in the solution? A) 16.00% B) 18.00% C) 19.00% D) 84.00%