Explain the statement that predictions about the direction of a reaction based on Gibbs

Consider the following equilibria in aqueous solution: (1) (2) (3) (a) Calculate the numerical value of the equilibrium constant for the reaction . (b) Calculate the concentration of AgCl(aq) in equilibrium with excess undissolved solid AgCl. (c) Find the numerical value of K for the reaction

Reaction 6-7 is allowed to come to equilibrium in a solution initially containing 0.010 0 M BrO 3, 0.010 0 M Cr3, and 1.00 M H. To find the concentrations at equilibrium, we can construct a table showing initial and final concentrations (see below). We use the stoichiometry coefficients of the reaction to say that if x mol of Br are created, then we must also make x mol of Cr2O7 2 and 8x mol of H. To produce x mol of Br, we must have consumed x mol of BrO 3 and 2x mol of Cr3. (a) Write the equilibrium constant expression that you would use to solve for x to find the concentrations at equilibrium. Do not try to solve the equation. (b) Because , we suppose that the reaction will go nearly to completion. That is, we expect both the concentration of Br and Cr2O7 2 to be close to 0.005 00 M at equilibrium. (Why?) That is, x 0.005 00 M. With this value of x, [H]  1.00 8x  1.04 M and [BrO 3 ]  0.010 0 x  0.005 0 M. However, we cannot say [Cr3]  0.010 0 2x  0, because there must be some small concentration of Cr3 at equilibrium. Write [Cr3] for the concentration of Cr3and solve for [Cr3]. The limiting reagent in this example is Cr3. The reaction uses up Cr3 before consuming BrO 3 . K  1 1011 AgCl(s)

Find [La3] in the solution when excess solid lanthanum iodate, La(IO3)3, is stirred with 0.050 M LiIO3 until the system reaches equilibrium. Assume that IO 3 from La(IO3)3 is negligible compared with IO 3 from LiIO3. 6-

Which will be more soluble (moles of metal dissolved per liter of solution), \(\mathrm{Ba}\left(\mathrm{IO}_3\right)_2\ \left(K_{\mathrm{sp}}=1.5\times10^{-9}\right)\) or \(\mathrm{Ca}\left(\mathrm{IO}_{3}\right)_{2} \ \left (K_{\mathrm{sp}}=\right.\left.7.1 \times 10^{-7}\right)\)? Give an example of a chemical reaction that might occur that would reverse the predicted solubilities.

Fe(III) precipitates from acidic solution by addition of OH to form Fe(OH)3(s). At what concentration of OH will [Fe(III)] be reduced to 1.0 1010 M? If Fe(II) is used instead, what concentration of OH will reduce [Fe(II)] to 1.0 1010 M? 6-F.

Is it possible to precipitate 99.0% of 0.010 M Ce3 by adding oxalate (C2O4 2) without precipitating 0.010 M Ca2? 6-G

For a solution of Ni2 and ethylenediamine, the following equilibrium constants apply at 20C: Ethylenediamine (abbreviated en) Calculate the concentration of free Ni2 in a solution prepared by mixing 0.100 mol of en plus 1.00 mL of 0.010 0 M Ni2 and diluting to 1.00 L with dilute base (which keeps all the en in its unprotonated form. Assume that nearly all nickel is in the form Ni(en)3 2, so [Ni(en)3 2]  1.00 105 M. Calculate the concentrations of Ni(en)2 and Ni(en)2 2 to verify that they are negligible in comparison with Ni(en)3 2. Ni(en) l

If each compound is dissolved in water, will the solution be acidic, basic, or neutral? (a) NaBr (e) (CH3)4NCl (b) NaCH3CO 2 (f) (c) NH 4Cl (g) Fe(NO3)3 (d) K3PO4 6-I. S

