Consider the reaction: A sample of pure NH4HS is placed in a sealed 2.0-L container and

What are the two general concepts involved in equilibrium?

What is the rate of a chemical reaction? What is the difference between a chemical reaction with a fast rate and one with a slow rate?

Why do chemists seek to control reaction rates?

How do most chemical reactions occur?

What factors influence reaction rates? How?

What normally happens to the rate of the forward reaction as a reaction proceeds?

What is dynamic chemical equilibrium?

Explain how dynamic chemical equilibrium involves the concepts of sameness and constancy

Explain why the concentrations of reactants and products are not necessarily the same at equilibrium.

Devise your own analogylike the Narnia and Middle Earth analogy in the chapterto explain chemical equilibrium.

What is the equilibrium constant? Why is it significant?

Write the expression for the equilibrium constant for the following generic chemical equation. aA + bB cC + dD

What does a small equilibrium constant tell you about a reaction? A large equilibrium constant?

Why are solids and liquids omitted from the equilibrium expression?

Will the concentrations of reactants and products always be the same in every equilibrium mixture of a particular reaction at a given temperature? Explain.

What is Le Chteliers principle?

Apply Le Chteliers principle to your analogy from Question 12.

What is the effect of increasing the concentration of a reactant in a reaction mixture at equilibrium?

What is the effect of decreasing the concentration of a reactant in a reaction mixture at equilibrium?

What is the effect of increasing the concentration of a product in a reaction mixture at equilibrium?

What is the effect of decreasing the concentration of a product in a reaction mixture at equilibrium?

What is the effect of increasing the pressure of a reaction mixture at equilibrium if the reactant side has fewer moles of gas particles than the product side?

What is the effect of increasing the pressure of a reaction mixture at equilibrium if the product side has fewer moles of gas particles than the reactant side?

What is the effect of decreasing the pressure of a reaction mixture at equilibrium if the reactant side has fewer moles of gas particles than the product side?

What is the effect of decreasing the pressure of a reaction mixture at equilibrium if the product side has fewer moles of gas particles than the reactant side?

What is the effect of increasing the temperature of an endothermic reaction mixture at equilibrium? Of decreasing the temperature?

What is the effect of increasing the temperature of an exothermic reaction mixture at equilibrium? Of decreasing the temperature?

What is the solubility-product constant? What does it signify?

Write an expression for the solubility-product constant of AB2(s). Assume that an ion of B has a charge of (that is, ).

Write an expression for the solubility-product constant of A2B(s). Assume that an ion of B has charge of (that is, ).

What are solubility and molar solubility?

What is activation energy for a chemical reaction?

Explain why two reactants with a large Keq for a particular reaction might not react immediately when combined.

What is the effect of a catalyst on reaction? Why are catalysts so important to chemistry?

Does a catalyst affect the value of the equilibrium constant?

What are enzymes?

Two gaseous reactants are allowed to react in a 1-L flask, and the reaction rate is measured. The experiment is repeated with the same amount of each reactant and at the same temperature, but now in a 2-L flask (so the concentration of each reactant is now less). What is likely to happen to the measured reaction rate in the second experiment compared to the first?

The rate of phosphorus pentachloride decomposition is measured at a PCl5 pressure of 0.015 atm and then again at a PCl5 pressure of 0.30 atm. The temperature is identical in both measurements. Which rate is likely to be faster?

The body temperature of cold-blooded animals varies with the ambient temperature. From the point of view of reaction rates, explain why cold-blooded animals are more sluggish at cold temperatures.

The rate of a reaction doubles when the temperature increases from 25 C to 35 C. Explain why this is so.

The initial rate of a chemical reaction was measured, and one of the reactants was found to be reacting at a rate of 0.0011 mol/L s. The reaction was allowed to proceed for 15 minutes, and the rate was measured again. What would you predict about the second measured rate relative to the first?

When vinegar is added to a solution of sodium bicarbonate, the mixture immediately begins to bubble furiously. As time passes, however, the bubbling becomes less and less. Explain.

