06 Reaction Rates & Equilibrium

which is the solubility product expression for PbCl2(s)

[pb2+]2[Cl-]2

The reversible reaction below produces ammonia. At equilibrium, a 1-L flask contains 0.15 mol H2, 0.25 mol N2, and 0.10 mol NH3. Calculate Keq for the reaction. N2(g)+3H2(g)←→2NH3(g)

12 *Keq = [NH3]^2/[N2][H2]^3 Keq = (0.1)^2/(0.25)(0.15)^3 Keq = 0.01/8.4x10^-4 Keq = 11.90

At equilibrium, a 1-L flask contains 0.15 mol H2, 0.25 mol N2, and 0.10 mol NH3. The substances react according to the equation below. What is the Keq for the reverse reaction? N2(g)+3H2(g)←→2NH3(g)

8.3 x 10^-2 *Keq = [N2][H2]^3 / [NH3]^2 Keq = (0.25)(0.15)^3 / (0.1)^2 Keq = 8.4x10^-4 / 0.01 Keq = 8.4 x 10 - 2 (The inverse for the forward reaction.)

Lead (II) sulfide (PbS) has a Ksp of 3.0 x 10^-28. What is the concentration of lead (II) ions in a saturated solution of PbS? A. 1.7 x 10^-14M B. 3.0 x 10^-14M C. 1.5 x 10^-14M

A. 1.7 x 10^-14M *Square roof of 3*10^-28

Why does a higher concentration make a reaction faster? A. There are more collisions per second. B. There are more collisions per second and the collisions are of greater energy. C. Collisions occur with greater energy.

A. There are more collisions per second.

Which variables are used to calculate the change in Gibbs free energy (ΔG)? A. change in enthalpy (ΔH), change in entropy (∆S), and temperature (T) B. change in enthalpy (ΔH), change in entropy (∆S), and the specific rate constant (k) C. change in enthalpy (ΔH), change in entropy (∆S) D. change in entropy (∆S) and temperature (T)

A. change in enthalpy (ΔH), change in entropy (∆S), and temperature (T)

An elementary reaction ____. A. converts reactants to products in a single step B. has only elements as reactants C. never needs a catalyst D. has only elements as products

A. converts reactants to products in a single step

The energy that is available to do work in a reaction is called _____. A. free energy B. heat C. enthalpy D. entropy

A. free energy

In a reaction, compounds A and B combine to form compounds C and D. The rate law is: rate= k[A][B]. What is the rate order? A. second-order B. first-order C. third-order D. k-order

A. second-order

An ionic solid is placed in water. Which information is described by the solubility product constant? A. the equilibrium between the solid and its ions in solution B. the temperature at which the solid and its ions reach equilibrium C. the amount of precipitate that will form from the ions

A. the equilibrium between the solid and its ions in solution

What information is NOT given by an overall equation for a chemical reaction? A. the reaction mechanism B. the relative numbers of molecules used C. the number of atoms participating in the reaction D. the probable order of the reaction

A. the reaction mechanism

The Ksp for silver chloride at 25*C is 1.8 x 10^-10. Which expression is equal to this value? A. [AgCl} - [AG+] x [Cl-] B. [Ag+] x [Cl-] C. [Ag+] + [Cl-] D [AgCl] / [Ag+] x [Cl-]

B. [Ag+] x [Cl-]

The ksp of AgCl is 1.8x10^-10. How do you know that mixing equal amounts of 0.04M solution of AgNO3 and 0.002M solution of NaCl will lead to the formation of a precipitate? A. (Ag+)x(Cl-)=Ksp AgCl B. (Ag+)x(Cl-)>Ksp AgCl C. (Ag+)x(Cl-)<Ksp AgCl

B. (Ag+)x(Cl-)>Ksp AgCl *.04*.002 = .00008 (This is greater than 1.8*1.8*10^-10)

Which one of the following systems has the highest entropy? A. 10 mL of water at 10*C B. 10 mL of water at 100*C C. 10 mL of water at 50*C

B. 10 mL of water at 100*C *entropy is directly proportional to the temperature of the substance and the no. of particles.therefore here 10ml of water at 100C has highest entropy.