Succinic acid dissociates in two steps: Calculate Kb1 and Kb2 for the following reactions: HOCCH2CH2COH OH O O HOCCH2CH2CO H2OT O O Kb2 HOCCH2CH2CO OH O O OCCH2CH2CO H2OT O O Kb1 HOCCH2CH2COTOCCH2CH2CO H K2  2.3 106 O O O O K2 HOCCH2CH2COHTHOCCH2CH2CO H K1  6.2 105 O O O

Histidine is a triprotic amino acid:

(a) From Kw in Table 6-1, calculate the pH of pure water at 0, 20, and 40C. (b) For the reaction D2O D OD, K  [D][OD]  1.35 1015 at 25C. In this equation, D stands for deuterium, which is the isotope 2 H. What is the pD ( log[D]) for neutral D2O?

To evaluate the equilibrium constant in Equation 6-2, we must express concentrations of solutes in mol/L, gases in bars, and omit solids, liquids, and solvents. Explain why.

Why do we say that the equilibrium constant for the reaction (or any other reaction) is dimensionless?

Explain the statement that predictions about the direction of a reaction based on Gibbs free energy or Le Chteliers principle are thermodynamic, not kinetic.

Write the expression for the equilibrium constant for each of the following reactions. Write the pressure of a gaseous molecule, X, as PX.

For the reaction , the concentrations at equilibrium are found to be A: 2.8 103 Pa C: 12.8 M E: 3.6 104 Torr B: 1.2 102 M D: 16.5 M Find the numerical value of the equilibrium constant that would appear in a conventional table of equilibrium constants.

From the equations find the value of K for the reaction HOBr H . OBr HOCl OBr HOBr OCl K  15 K  3.0 108 HOCl H OCl 2A(g) B(a

(a) A favorable entropy change occurs when S is positive. Does the order of the system increase or decrease when S is positive? (b) A favorable enthalpy change occurs when H is negative. Does the system absorb heat or give off heat when H is negative? (c) Write the relation between G, H, and S. Use the results of parts (a) and (b) to state whether G must be positive or negative for a spontaneous change.

For the reaction , G59.0 kJ/mol at 298.15 K. Find the value of K for the reaction.

The formation of tetrafluoroethylene from its elements is highly exothermic: Fluorine Graphite Tetrafluoroethylene (a) If a mixture of F2, graphite, and C2F4 is at equilibrium in a closed container, will the reaction go to the right or to the left if F2 is added? (b) Rare bacteria from the planet Teflon eat C2F4 and make Teflon for their cell walls. Will the reaction go to the right or to the left if these bacteria are added? (c) Will the reaction go right or left if solid graphite is added? (Neglect any effect of increased pressure due to the decreased volume in the vessel when solid is added.)

BaCl2H2O(s) loses water when it is heated in an oven: H  63.11 kJ/mol at 25C S148 J/(K mol) at 25C (a) Write the equilibrium constant for this reaction. Calculate the vapor pressure of gaseous H2O above BaCl2H2O at 298 K. (b) If H and S are not temperature dependent (a poor assumption), estimate the temperature at which above BaCl2 H2O(s) will be 1 bar. 6-

The equilibrium constant for the reaction of is Kb  1.479 105 at 5C and 1.570 105 at 10C. (a) Assuming H and S are constant in the interval 510C (probably a good assumption for small T ), use Equation 6-8 to find H for the reaction in this temperature range. (b) Describe how Equation 6-8 could be used to make a linear graph to determine H, if H and S were constant over some temperature range. 6

For K  7.2 104 at 1 362 K and H is positive. A vessel is charged with 48.0 Pa HBr, 1 370 Pa H2, and 3 310 Pa Br2 at 1 362 K. (a) Will the reaction proceed to the left or the right to reach equilibrium? (b) Calculate the pressure (in pascals) of each species in the vessel at equilibrium. (c) If the mixture at equilibrium is compressed to half of its original volume, will the reaction proceed to the left or the right to reestablish equilibrium? (d) If the mixture at equilibrium is heated from 1 362 to 1 407 K, will HBr be formed or consumed in order to reestablish equilibrium?