Write an equilibrium expression for each chemical equation. (a) (b) (c) (d) CH4 1g2 + 2 H2S1g2 CS2 1g2 + 4 H2 1g2 H2O1g2 + CO1g2 H2 1g2 + CO2 1g2 2 BrNO1g2 2 NO1g2 + Br2 1g2 2 NO2 1g2 N2O4 1g2

Write an equilibrium expression for each chemical equation. (a) (b) (c) (d) CO1g2 + Cl2 1g2 COCl2 1g2 SbCl5 1g2 SbCl3 1g2 + Cl2 1g2 N2 1g2 + O2 1g2 2 NO1g2 2 CO1g2 + O2 1g2 2 CO2 1g2

Write an equilibrium expression for each chemical equation involving one or more solid or liquid reactants or products. (a) (b) (c) (d) NH3 1aq2 + H2O1l2 NH4 +1aq2 + OH-1aq2 HF1aq2 + H2O1l2 H3O+1aq2 + F-1aq2 2 KClO3 1s2 2 KCl1s2 + 3 O2 1g2 PCl5 1g2 PCl3 1l2 + Cl2 1g2

Write an equilibrium expression for each chemical equation involving one or more solid or liquid reactants or products. (a) (b) (c) (d) C1s2 + CO2 1g2 2 CO1g2 2 C1s2 + O2 1g2 2 CO1g2 HCO3 -1aq2 + OH-1aq2 CO3 2-1aq2 + H2O1l2 H3O+1aq2 + CHO2 -1aq2 HCHO2 1aq2 + H2O1l2

Consider the reaction: Find the mistakes in the equilibrium expression and fix them. Keq = [H2][S2] [H2S] 2 H2S1g2 2 H2 1g2 + S2 1g2

Consider the reaction: Find the mistake in the equilibrium expression and fix it. Keq = [CO][Cl2] [COCl2] CO1g2 + Cl2 1g2 COCl2 1g2

For each equilibrium constant, indicate whether you would expect an equilibrium reaction mixture to be dominated by reactants, to be dominated by products, or to contain significant amounts of both. (a) (b) (c) (d) Keq = 0.47 Keq = 3.22 * 10-21 Keq = 1.24 Keq = 5.2 * 1017

For each equilibrium constant, indicate whether you would expect an equilibrium reaction mixture to be dominated by reactants, to be dominated by products, or to contain significant amounts of both. (a) (b) (c) (d) Keq = 4.7 * 10-9 Keq = 1.4 * 1019 Keq = 8.5 * 10-7 Keq = 0.75

Consider the reaction: An equilibrium mixture of this reaction at a certain temperature was found to have , , and . What is the value of the equilibrium constant at this temperature? [Cl2 [CO] = 0.105 M ] = 0.0844 M [COCl2] = 0.225 M COCl2 1g2 CO1g2 + Cl2 1g2

Consider the reaction: An equilibrium mixture of this reaction at a certain temperature was found to have , , and . What is the value of the equilibrium constant at this temperature? [H2] = 0.114 M [CH3OH] = 0.185 M [CO] = 0.105 M CO1g2 + 2 H2 1g2 CH3OH1g2

Consider the reaction: An equilibrium mixture of this reaction at a certain temperature was found to have , What is the value of the equilibrium constant at this temperature? [H2] = 2.74 * 10-2 M, and [S2] = 7.54 * 10-3 M. [H2S] = 0.562 M 2 H2S1g2 2 H2 1g2 + S2 1g2

Consider the reaction: An equilibrium mixture of this reaction at a certain temperature was found to have , , , and What is the value of the equilibrium constant at this temperature? 0.0274 M. [H2 [H2O] = 0.0115 M [CO2] = 0.175 M ] = [CO] = 0.0233 M CO1g2 + H2O1g2 CO2 1g2 + H2 1g2

Consider the reaction: An equilibrium mixture of this reaction at a certain temperature was found to have and What is the value of the equilibrium constant at this temperature? [H2S] = 0.355 M. [NH3] = 0.278 M NH4HS1s2 NH31g2 + H2S1g2

Consider the reaction: An equilibrium mixture of this reaction at a certain temperature was found to have What is the value of the equilibrium constant at this temperature? [CO2] = 0.548 M. CaCO31s2 CaO1s2 + CO21g2

An equilibrium mixture of the following reaction was found to have and at 248 C. What is the concentration of SbCl5? Keq = 4.9 * 10-4 at 248 C SbCl51g2 SbCl31g2 + Cl21g2 [SbCl3] = 0.0255 M [Cl2]= 0.135 M

