AP Chemistry Mid Term Multiple Choice

A reaction has a very large Keq of 3.3 x 1013. Which statement is true about this reaction A. The reaction is very fast B. The reaction is essentially complete C. Both of the above D. Neither of the above.

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Which of the following is the LEAST effective in increasing the rate of a reaction? A. increasing the pressure by adding an inert gas B. grinding a solid reactant into small particles C. increasing the temperature D. eliminating the reverse reactions E. adding a catalyst

a

A chemical system in equilibrium will A. have the same concentrations of all products and reactants B. form more products if the temperature is increased C. have a specific ratio of product to reactant concentrations D. not have any precipitates E. be a slow reaction

c

A first - order reaction has a half - life of 85 s. What fraction of the reactant is left after 255 s? A. 1/2 B. 1/4 C. 1/8 D. 1/3 E. 7/8

c

In the gas phase reaction below, is acting as a(n) __________ base but not as a(n) __________ base. NH3+ H--> NH4 A) Arrhenius, Br nsted-Lowry B) Br nsted-Lowry, Lewis C) Lewis, Arrhenius D) Lewis, Br nsted-Lowry E) Arrhenius, Lewis

c

This is the correct term to use to determine if a system has come to equilibrium A. Ka and Q B. Kc C. Q and Le Chatelier's Principle D. Q E. Le Chatelier's Principle

c

For which salt should the aqueous solubility be most sensitive to pH? A)Ca(NO3)2 B) CaF2 C)CaCl2 D) CaBr2 E) CaI2

d

The mechanism for formation of the product X is: A + B ------> C + D (slow) B + D ----> X (fast) The intermediate reactant in the reaction is _____ A. A. B. B C. C D. D E. E

d

Which ion is the strongest base? A. Cu(NH3)4 +2 B. KOH C. HCO3 -1 D. CO3 -2 E. SO3 -2

d

An Arrhenius plot is a graph of A. the rate constant vs. concentration B. the natural logarithm (ln) of the rate constant vs. ln T C. the reciprocal of the rate constant vs. T D. the rate constant vs. ln(1/T) E. the natural logarithm (ln) of the rate constant vs. 1/T

e

In which of the following cases is the reaction expected to be exothermic? A. Increasing the pressure increases the amount of product formed B. Increasing the amount of reactants increases the amount of product formed C. Increasing the temperature increases the amount of product formed D. Increasing the volume decreases the amount of product formed E. Increasing the temperature decreases the amount of product formed.

e

Which solution below has the highest concentration of hydroxide ions? A) pH = 3.21 B) pH = 12.6 C) pH = 7.93 D) pH = 9.82 E) pH = 7.00

e

the transistion state theory involves a. activation energy and potential energy curve b. orientation c.potential energy curve and orientation d.frequency e. activation complex potential energy curve, and activation energy

e

A buffer at pH 5.32 is prepared from a weak acid with a pKa = 5.15. If 100mL of this buffer is diluted to 200mL with distilled water, the pH of the dilute solution is A. 5.62 B. 5.02 C. 5.32 D. The identity of the acid is needed to answer this question E. The concentrations of the acid and the salt are needed to answer this question

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A buffer with a pH of 10.0 is needed. Which of the following should be used? \A. acetic acid with a Ka of 1.8 x 10-5 B.ammonia with a Kb of 1.8 x 10-5 C. nitrous acid with a Ka of 7.1 x 10-4 D.H2PO4- and PO43- with a Ka of 4.5 x 10-13 E. dimethylamine with a Ka of 15 x 10-3

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A catalyst can increase the rate of a reaction by A. changing the value of the frequency factor (A) B. by providing a pathway with a lower activation energy C. Both D. Neither

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A possible mechanism for the overall reaction: Br2(g) + 2NO(g) ----> 2NOBr(g) is The rate law for formation of NOBr based on this mechanism is rate = _______________ A. k1[NO]1/2 B. K1[Br2]1/2 C. (k2k1/k-1) [NO]2[Br2] D. (k1/k-1)2[NO]2 E. (k2k1/k-1) [NO]2[Br2]2

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For the reaction: 2NO2(g) ↔ N2O4(g) Kp = 8.8 when pressures are measured in atmospheres. Under which of the following conditions will the reaction proceed in the forward direction? NO2(g) N2O4(g) A. 0.200 atm 0.352 atm B. 250 mm Hg 400 mm HG C. 0.00255 atm 0.000134 atm D. 46.5 mm HG 82.3 mm Hg E. 0.128 atm 0.764 atm

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For which of the following will Kp = Kc? A. MgCO3(s) + 2HCL (g) ↔ MgCl2 (s) + CO2(g) + H2O (l) B. C(s) + O2 ↔ CO (g) C. CH4(g) + 3O2 (g) ↔ CO2 (g) + 2H2O (g) D. Zn(s) + 2HCl (aq) ↔ H2 (g) + ZnCl2 (aq) E. 2NO2 + O2 (g) ↔ N2O5 (g)

