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- A weak monoprotic acid is titrated with 0.100 M NaOH. It requires 50.0 mL of the NaOH solution to reach the equivalence point. After 25.0 mL of base is added, the pH of the solution is 3.62. Estimate the pKa of the weak acid.
Problem 93
- What is the pH of a solution made by mixing 0.30 mol NaOH, 0.25 mol Na2HPO4, and 0.20 mol H3PO4 with water and diluting to 1.00 L?
Problem 94
Problem 95
Suppose you want to do a physiological experiment that calls for a pH 6.50 buffer. You find that the organism with which you are working is not sensitive to the weak acid H2A 1Ka1 = 2 * 10-2; Ka2 = 5.0 * 10-72 or its sodium salts. You have available a 1.0 M solution of this acid and a 1.0 M solution of NaOH. How much of the NaOH solution should be added to 1.0 L of the acid to give a buffer at pH 6.50? (Ignore any volume change.)
- How many microliters of 1.000 M NaOH solution must be added to 25.00 mL of a 0.1000 M solution of lactic acid CH3CH(OH)COOH or HC3H5O3 to produce a buffer with pH = 3.75?
Problem 96
Problem 97d
Lead(II) carbonate, PbCO3, is one of the components of the passivating layer that forms inside lead pipes. (d) The EPA threshold for acceptable levels of lead ions in water is 15 ppb. Does a saturated solution of lead(II) carbonate produce a solution that exceeds the EPA limit?
Problem 98
For each pair of compounds, use Ksp values to determine which has the greater molar solubility: (a) CdS or CuS (b) PbCO3 or BaCrO4 (c) Ni(OH)2 or NiCO3 (d) AgI or Ag2SO4.
Problem 99b
The solubility of CaCO3 is pH dependent. (b) Use the Kb expression for the CO32- ion to determine the equilibrium constant for the reaction CaCO3(s) + H2O(l) ⇌ Ca2+(aq) + HCO3-(aq) + OH-(aq)
Problem 100a
Tooth enamel is composed of hydroxyapatite, whose simplest formula is Ca5(PO4)3OH, and whose corresponding 𝐾𝑠𝑝=6.8×10−27. As discussed in the “Chemistry and Life” box on “Tooth Decay and Fluoridation” in Section 17.5, fluoride in fluorinated water or in toothpaste reacts with hydroxyapatite to form fluoroapatite, Ca5(PO4)3F, whose 𝐾𝑠𝑝=1.0×10−60. a. Write the expression for the solubility-constant for hydroxyapatite and for fluoroapatite.
Problem 102
Calculate the solubility of Mg1OH22 in 0.50 M NH4Cl.
Problem 103
The solubility-product constant for barium permanganate, Ba1MnO422, is 2.5 * 10-10. Assume that solid Ba1MnO422 is in equilibrium with a solution of KMnO4. What concentration of KMnO4 is required to establish a concentration of 2.0 * 10-8 M for the Ba2 + ion in solution?
Problem 105
The solubility product constants of PbSO4 and SrSO4 are 6.3 * 10-7 and 3.2 * 10-7, respectively. What are the values of 3SO4 2 - 4, 3Pb2 + 4, and 3Sr2 + 4 in a solution at equilibrium with both substances?
- What pH is needed for a buffer to achieve a Mg2+ concentration of 3.0 × 10^-2 M in equilibrium with solid magnesium oxalate?
Problem 106
- The value of Ksp for Mg₃₁(AsO₄)₂₂ is 2.1 * 10⁻²⁰. The AsO₄³⁻ ion is derived from the weak acid H₃AsO₄ with pKa₁ = 2.22, pKa₂ = 6.98, pKa₃ = 11.502. (b) Calculate the pH of a saturated solution of Mg₃₁(AsO₄)₂₂ in water.
Problem 107
Problem 108
The solubility product for Zn1OH22 is 3.0 * 10-16. The formation constant for the hydroxo complex, Zn1OH242 - , is 4.6 * 1017. What concentration of OH- is required to dissolve 0.015 mol of Zn1OH22 in a liter of solution?