An equilibrium mixture of the following reaction was found to have at 1200 C. What is the concentration of I? Keq = 1.1 * 10-2 at 1200 C I21g2 2 I1g2

An equilibrium mixture of the following reaction was found to have and at 25 C. What is the concentration of ICl? Keq = 81.9 at 25 C I21g2 + Cl21g2 2 ICl1g2

An equilibrium mixture of the following reaction was found to have and at 600 C. What is the concentration of SO2? Keq = 4.34 at 600 C N21g2 + 3 H21g2 2 NH31g2

Consider the reaction: Complete the table. Assume that all concentrations are equilibrium concentrations in moles per liter, M. N21g2 + 3 H21g2 2 NH31g2 T (K) [N2] [H2] [NH3] Keq 500 0.115 0.105 0.439 ______ 575 0.110 ______ 0.128 9.6 775 0.120 0.140 ______ 0.0584

Consider the reaction: Complete the table. Assume that all concentrations are equilibrium concentrations in moles per liter, M. H21g2 + I21g2 2 HI1g2 T (C) [H2] [I2] [HI] Keq 25 0.355 0.388 0.0922 ______ 340 ______ 0.0455 0.387 9.6 445 0.0485 0.0468 ______ 50.2

Consider this reaction at equilibrium. Predict the effect (shift right, shift left, or no effect) of (a) adding Cl2 to the reaction mixture. (b) adding COCl2 to the reaction mixture. (c) adding CO to the reaction mixture. CO1g2 + Cl21g2 COCl21g2

Consider this reaction at equilibrium. Predict the effect (shift right, shift left, or no effect) of (a) adding BrNO to the reaction mixture. (b) adding NO the reaction mixture. (c) adding Br2 to the reaction mixture. 2 BrNO1g2 2 NO1g2 + Br21g2

Consider this reaction at equilibrium. Predict the effect (shift right, shift left, or no effect) of (a) adding C to the reaction mixture. (b) condensing H2O and removing it from the reaction mixture. (c) adding CO to the reaction mixture. (d) removing H2 from the reaction mixture. C1s2 + H2O1g2 CO1g2 + H21g2

Consider this reaction at equilibrium. Predict the effect (shift right, shift left, or no effect) of (a) adding KCl to the reaction mixture. (b) adding KClO3 to the reaction mixture. (c) adding O2 to the reaction mixture. (d) removing O2 from the reaction mixture. 2 KClO31s2 2 KCl1s2 + 3 O21g2

Consider the effect of a volume change on this reaction at equilibrium. Predict the effect (shift right, shift left, or no effect) of (a) increasing the reaction volume. (b) decreasing the reaction volume. I2 1g2 2 I1g2

Consider the effect of a volume change on this reaction at equilibrium. Predict the effect (shift right, shift left, or no effect) of (a) increasing the reaction volume. (b) decreasing the reaction volume. 2 H2S1g2 2 H2 1g2 + S2 1g2

Consider the effect of a volume change on this reaction at equilibrium. Predict the effect (shift right, shift left, or no effect) of (a) increasing the reaction volume. (b) decreasing the reaction volume. I2 1g2 + Cl2 1g2 2 ICl1g2

Consider the effect of a volume change on this reaction at equilibrium. Predict the effect (shift right, shift left, or no effect) of (a) increasing the reaction volume. (b) decreasing the reaction volume. CO1g2 + H2O1g2 CO2 1g2 + H2 1g2

This reaction is endothermic. Predict the effect (shift right, shift left, or no effect) of (a) increasing the reaction temperature. (b) decreasing the reaction temperature. C1s2 + CO2 1g2 2 CO1g2

This reaction is endothermic. Predict the effect (shift right, shift left, or no effect) of (a) increasing the reaction temperature. (b) decreasing the reaction temperature. I2 1g2 2 I1g2

This reaction is exothermic. Predict the effect (shift right, shift left, or no effect) of (a) increasing the reaction temperature. (b) decreasing the reaction temperature. C6H12O6 1s2 + 6 O2 1g2 6 CO2 1g2 + 6 H2O1g2

The following reaction is exothermic. Predict the effect (shift right, shift left, or no effect) of (a) increasing the reaction temperature. (b) decreasing the reaction temperature. C2H4 1g2 + Br2 1g2 C2H4Br2 1g2