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Given the reaction: C2H4 (g) + H2 (g) ---> C2H6 (g) (which is an addition reaction) H° = -137 kJ Account for the following observations regarding the exothermic reaction represented by the equation above. (a) An increase in the pressure of the reactants causes an increase rate. (b) A small increase in temperature causes a large increase in the reaction rate. (c) The presence of metallic nickel causes an increase in reaction rate. (d) The presence of powdered nickel causes a larger increase in reaction rate than does the presence of a single pieces of nickel of the same mass.

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In which of the following cases is the reaction expected to be exothermic? A. Increasing the pressure increases the amount of product formed B. Increasing the amount of reactants increases the amount of product formed C. Increasing the temperature increases the amount of product formed D. Increasing the volume decreases the amount of product formed E. Increasing the temperature decreases the amount of product formed.

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The equilibrium constant for the reaction H2(g) + I2(g) ↔ 2HI (g) must be determined. If 1.00 g of HI is placed in a 2.00 L flask, which of the following is LEAST important in determining the equilibrium constant? A. The temperature must remain constant at the desired value B. Several measurements must be made to assure that the reaction is at equilibrium C. Only one of the three concentrations needs to be accurately determined D. All three concentrations must be accurately measured E. The original mass and volume of the flask must be accurately measured.

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The ph of a 0.125 M solution of a weak base is 10.45. What is the pKb of the base? A. 3.5 x 10-11 B.6.4 x 10-7 C. 2.8 x 10-4 D.2.3 x 10-3 E. 1.2 x 10-2

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The rate law of the overall reaction: A + B ----> C is rate = k[A]2. Which of the following will not increase the rate of the reaction? A. increasing the concentration of reactant A B. increasing the concentration of reactant B C. increasing the temperature of the reaction D. adding a catalyst for the reaction E. All of the above will increase the rate

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When 0.250 mol of NaOH is added to 1.00 L of 0.100 M H3PO4, the solution will contain A. HPO4-2 B.H2PO4- C. PO4-3 D.A and B E. A and C

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Which of the following has the highest pH A. 0.100 M HCl B.0.200 M HC2H3O2 C. 0.100 M Na2CO3 D.0.200 M NaCl E. 0.500 M NaC2H3O2

...

Which of the following is true? A. If we know that a reaction is an elementary reaction, then we know its rate law B. The rate - determining step of a reaction is the rate of the fastest elementary step of its mechanism C. Since intermediate compounds can be formed, the chemical equations for the elementary reactions in a multistep mechanism do not always have to add to give the chemical equation of the overall process D. In a reaction mechanism, an intermediate is identical to an activated complex E. All of the above are true statements

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pH - pKa A. when [conjugate acid] = [conjugate base] B.at the end point of a titration C. in the buffer region D.in the Henderson - Hasselbalch equation E. at equilibrium

...

A fast reaction would have A. a high activation energy B. a catalyst present C. a low activation energy D. an exothermic heat of reactions E. a fast reverse reaction

a

One difference between first - and second - order reactions is that ______________ A. the half - life of a first - order reaction does not depend on [A]0; the half - life of a second - order reaction does depend on [A]0 B. the rate of both first - and second - order reactions do not depend on reactant concentrations C. the rate of a first - order reaction depends on reactant concentrations; the rate of a second - order reaction does not depend on reactant concentrations D. a first order - reaction can be catalyzed; a second order - reaction cannot be catalyzed E. None of the above

a

The conjugate base of is __________. A) OH- B) H2SO4 C) SO4 to the -2 D) HSO4 to the +1 E) H3SO4 to the +1

a

The equilibrium constant depends on the ______ of the reaction l. stoichiometry ll. mechanism lll. quantities of reactants and products present A. l only B. l and ll C. l and lll D. ll and lll E. l, ll, and lll

a

The reaction shown here is exothermic: 2SO2(g) + O2(g) ↔ 2SO3(g). Le Chatelier's principle predicts that_________ will result in an increase in the number of moles of SO3(g) in the reaction vessel A. increasing the pressure B. decreasing the pressure C. increasing the temperature D. removing some oxygen E. increasing the volume of the vessel.

a

What change will be caused by addition of a small amount of HCl to a solution containing fluoride ions and hydrogen fluoride? A) The concentration of hydronium ions will increase significantly. B) The concentration of fluoride ions will increase as will the concentration of hydronium ions. C) The concentration of hydrogen fluoride will decrease and the concentration of fluoride ions will increase. D) The concentration of fluoride ion will decrease and the concentration of hydrogen fluoride will increase. E) The fluoride ions will precipitate out of solution as its acid salt.