Henrys law states that the concentration of a gas dissolved in a liquid is proportional to the pressure of the gas. This law is a consequence of the equilibrium where Kh is called the Henrys law constant. (The same law applies to other solvents, but the value of Kh is different for each solvent.) For the gasoline additive MTBE, Kh  1.71 M/bar. Suppose we have a closed container with aqueous solution and air in equilibrium. If the concentration of MTBE in the water is 1.00 102 ppm ( 100 g MTBE/g solution 100 g/mL), what is the pressure of MTBE in the air? Methyl-t-butylether (MTBE, FM 88.15)

Find the concentration of Cu in equilibrium with CuBr(s) and 0.10 M Br. 6-

What concentration of Fe(CN)6 4 (ferrocyanide) is in equilibrium with 1.0 M Ag and Ag4Fe(CN)6(s). Express your answer with a prefix from Table 1-3. C

Find [Cu2] in a solution saturated with Cu4(OH)6(SO4) if [OH] is fixed at 1.0 106 M. Note that Cu4(OH)6(SO4) gives 1 mol of SO4 2 for 4 mol of Cu2. 6-1

(a) From the solubility product of zinc ferrocyanide, Zn2Fe(CN)6, calculate the concentration of Fe(CN)6 4 in 0.10 mM ZnSO4 saturated with Zn2Fe(CN)6. Assume that Zn2Fe(CN)6 is a negligible source of Zn2. (b) What concentration of K4Fe(CN)6 should be in a suspension of solid Zn2Fe(CN)6 in water to give [Zn2]  5.0 107 M? 6-1

Solubility products predict that cation A3 can be 99.999% separated from cation B2 by precipitation with anion X. When the separation is tried, we find 0.2% contamination of AX3(s) with B2. Explain what might be happening. 6-

A solution contains 0.050 0 M Ca2 and 0.030 0 M Ag. Can 99% of Ca2 be precipitated by sulfate without precipitating Ag? What will be the concentration of Ca2 when Ag2SO4 begins to precipitate? 6-20

A solution contains 0.010 M Ba2 and 0.010 M Ag. Can 99.90% of either ion be precipitated by chromate (CrO4 2) without precipitating the other metal ion? 6-

If a solution containing 0.10 M Cl, Br, I, and CrO4 2 is treated with Ag, in what order will the anions precipitate? Comp

?Explain why the total solubility of lead in Figure 6-3 first decreases and then increases as \([ \text{I}^- ]\) increases. Give an example of the chemistry in each of the two domains. Figure 6-3 Total solubility of lead(II) (curve with circles) and solubilities of individual species (straight lines) as a function of the concentration of free iodide. To the left of the minimum, \([ \text{Pb} ]_{\text{total}}\) is governed by the solubility product for PbI\textsubscript{2}(s). As \([ \text{I}^- ]\) increases, \([ \text{Pb} ]_{\text{total}}\) decreases because of the common ion effect. At high values of \([ \text{I}^- ]\), PbI\textsubscript{2}(s) redissolves because it reacts with \(\text{I}^-\) to form soluble complex ions, such as \(\text{PbI}_4^{2-}\). Note logarithmic scales. The solution is made slightly acidic so that \([\text{PbOH}^+]\) is negligible.

Identify the Lewis acids in the following reactions:

The cumulative formation constant for SnCl2(aq) in 1.0 M NaNO3 is 2  12. Find the concentration of SnCl2(aq) for a solution in which the concentrations of Sn2 and Cl are both somehow fixed at 0.20 M. 6

Given the following equilibria, calculate the concentration of each zinc species in a solution saturated with Zn(OH)2(s) and containing [OH] at a fixed concentration of 3.2 107 M. Zn(OH)2(s) Ksp  3 1016 Zn(OH) 1  1 104 Zn(OH)2(aq) 2  2 1010 Zn(OH) 3 3  8 1013 Zn(OH)4 2 4  3 1015 6-26.