Coal, which is primarily carbon, can be converted to natural gas, primarily CH4, by the following exothermic reaction. If this reaction mixture is at equilibrium, predict the effect (shift right, shift left, or no effect) of (a) adding more C to the reaction mixture. (b) adding more H2 to the reaction mixture. (c) raising the temperature of the reaction mixture. (d) lowering the volume of the reaction mixture. (e) adding a catalyst to the reaction mixture. C1s2 + 2 H2 1g2 CH4 1g2

Coal can be used to generate hydrogen gas (a potential fuel) by this endothermic reaction. If this reaction mixture is at equilibrium, predict the effect (shift right, shift left, or no effect) of (a) adding more C to the reaction mixture. (b) adding more H2O(g) to the reaction mixture. (c) raising the temperature of the reaction mixture. (d) increasing the volume of the reaction mixture. (e) adding a catalyst to the reaction mixture. C1s2 + H2O1g2 CO1g2 + H2 1g2

For each compound, write an equation showing how the compound dissolves in water and write an expression for Ksp. (a) CaSO4 (b) AgCl (c) CuS (d) FeCO3

For each compound, write an equation showing how the compound dissolves in water and write an expression for Ksp. (a) Mg(OH)2 (b) FeCO3 (c) PbS (d) PbSO4

Determine what is wrong with the following Ksp expression for Fe(OH)2 and correct it. Ksp = [Fe2+][OH-]

Determine what is wrong with the following Ksp expression for Ba(OH)2 and correct it. Ksp = [Ba1OH22] [Ba2+][OH-] 2

A saturated solution of MgF2 has of Ksp for MgF2? 10 What is the value -4 M and [F-] = 5.2 * 10-4 M. [Mg2+] = 2.6 *

A saturated solution of AgI has and . What is the value of Ksp for AgI? [I-] = 9.2 * 10-9M [Ag+] = 9.2 * 10-9 M

A saturated solution of PbSO4 has . What is the concentration of ? SO4 2- 1.35 * 10-4 M [Pb2+] =

A saturated solution of PbCl2 has . What is the concentration of ? Pb2+ 2.86 * 10-2M [Cl-] =

Calculate the molar solubility of CaCO3.

Calculate the molar solubility of PbS.

Calculate the molar solubility of MgCO3.

Calculate the molar solubility of CuI 1.27 * 10 . -122

Complete the table. Assume that all concentrations are equilibrium concentrations in moles per liter, M. Compound [Cation] [Anion] Ksp SrCO3 2.4 * 10-5 2.4 * 10-5 ______ SrF2 1.0 * 10-3 ______ 4.0 * 10-9 Ag2CO3 ______ 1.3 * 10-4 8.8 * 10-12

Complete the table. Assume that all concentrations are equilibrium concentrations in moles per liter, M. Compound [Cation] [Anion] Ksp CdS 3.7 * 10-15 3.7 * 10-15 ______ BaF2 ______ 7.2 * 10-3 1.9 * 10-7 Ag2SO4 2.8 * 10-2 ______ 1.1 * 10-5

Consider the reaction: A solution is made containing initial and initial At equilibrium, the value of the equilibrium constant. Hint: Use the chemical reaction stoichiometry to calculate the equilibrium concentrations of and . SCN- Fe3+ [FeSCN Calculate 2+] = 1.7 * 10-4 . [SCN-] = 8.0 * 10-4 1.0 * 10 M. -3 M [Fe3+] = Fe3+1aq2 + SCN-1aq2 FeSCN2+1aq2

Consider the reaction: A solution is made containing initial . At equilibrium, . Calculate the value of the equilibrium constant. Hint: Use the chemical reaction stoichiometry to calculate the equilibrium concentrations of SO2Cl2 and SO2. [Cl2] = 1.2 * 10-2 0.020 M M [SO2Cl2] = SO2Cl2 1g2 SO2 1g2 + Cl2 1g2

Consider the reaction: A 3.67-L flask containing an equilibrium reaction mixture has and . How much HI in grams is in the equilibrium mixture? [I2 [H2] = 0.104 M ] = 0.0202 M Keq = 6.17 * 10-2 at 25 C CO1g2 + Cl21g2 COCl21g2