Problem 109a
The value of Ksp for Cd(OH)2 is 2.5 × 10-14. (a) What is the molar solubility of Cd(OH)2?
Problem 109b
The value of Ksp for Cd(OH)2 is 2.5 × 10–14. (b) The solubility of Cd(OH)2 can be increased through formation of the complex ion CdBr42- (Kf = 5 × 103). If solid Cd(OH)2 is added to a NaBr solution, what is the initial concentration of NaBr needed to increase the molar solubility of Cd(OH)2 to 1.0 × 10-3 mol/L?
Problem 110a
(a) Write the net ionic equation for the reaction that occurs when a solution of hydrochloric acid (HCl) is mixed with a solution of sodium formate 1NaCHO22.
- A sample of 7.5 L of NH3 gas at 22 _x001F_C and 735 torr is bubbled into a 0.50-L solution of 0.40 M HCl. Assuming that all the NH3 dissolves and that the volume of the solution remains 0.50 L, calculate the pH of the resulting solution.
Problem 111
Problem 112
What is the pH at 25 C of water saturated with CO2 at a partial pressure of 1.10 atm? The Henry's law constant for CO2 at 25 C is 3.1 * 10-2 mol>L@atm.
- Excess Ca(OH)₂ is shaken with water to produce a saturated solution. The solution is filtered, and a 50.00-mL sample is titrated with HCl, requiring 11.23 mL of 0.0983 M HCl to reach the endpoint. Calculate Ksp for Ca(OH)₂. Compare your result with that in Appendix D. Suggest a reason for any differences you find between your value and the one in Appendix D.
Problem 113
Problem 114
The osmotic pressure of a saturated solution of strontium sulfate at 25 C is 21 torr. What is the solubility product of this salt at 25 C?
Problem 115b,c
A concentration of 10–100 parts per billion (by mass) of Ag+ is an effective disinfectant in swimming pools. However, if the concentration exceeds this range, the Ag+ can cause adverse health effects. One way to maintain an appropriate concentration of Ag+ is to add a slightly soluble salt to the pool. Using Ksp values from Appendix D, calculate the equilibrium concentration of Ag+ in parts per billion that would exist in equilibrium with (b) AgBr (c) AgI.
Problem 116
Fluoridation of drinking water is employed in many places to aid in the prevention of tooth decay. Typically. the Fion concentration is adjusted to about 1 ppm. Some water supplies are also 'hard'; that is, they contain certain cations such as Ca2 + that interfere with the action of soap. Consider a case where the concentration of Ca2 + is 8 ppm. Could a precipitate of CaF2 form under these conditions? (Make any necessary approximations.)
Problem 117a
Baking soda (sodium bicarbonate, NaHCO3) reacts with acids in foods to form carbonic acid (H2CO3), which in turn decomposes to water and carbon dioxide gas. In a cake batter, the CO2(g) forms bubbles and causes the cake to rise. (a) A rule of thumb in baking is that 1/2 teaspoon of baking soda is neutralized by one cup of sour milk. The acid component in sour milk is lactic acid, CH3CH(OH)COOH. Write the chemical equation for this neutralization reaction.
Problem 117c
Baking soda (sodium bicarbonate, NaHCO3) reacts with acids in foods to form carbonic acid (H2CO3), which in turn decomposes to water and carbon dioxide gas. In a cake batter, the CO2(g) forms bubbles and causes the cake to rise. (c) If 1/2 teaspoon of baking soda is indeed completely neutralized by the lactic acid in sour milk, calculate the volume of carbon dioxide gas that would be produced at 1 atm pressure, in an oven set to 350 F.
Problem 118
In nonaqueous solvents, it is possible to react HF to create H2F+. Which of these statements follows from this observation? (a) HF can act like a strong acid in nonaqueous solvents, (b) HF can act like a base in nonaqueous solvents, (c) HF is thermodynamically unstable, (d) There is an acid in the nonaqueous medium that is a stronger acid than HF.