24 Cards in this Set
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Which of the following statements correctly describes a reaction for which a plot of ln[A] versus time
produces a straight line?
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The rate constant is equal to the negative of the slope of the line
Since a plot of ln[A] vs. time is a straight line, the reaction is first-order. The first-order
integrated rate law that has the form of a straight line is: ln[A]t = −kt + ln[A]0. For a first-order
reaction, a plot o…
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For the reaction, X + Y → Z, the reaction rate is found to depend only upon the concentration of X. A plot of
1/[X] versus time gives a straight line. What is the rate law for this reaction?
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Rate = k[X]2.
Since a plot of 1/[X] vs. time is a straight line, the reaction is 2nd order. The reaction rate
only depends on the concentration of X and not Y, so the reaction must be second-order
with respect to X. The rate law must be: Rate = k[X]2.
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Which one of the following choices is the correct equilibrium constant expression for the reaction below?
Fe2O3 (s) + 3 H2 (g) ⇌ 2 Fe (s) + 3 H2O (g)
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Kc= (H2O)^3
_______
(H2)^3
The general form of the equilibrium constant expression (Kc) is the concentrations of
products raised to the power of the coefficients divided by the concentrations of reactants
raised to the power of the coefficients. Pure solids and pure liquids are not…
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At equilibrium, ________ .
[a] all chemical processes have ceased.
[b] the rate of the forward reaction equals the rate of the reverse reaction. *
[c] the equilibrium constant for the forward reaction equals the equilibrium constant of the reverse reaction.
[d] both (b) and (c) are…
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[b] the rate of the forward reaction equals the rate of the reverse reaction.
There are two common definitions of equilibrium: 1) The reactant and product
concentrations are no longer changing with time, and (2) The rate of the forward reaction
equals the rate of the reverse reactio…
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An aqueous equilibrium mixture of CoCl4^2−, CoBr4^2−, Cl−, and Br−
is present in a flask at 25°C. Which action
below will change the value of the equilibrium constant, K, from that which currently describes the concentration
relationships of the four species above?
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Put the flask into an 80°C water bath. *
The equilibrium constant for a given reaction is constant at a given temperature. Changing
the temperature will change the equilibrium constant [Choice (e)]. Changing the
concentration will lead to a new equilibrium position, but the same equ…
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The reaction,
A + B ⇌ X + Y
has Kc = 997 at 472 K. At equilibrium, ________________________ .
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Products Predominate
The value of the equilibrium constant is approximately 1000. Since the equilibrium
constant expression is the concentration of products divided by concentration of reactants,
this would indicate that the concentrations of products are roughly 1000 times greater
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For the following reactions occurring at 500 K, arrange them in order of increasing tendency to go to completion
(least → greatest tendency)
1) Kp = 1.7 × 10−2
2) Kp = 1.3 × 10−5
3) Kp = 5.9 × 10−5
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2<3<1
The larger the equilibrium constant, the more the reaction lies to the right (toward product
formation). Therefore, to arrange the three reactions from least to greatest tendency to go
to completion (toward product), we arrange them from the smallest K to the largest K
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Consider the following reaction at equilibrium.
2 CO2 (g) ⇌ 2 CO (g) + O2 (g) ∆H = −514 kJ
Increasing the temperature will _________________ ?
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Decrease the value of the equilibrium constant
The reaction is exothermic, so think of heat as a product. Increasing the temperature
increases the thermal energy (heat), so the system will shift to remove the added heat. The
system shifts left, decreasing the amount of product and in…
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In which of the following gas-phase equilibria is the yield of products increased by decreasing the volume of the
reaction vessel?
[a] CO(g) + H2O(g) ⇌ CO2(g) + H2(g)
[b] 2NO(g) + Cl2(g) ⇌ 2NOCl(g)
[c] 2SO3(g) ⇌ 2SO2(g) + O2(g)
[d] PCl5(g) ⇌ PCl3(g) + Cl2(g)
[e] The yield…
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(B)
If the volume of the container is decreased, the pressure inside the container increases. The
system will shift to decrease the pressure. The system can decrease the pressure by shifting
to the side of the equation with fewer moles of gas (P ∝ n). The only reaction that has fewer…
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Which of the following statements is/are correct about acids?
I. A Brønsted acid is a hydrogen-ion acceptor.
II. An Arrhenius acid increases the H3O+
concentration in an aqueous solution.
III. In an acidic solution, [H3O+] > 1.0 × 10−7 M at 25°C.
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II and III
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In the reaction,
HSO4^−(aq) + OH^-(aq) ⇌ SO4^2−(aq) + H2O(l)
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HSO4− and SO4
2−; H2O and OH−
A conjugate acid-base pair differs by one H+. The correct pairs are HSO4−/SO42− and
H2O/OH−. The acid part of the pair has one more H+ than the base part of the pair
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Which one of the following responses is true with regard to a 0.10 M solution of a weak acid, HA?