a

A first order reaction has a half - life of 36 min. What is the value of the rate constant? A. 3.2 x 10-4 s-1 B. 1.9 x 10-3 L mol-1 s-1 C. 1.2 s-1 D. 0.028 s-1 E. 9.3 x 10-4 L mol-1 s-1

b

A reaction has a very large Keq of 3.3 x 1013. Which statement is true about this reaction A. The reaction is very fast B. The reaction is essentially complete C. Both of the above

b

An aqueous solution contains 0.100 M NaOH at 25.0 °C. The pH of the solution is __________. A) 0.100 B) 1.00 C) 13.00 D) 7.00 E) -1.00

b

As the temperature of a reaction is increased, the rate of a reaction increases because the ____ A. reactant molecules collide more frequently B. reactant molecules collide more frequently and reactant molecules collide with greater energy per collision C. reactant molecules collide more frequently and activation energy is lowered D. reactant molecules collide with greater energy per collision and activation energy is lowered E. reactant moleucles collide more frequently, reactant molecules collide with greater energy per collsion and activation energy is lowered

b

Consider the following equilibrium: 2SO2(g) + O2(g) ↔ 2SO3(g). The equilibrium cannot be established when _____ is/are placed in a 1.0 L container. A. 0.25 mol SO2(g) and 0.25 mol O2(g) B. 0.75 mol SO2(g) C. 0.25 mol SO2(g) and 0.25 mol SO3(g) D. 0.50 mol O2(g) and 0.50 mol SO3(g) E. 1.0 mol SO3(g)

b

For the reaction: 2NO2(g) ↔ N2O4(g) Kp = 8.8 when pressures are measured in atmospheres. Under which of the following conditions will the reaction proceed in the forward direction? NO2(g) N2O4(g) A. 0.200 atm 0.352 atm B. 250 mm Hg 400 mm HG C. 0.00255 atm 0.000134 atm D. 46.5 mm HG 82.3 mm Hg E. 0.128 atm 0.764 atm

b

For which of the following will Kp = Kc? A. MgCO3(s) + 2HCL (g) ↔ MgCl2 (s) + CO2(g) + H2O (l) B. C(s) + O2 ↔ CO (g) C. CH4(g) + 3O2 (g) ↔ CO2 (g) + 2H2O (g) D. Zn(s) + 2HCl (aq) ↔ H2 (g) + ZnCl2 (aq) E. 2NO2 + O2 (g) ↔ N2O5 (g)

b

In which of the following aqueous solutions would you expect AgBr to have the highest solubility? A) 0.10 M LiBr B) 0.10 M C) 0.20 M NaBr D) 0.15 M KBr E) pure water

b

The equilibrium constant for a gas phase reaction is Keq = 4.34 x 10-3 at 573 K. At equilibrium ______ A. products predominate B. reactants predominate C. roughly equal amounts of reactants and products are present D. only products are present E. only reactants are present

b

The magnitude of indicates that __________. A) water autoionizes very slowly B) water autoionizes very quickly C) water autoionizes only to a very small extent D) the autoionization of water is exothermic

b

Which one of the following pairs cannot be mixed together to form a buffer solution? A) NH3, NH4Cl B) NaC2H3O2, HCl (C2H3O2 = acetate) C) RbOH, HBr D) KOH, HF E) H3PO4, KH2PO4

b

A graph of the reciprocal of reactant concentration vs. time will give a straight line for A. a zero - order reaction B. a first - order reaction C. a second - order reaction D. both A and B E. A, B, and C

c

A rate law is found to be Rate = k[A]2[B]. The order of the reaction is A. first order B. second order C. third order D. fourth order E. The rate order cannot be determined

c

A result of the common-ion effect is __________. A) that some ions, such as , frequently appear in solutions but do not participate in solubility equilibria B) that common ions, such as , don't affect equilibrium constants C) that the selective precipitation of a metal ion, such as , is promoted by the addition of an appropriate counterion that produces a compound (AgX) with a very low solubility D) that ions such as and are common ions, so that their values in equilibrium constant expressions are always 1.00 E) that common ions precipitate all counter-ions

c

At 1000.0 K, the equilibrium constant for the reaction 2NO(g) + Br2(g) ↔ 2NOBr(g) is Kp = 0.013. Kp for the reverse reaction is A. 0.013 B. 1.6 x 10-4 C. 77 D. 0.99 E. 1.1

c

If a reactant's concentration is doubled and the reaction rate increases by a factor of 8, the exponent for that reactant in the rate law should be A. 0 B. 1 C. 2 D. 3 E. 1/2

c

Of the following solutions, which has the greatest buffering capacity? A) 0.821 M HF and 0.217 M NaF B) 0.821 M HF and 0.909 M NaF C) 0.100 M HF and 0.217 M NaF D) 0.121 M HF and 0.667 M NaF E) They are all buffer solutions and would all have the same capacity

c

The rate at which CO2 is produced in the reaction: 2C6H6(g) + 15O2(g) -------> 12CO2(g) + 6H2O(l) is 2.2 x 10-2 mol L-1 s-1. What is the rate at which O2 is consumed? A. 2.2 x 10-2 mol L-1 s-1. B. 1.3 x 10-1 mol L-1 s-1. C. 2.8 x 10-2 mol L-1 s-1. D. 1.8 x 10-3 mol L-1 s-1. E. -2.2 x 10-2 mol L-1 s-1.