The Ksp of copper sulfide (CuS) is 8.0 × 10^-37. What is the solubility concentration of [Cu2+] in a saturated solution at 25°C? A. 6.3 × 10-19M B. 8.9 × 10-19M C. 1.3 × 10-18M D. 6.4 × 10-73M

B. 8.9 × 10-19M *Square roof of 8 *10^-37

Why does adding sodium chloride to a saturated solution of lead chloride reduce the solubility of PbCl 2? A. Equilibrium is pushed toward the left in the equation NaCl (s) <--> Na+ (aq) + Cl- (aq) B. Equilibrium is pushed toward the left in the equation PbCl2 (s) <--> Pb^2+ (aq) + 2Cl- (aq) C. Equilibrium is pushed toward the right in the equation NaCl (s) <--> Na+ (aq) + Cl- (aq) D. Equilibrium is pushed toward the right in the equation PbCl2 (s) <--> Pb^2+ (aq) + 2Cl- (aq)

B. Equilibrium is pushed toward the left in the equation PbCl2 (s) <--> Pb^2+ (aq) + 2Cl- (aq)

Which is true about the numerical value of the Gibbs free-energy change for a spontaneous reaction? A. It is positive for temperatures above 850*C B. It is negative C. It indicates that work must be expended D. It is not related to enthalpy

B. It is negative

Chemicals A and B react according to the equation A + B --> C. How will the concentrations of each component of the reaction change over time? A. The concentrations of A, B, and C will increase. B. The concentrations of A and B will decrease, while C will increase. C. The concentrations of A and C will increase, while B will decrease. D. The concentrations of A, B, and C will decrease.

B. The concentrations of A and B will decrease, while C will increase.

In a first-order reaction, how does the rate change if the concentration of the reactant decreases to one-third its original value? A. The rate decreases by a factor of one-half. B. The rate decreases by a factor of one-third. C. The rate decreases by a factor of one-ninth. D. The rate increases by a factor of two-thirds.

B. The rate decreases by a factor of one-third.

Equilibrium is established between sodium chloride, NaCl, and its ions in solution according to this equation: NaCl(s)<---> Na+ (aq) + Cl-(aq) What will happen if concentrated HCL is added to the solution? A. Heat is released into the solution. B. The solubility of NaCl decreases. C. The concentrations of both Na+ and Cl- increase.

B. The solubility of NaCl decreases.

In a reaction progress curve, which point on the curve corresponds to an intermediate of the reaction? A. the top of a peak B. a valley between two peaks C. the point at the far right of the curve D. the point at the far left of the curve

B. a valley between two peaks

In a reaction, compounds A and B combine to form compounds C and D. Experimental data shows that the rate law is: rate = k[A][B]^3. What is the order of the reaction in A and B? A. second-order in A, second-order in B B. first-order in A, third-order in B C. fourth-order in A, fourth-order in B D. k-order in A, third-order in B

B. first-order in A, third-order in B

The magnitude of the specific rate constant (k) indicates____. A. the concentrations of reactants at the onset of a reaction. B. the rate that products form during a reaction. C. the concentrations of products when the reaction reaches equilibrium. D. the order of the reaction (such as first order or second order)

B. the rate that products form during a reaction.

If a system is left to change spontaneously, in what state will it end? A. the same state in which it began B. the state with the lowest possible energy consistent with the state of maximum disorder C. the state with the maximum disorder D. the state with the lowest possible energy

B. the state with the lowest possible energy consistent with the state of maximum disorder

Which describes the change in Gibbs free energy (ΔG) of a spontaneous reaction? A. ΔG = 0 B. ΔG < 0 C. ΔG > 0

B. ΔG < 0

The Ksp of zinc carbonate (ZnC03) is 1.0 x 10^10. What is the solubility concentration of carbonate ions in a standard solution at 25*C? A. 1.4 x 10^-5M B. 7.1 x 10^-6M C. 1.0 x 10^-5M D. 1.7 x 10^-5M

C. 1.0 x 10^-5M *Square root of 1.0*10^-10

What is the concentration of sulfide ion in a 1.0 L solution of iron (II) sulfide to which 0.04 mol of iron (II) nitrate is added? The Ksp of FeS is 8 x 10^-19. A. 5 x 10^-16M B. 1 x 10^-17M C. 2 x 10^-17M D. 3 X 10^-16M

C. 2 x 10^-17M Use the equation: Ksp=[Fe][S] then, equation simplifies to [S] = (8 x 10 ^19) / .04

What is the concentration of calcium ions in a saturated calcium carbonate solution at 25*C? (Ksp= 4.5 x 10^-9) A. 1.7 x 10^-3M B. 1.0 x 10^-9M C. 6.7 x 10^-5M D. 2.0 x 10^-17M

C. 6.7 x 10^-5M Use equation: Ksp= [Ca2+][CO3^2-]. b/c the concentrations of the 2 ions are equal to ea. other, solve by calculating the square root of the Ksp (4.5x10^-9)

Which statement is true? A. Entropy always increases in a spontaneous process. B. All spontaneous processes are exothermic. C. All spontaneous processes release free energy. D. All nonspontaneous processes are endothermic.