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pH > 1.00
The weak acid HA will ionize to H3O+ and A−
in a 1:1 mole ratio; hence [H3O+] = [A−
]. A
weak acid only partially ionizes, with a typical weak acid only ionizing about 1%. If a
0.10 M acid ionized completely (a strong acid), the hydronium concentration would equal
0.10 …
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For the reaction, X + Y → Z, the reaction rate is found to depend only upon the concentration of X. A plot of
ln[X] versus time gives a straight line. What is the rate law for this reaction?
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Rate = k[X]
Since a plot of ln[X] vs. time is a straight line, the reaction is first-order. The rate only
depends on X. The rate law is: Rate = k[X]
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Which of the following statements correctly describes a reaction for which a plot of 1/[A] versus time
produces a straight line?
[a] the rate constant for the reaction can be obtained from the value of the intercept on the y-axis.
[b] the rate of the reaction does not depend on the c…
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[d] the initial concentration of A can be calculated from the intercept on the y-axis.
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What is the equilibrium constant expression, Kc, for the reaction below?
4 CuO (s) + CH4 (g) ⇌ CO2 (g) + 4 Cu (s) + 2 H2O (g)
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Kc= (CO2)(H2O)^2
_________
(CH4)
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Consider the following equilibrium?
2 SO2 (g) + O2 (g) ⇌ 2 SO3 (g)
From which of the following starting conditions would it be impossible for this equilibrium to be achieved?
[a] 0.25 mol SO2(g) and 0.25 mol O2(g) in a 1.0 L container. [b] 0.75 mol SO2(g) in a 1.0 L container.
[…
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0.75 mol SO2(g) in a 1.0 L container
To reach equilibrium, we must start with reactants, or products, or a mixture of both. In choice
(b), we only have one of the reactants. There is no oxygen (O2) for SO2 to react with and
therefore it is not possible for the system to reach equilib…
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The reaction,
X + Y ⇌ 2 M
has Kc = 0.89 at 672 K. At equilibrium, ________________________ .
[a] products predominate substantially. [b] reactants predominate substantially.
[c] only products exist. [d] only reactants exist.
[e] roughly equal molar amounts of products and reactants a…
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Roughly equal molar amounts of products and reactants are present.
The value of the equilibrium constant is approximately 1. Since the equilibrium constant
expression is the concentration of products divided by concentration of reactants, this would
indicate that the concentrations o…
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Consider the following reaction at equilibrium.
2 CO2 (g) ⇌ 2 CO (g) + O2 (g)
Adding O2(g) to the container will _________________ ? The temperature remains constant.
[a] increase the concentration of CO(g) at equilibrium.
[b] decrease the concentration of CO2(g) at equilibrium.
[c] …
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Cause the reaction to shift to the left
The system will shift to remove some of the added O2(g) by shifting to the left.
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Of the following equilibria, only __________ will shift to the left in response to a decrease in the volume of the
container?
[a] H2(g) + Cl2(g) ⇌ 2HCl(g)
[b] 2SO3(g) ⇌ 2SO2(g) + O2(g)
[c] N2(g) + 3H2(g) ⇌ 2 NH3(g)
[d] 4 Fe (s) + 3O2(g) ⇌ 2Fe2O3(s)
[e] The yield of reactan…
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2SO3(g) ⇌ 2SO2(g) + O2(g)
If the volume of the container is decreased, the pressure inside the container increases. The
system will shift to decrease the pressure. The system can decrease the pressure by shifting to
the side of the equation with fewer moles of gas (P ∝ n). The only r…
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Which of the following statements is/are correct?
I. A Brønsted base is a hydrogen-ion acceptor.
II. An Arrhenius acid increases the OH−
concentration in an aqueous solution.
III. In a neutral, aqueous solution at 25°C, [H3O+] = 1.0 × 10−7 M.
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I and III
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The conjugate acid of HSO4- is
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H2SO4
A conjugate acid will have one more H+ than the base part of the pair.
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In an acidic solution, pH is _____ and pOH is _____.
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< 7, > 7
Because pH is the negative log of the hydronium concentration, if [H3O+] > 1.0 × 10−7 M
(acidic), the pH will be less than 7. If the pH is less than 7, the pOH will be greater than 7:
pH + pOH = 14 at 25°C
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Which of the following chemical equations corresponds to the base ionization constant, Kb, for nitrite ion
(NO2−)?
[a] HNO2(aq) + H2O(l) ⇌ NO2−
(aq) + H3O+(aq)
[b] NO2
−(aq) + H2O(l) ⇌ HNO2(aq) + OH−(aq)
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B
Nitrite as a base will accept an H+ from water producing its conjugate acid, HNO2, and
hydroxide, OH-
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Q > K...
Q <K....
Q = K
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Q > K, the system will shift to the left to achieve equilibrium
Q < K, the system will shift to the right to achieve equilibrium
Q = K, the system will be at equilibrium
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CHM 152: EXAM 2