c

Which of the above is the product of a Lewis acid reacting with a Lewis base? A. Cu(NH3)4 +2, KOH B. KOH C. Cu(NH3)4 +2, HCO3 -1 D. CO3 -2 E. CO3 -2 SO3 -2

c

Which of the following ions will act as a weak base in water? A) OH- B) Cl- C) NO3 - D) ClO- E) None of the above will act as a weak base in water.

c

Which of the following will be most helpful in determining the stability or shelf life of a new drug? A. the reaction mechanism for its decomposition B. the rate law for its decomposition C. the Arrhenius plot of the decomposition reaction D. the integrated rate law plot E. the overall chemical reaction

c

the collision theory involves a. activation energy and potential energy curve b. potential energy curve c.potential energy curve and orientation d.frequency e. activation complex potential energy curve, and activation energy

c

the heat of the reaction is best deduced from the a. activation energy b. orientation c.potential energy curve d.frequency e. activation complex

c

the rate of a chemical reaction is related to a. activation energy and potential energy curve b. orientation c.potential energy curve and orientation d.frequency e. activation complex potential energy curve, and activation energy

c

A rate law is found to be k[A]2[B]. Which of the following actions will NOT change the initial reaction rate? A. doubling the concentrations of both A and B B. doubling the concentration of A and halving the concentration of B C. halving the concentration of A and doubling the concentration of B D. halving the concentration of A and quadrupling the concentration of B E. doubling the concentration of A and quadrupling the concentration of B

d

Addition of a catalyst to the reaction mixture will affect only A. potential energy B. reaction coordinate C. activation energy D. heat of reaction E. nothing

d

At 400 K, the equilibrium constant for the reaction: Br2(g) + Cl2(g) ↔ 2BrCl(g) is Kp = 7.0. A closed vessel at 400 K is charged with 1.0 atm of Br2(g), 1.00 atm Cl2(g), and 2.00 atm of BrCl(g). Which of the statements below is true? A. The equilibrium partial pressures of Br2, Cl2 and BrCl will be the same as the initial values. B. The equilibrium partial pressure of Br2 will be greater than 1.0 atm C. At equilibrium, the total pressure in the vessel will be less than the initial total pressure D. The equilibrium partial pressure of BrCl(g) will be greater than 2.00 atm E. The reaction will go to completion since there are equal amounts of Br2, and Cl2

d

In a solution, when the concentrations of a weak acid and its conjugate base are equal, A) the system is not at equilibrium. B) the buffering capacity is significantly decreased. C) the -log of the and the -log of the are equal. D) all of the above are true.

d

The effect of a catalyst on an equilibrium is to______ A. increase the rate of the forward reaction B. increase the equilibrium constant so that products are favored C. slow the reverse reaction only D. increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture. E. shift the equilibrium to the right.

d

The equilibrium constant for the reaction H2(g) + I2(g) ↔ 2HI (g) must be determined. If 1.00 g of HI is placed in a 2.00 L flask, which of the following is LEAST important in determining the equilibrium constant? A. The temperature must remain constant at the desired value B. Several measurements must be made to assure that the reaction is at equilibrium C. Only one of the three concentrations needs to be accurately determined D. All three concentrations must be accurately measured E. The original mass and volume of the flask must be accurately measured.

d

Of the following substances, an aqueous solution of __________ will form basic solutions. A) NaHS, Cu(NO3)2 B) KHCO3, NaHS C) NaF only D) NaF, E) NaHS, KHCO3 and NaF

e

The effect of temperature on a chemical system is best described using A. Ka and Q B. Kc C. Q and Le Chatelier's Principle D. Q E. Le Chatelier's Principle

e

The hydride ion, , is a stronger base than the hydroxide ion, . The product(s) of the reaction of hydride ion with water is/ are __________. A) H3O +1 B) OH- + H2 C) OH - +2H D) no reaction occurs E) H2O2

e

When an equal number of moles of each is mixed, which of these can be used to prepare a buffer solution? A. Cu(NH3)4 +2 B. KOH C. HCO3 -1 D.CO3 -2 E. SO3 -2

e