C. All spontaneous processes release free energy.

What does a low solubility product constant indicate about a compound? A. It conducts electricity in solution. B. It readily dissociates in water. C. It does not dissolve readily.

C. It does not dissolve readily.

For the reaction A-->B, the rate law is: rate= k x [A]. Over the course of 4 minutes, the concentration of A reduces by one-half from 1.00M to 0.50M. How is the rate affected? A. The rate reduces by a factor of 1/8. B. The rate reduces by a factor of 0.50k. C. The rate reduces by a factor of 1/2. D. The rate remains the same.

C. The rate reduces by a factor of 1/2.

Which is true about the combustion of carbon? A. Carbon is produced from oxygen and carbon dioxide B. Enthalpy remains constant C. The reaction is spontaneous D. Entropy decreases

C. The reaction is spontaneous

Which is the solubility product expression for Na3PO4 (s)? A. [Na]^+3 / [PO4]^3- B. [Na+3] / [PO4^3-] C. [Na+]^3 [PO4^3-] D. [Na]^+3 [PO4]^3-

C. [Na+]^3 [PO4^3-]

Spontaneous reactions _____. A. are always exothermic B. always take place at a rapid rate C. always release free energy D. always result in increased disorder of the system

C. always release free energy

A reaction is exothermic and involves an increase in entropy. Which describes the spontaneity of the reaction? A. never spontaneous B. spontaneous under certain conditions C. always spontaneous

C. always spontaneous

Which physical state of nitrogen has the highest entropy? A. solid B. liquid C. gas

C. gas

Which change in matter involves a decrease in entropy? A. crystals of sodium chloride (NaCl) dissolving in water B. wood and oxygen combining to produce gases, as in combustion C. gases combining into glucose, a solid compound, as in photosynthesis D. water being heated from 4*c to 94*c

C. gases combining into glucose, a solid compound, as in photosynthesis

The rate of a chemical reaction normally ____. A. decreases as temperature increases B. decreases as reactant concentration increases C. increases as reactant concentration increases D. is slowed down by a catalyst

C. increases as reactant concentration increases

In a reaction, compounds A and B combine to form compounds C and D. Experimental data shows that the reaction is third-order. Which rate law could describe this reaction? A. rate = k [A]^2 B. rate = k[A]^2 [B]^2 C. rate = k[A][B]^2 D. rate = k[A][B]^3

C. rate = k[A][B]^2

If a reaction is reversible, what are the relative amounts of reactant and product at the end of the reaction? A. no reactant; all product B. no product; all reactant C. some product; some reactant

C. some product; some reactant

A reversible reaction that produces a substantial amount of products at equilibrium and that releases free energy is described as ____. A. nonspontaneous in the forward direction B. nonspontaneous in both directions C. spontaneous in the forward direction D. spontaneous in both directions

C. spontaneous in the forward direction

Which variable is NOT required to calculate the Gibbs free-energy change for a chemical reaction? A. change in enthalpy B. temperature in kelvins C. temperature in *C D. change in entropy

C. temperature in *C

A saturated solution of Ag2CrO4 has a silver-ion concentration of 1.3 x 10^-4M. Which is the Ksp of Ag2CrO4? A. 3.9 x 10^-12 B. 1.3 x 10^-4 C. 6.5 x 10^-5 D. 1.1 x 10^-12

D. 1.1 x 10^-12 *since Ag2CrO4 --> 2 Ag+ & 1 CrO4)-2 the Ksp = [Ag+]^2 [CrO4)-2] Ksp = [1.3 * 10^-4M ]^2 [6.5 e-5] Ksp = [1.69 * 10^-8M ] [6.5 e-5] Ksp = 1.1 X 10^-12

According to collision theory, what must particles have in order to react when they collide? A. The individual particles must contain common atoms. B. The individual particles must have equal masses. C. The particles must be present in the same concentration. D. The particles must have sufficient kinetic energy.

D. The particles must have sufficient kinetic energy.

How are reactants converted to products in an elementary reaction? A. They are converted in multiple steps. B. They are converted without an activated complex. C. They are converted very quickly at a fast rate. D. They are converted in a single step.

D. They are converted in a single step.

Spontaneous reactions ____. A. always take place at a rapid rate B. are always exothermic C. always result in increased disorder of the system D. always release free energy

D. always release free energy

Entropy measures _____. A. heat transferred B. energy C. force D. disorder

D. disorder

Cellulose is the main component of wood. In a spontaneous reaction, cellulose combines with oxygen to form carbon dioxide and water. The reaction is described as spontaneous because it_____. A. occurs very rapidly and releases heat. B. changes a solid to one or more gases. C. occurs very gradually and runs to completion. D. favors the products and releases free energy.