Consider the reaction: A 5.19-L flask containing an equilibrium reaction mixture has and . How much COCl2 in grams is in the equilibrium mixture? 7.3 * 10-7 M [Cl2 [CO] = 1.8 * 10 ] = -6 M Keq = 2.9 * 1010 at 25 C H21g2 + I21g2 2 HI1g2

This reaction is exothermic. If you were a chemist trying to maximize the amount of C2H4Cl2 produced, which of the following might you try? Assume that the reaction mixture reaches equilibrium. (a) increasing the reaction volume (b) removing C2H4Cl2 from the reaction mixture as it forms (c) lowering the reaction temperature (d) adding Cl2 C2H41g2 + Cl21g2 C2H4Cl21g2

This reaction is endothermic. If you were a chemist trying to maximize the amount of C2H4I2 produced, which of the following might you try? Assume that the reaction mixture reaches equilibrium. (a) decreasing the reaction volume (b) removing I2 from the reaction mixture (c) raising the reaction temperature (d) adding C2H4 to the reaction mixture C2H41g2 + I21g2 C2H4I21g2

Calculate the molar solubility of CuS. How many grams of CuS are present in 15.0 L of a saturated CuS solution?

Calculate the molar solubility of FeCO3. How many grams of FeCO3 are present in 15.0 L of a saturated FeCO3 solution?

A sample of tap water is found to be 0.025 M in . If 105 mg of Na2SO4 is added to 100.0 mL of the tap water, will any CaSO4 precipitate out of solution? Ca2+

If 50.0 mg of Na2CO3 are added to 150.0 mL of a solution that is in , will any MgCO3 precipitate from the solution?

The solubility of CaCrO4 at 25 C is 4.15 g/L. Calculate Ksp for CaCrO4.

The solubility of nickel(II) carbonate at 25 C is 0.042 g/L. Calculate Ksp for nickel(II) carbonate.

Consider the reaction: CaCO3 A sample of CaCO3 is placed into a sealed 0.500-L container and heated to 550 K at which the equilibrium constant is . When the reaction has come to equilibrium, what mass of solid CaO will be in the container? (Assume that the sample of CaCO3 was large enough that equilibrium could be achieved.) 4.1 * 10-4 CaO(s) + CO21g2

Consider the reaction: A sample of pure NH4HS is placed in a sealed 2.0-L container and heated to 550 K at which the equilibrium constant is . Once the reaction reaches equilibrium, what mass of NH3 is present in the container? (Assume that the sample of CaCO3 was large enough that equilibrium could be achieved.) 3.5 * 10-3 NH4HS1s2 NH31g2 + H2S1g2

A 2.55-L solution is 0.115 M in . If K2CO3 were added to the solution in order to precipitate the magnesium, what minimum mass of K2CO3 would be required to get a precipitate?

A 75.0-L solution is 0.0251 M in . If Na2SO4 were added to the solution in order to precipitate the calcium, what minimum mass of Na2SO4 would be required to get a precipitate?

H2 and I2 are combined in a flask and allowed to react according to the reaction: Examine the following figures (sequential in time) and determine which figure represents the point where equilibrium is reached. (a) (b) (c) (d) (e) (f) H21g2 + I21g2 2 HI1g2

Ethene (C2H4) can be halogenated by the reaction: where X2 can be Cl2, Br2, or I2. Examine the figures representing equilibrium concentrations of this reaction at the same temperature for the three different halogens. Rank the equilibrium constants for these three reactions from largest to smallest.

One of the main components of hard water is CaCO3. When hard water evaporates, some of the CaCO3 is left behind as a white mineral deposit. Plumbing fixtures in homes with hard water often acquire these deposits over time. Toilets, for example, may develop these deposits at the water line as the water in the toilet slowly evaporates away. If water is saturated with CaCO3, how much of it has to evaporate to deposit 0.250 g of CaCO3? Hint: Begin by using Ksp for CaCO3 to determine its solubility

Consider the following generic equilibrium in which a solid reactant is in equilibrium with a gaseous product: The following diagrams represent the reaction mixture at the following points: (a) initially; (b) after a short period of time has passed; and (c) at equilibrium. A(s) B(g) (a) (b) (c) A1s2 B1g2