Although KOH, RbOH, and CsOH have little association between metal and hydroxide in aqueous solution, Li and Na do form complexes with OH: Prepare a table like the one in Exercise 6-B showing initial and final concentrations of Na, OH, and NaOH(aq) in 1 F NaOH Na K

In Figure 6-3, the concentration of PbI2(aq) is independent of [I]. Use any of the equilibrium constants for Reactions 6-11 through 6-15 to find the equilibrium constant for the reaction , which is equal to the concentration of PbI2(aq).

Distinguish Lewis acids and bases from Brnsted-Lowry acids and bases. Give an example of each.

Fill in the blanks: (a) The product of a reaction between a Lewis acid and a Lewis base is called ________. (b) The bond between a Lewis acid and a Lewis base is called ________ or _______. (c) Brnsted-Lowry acids and bases related by gain or loss of one proton are said to be ________. (d) A solution is acidic if _______. A solution is basic if _______.

Why is the pH of distilled water usually 7? How can you prevent this from happening?

Gaseous SO2 is created by combustion of sulfur-containing fuels, especially coal. Explain how SO2 in the atmosphere makes acidic rain.

Use electron dot structures to show why tetramethylammonium hydroxide, (CH3)4NOH, is an ionic compound. That is, show why hydroxide is not covalently bound to the rest of the molecule. 6

Identify the Brnsted-Lowry acids among the reactants in the following reactions:

Write the autoprotolysis reaction of H2SO4.

Identify the conjugate acid-base pairs in the following reactions: (a) (b) pH

Calculate [H] and pH for the following solutions: (a) 0.010 M HNO3 (d) 3.0 M HCl (b) 0.035 M KOH (e) 0.010 M [(CH3)4N]OH (c) 0.030 M HCl Tetramethylammonium hydroxide 6-

Use Table 6-1 to calculate the pH of pure water at (a) 25C and (b) 100C.

The equilibrium constant for the reaction is 1.0 1014 at 25C. What is the value of K for the reaction ? 6

An acidic solution containing 0.010 M La3 is treated with NaOH until La(OH)3 precipitates. At what pH does this occur?

Use Le Chteliers principle and Kw in Table 6-1 to decide whether the autoprotolysis of water is endothermic or exothermic at (a) 25C; (b) 100C; (c) 300C.

Make a list of the common strong acids and strong bases. Memorize this list.

Write the formulas and names for three classes of weak acids and two classes of weak bases.

Write the Ka reaction for trichloroacetic acid, Cl3CCO2H, for anilinium ion, , and for lanthanum ion, La3.

Write the Kb reactions for pyridine and for sodium 2-mercaptoethanol.

Write the Ka and Kb reactions of NaHCO3.

Write the stepwise acid-base reactions for the following ions in water. Write the correct symbol (for example, Kb1) for the equilibrium constant for each reaction. (a) (b)

Which is a stronger acid, (a) or (b)? (a) (b) Which is a stronger base, (c) or (d)? (c) (d)

Write the Kb reaction of CN. Given that the Ka value for HCN is 6.2 1010, calculate Kb for CN. 6-

Write the Ka2 reaction of phosphoric acid (H3PO4) and the Kb2 reaction of disodium oxalate (Na2C2O4).

From the Kb values for phosphate in Equations 6-32 through 6-34, calculate the three Ka values of phosphoric acid.

From the following equilibrium constants, calculate the equilibrium constant for the reaction .

(a) Using only Ksp from Table 6-3, calculate how many moles of Ca(OH)2 will dissolve in 1.00 L of water. (b) How will the solubility calculated in part (a) be affected by the K1 reaction in Table 6-3?

(a) Using only Ksp from Table 6-3, calculate how many moles of Ca(OH)2 will dissolve in 1.00 L of water. (b) How will the solubility calculated in part (a) be affected by the K1 reaction in Table 6-3?