D. favors the products and releases free energy.

For the reaction A-->B, the rate law is: rate= K x [A]. What is the order of the reaction? A. second-order B. k-order C. zero-order D. first-order

D. first-order

For a complex reaction, the reaction progress curve____. A. is a flat line B. shows energy versus pressure C. has only one peak D. has several hills and valleys

D. has several hills and valleys

Which group of compounds is described as insoluble? A. nitrates B. sulfates C. chlorides D. phosphates

D. phosphates

In an equilibrium reaction with a Keq of 1 x 10^8, the _____. A. reaction is spontaneous B. reaction is exothermic C. reactants are favored D. products are favored

D. products are favored *(B/c it is greater than 1. Less than one, the reactants are favored.)

What is the rate law for the following reaction? A + 2B --> C +D A. rate = k[A][B] B. rate = k[A]^2[B]^2 C. rate = k[A]^2[B] D. rate = k[A][B]^2

D. rate = k[A][B]^2

What is the order of this reaction? A+2B--> C+D A. zero B. second C. first D. third

D. third *(the overall order of a reaction is the sum of the exponents for the individual reactants. For this one, it's 1a + 2b = 3 so it's third.)

Another name for the activated complex is _____. A. rate limiter B. energy barrier C. collision group D. transition state

D. transition state

What happens to a catalyst in a reaction?

It is unchanged.

which equilibrium constant indicates a reaction in which the reactants are favored?

Keq= 0.04

Which expression represents a reaction rate?

Number / Time *Such as distance of race/ time to run.

Why does a catalyst cause a reaction to proceed faster?

The activation energy is lowered.

Which best demonstrates an example of the common ion effect

The compound CuCl is 500 times less soluble in sea water than it is in pure water.

According to La Chatelier's principle, what happens when a system in equilibrium is subjected to a change? *The reverse reaction is always favored to produce more reactants. *The forward reaction is favored to produce more products *The equilibrium shifts in the direction that relieves the stress on the system. *The equilibrium is unchanged by the stress.

The equilibrium shifts in the direction that relieves the stress on the system.

Why can grinding a solid into a fine powder increase the rate of reaction?

The powder has a greater surface area than the solid.

In an endothermic reaction at equilibrium, what is the effect of raising the temperature? *The reaction makes more products *The reaction makes more reactants *The reaction is unchanged

The reaction makes more products

What happens to a reaction at equilibrium when more reactant is added to the system? *The reaction makes more products *The reaction makes more reactants. *The reaction is unchanged.

The reaction makes more products

In a reaction (at equilibrium) that makes more moles of gas than it consumes, what is the effect of increasing the pressure? *The reaction makes more products. *The reaction is unchanged. *The reaction makes more reactants.

The reaction makes more reactants

Consider the reaction N2 (g) + 3H2 (g) <--> 2NH3 (g). What is the effect of decreasing the volume on the contained gases?

The reaction shifts toward the product gas.

Which occurs when the forward and reverse reactions occur at the same rate? *The changes are physical. *The system is in equilibrium. *The system is conserved. *The reactants and products are equal

The system is in equilibrium

The unstable arrangement of atoms that forms momentarily at the peak of the activation-energy barrier is known as the____.

activated complex

Activation energy is____.

an energy barrier between reactants and products

Which is the solubility product expression for CaF2(s)? a. [Ca^2+][F^2-] b. [Ca^2+][F-]^2 c. [Ca+][F]^2 d. [Ca^2+] / [F-]^2

b. [Ca^2+][F-]^2

Which describes the state at which products form at the same rate as reactants? *physical equilibrium *phase change *phase reversal *chemical equilibrium

chemical equilibrium

Which of the following substances act as catalysts in the body?

enzymes

Which of the changes listed below would shift this reaction to the right? 4HCl (g) + o2 (g) <-->2Cl2 (g) + 2H2O (g) *removal of O2 *addition of Cl2 *decrease of pressure *increase of pressure

increase of pressure

The rate of a chemical reaction normally___.

increases as reactant concentration increases

which factor increases the reaction rate by increasing particle speed?

increasing temp

What change will most likely increase the rate of a chemical reaction?

increasing the concentration of one of the reactants

A catalyst works by____.

lowering the activation energy barrier

The Keq of a reaction is 4 X 10^ -7. At equilibrium, the ____.? * products are favored *rate of the forward reaction is much greater than the rate of the reverse reaction *reactants are favored *reactants and products are present in equal amounts

reactants are favored

If a reaction has an equilibrium constant slightly greater than 1, what type of reaction is it? *reversible, favoring reactants *irreversible *reversible, favoring products *spontaneous

reversible, favoring products