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American Chemical Society General Chemistry Acids and Solubility

pH, buffers, titrations, and solubility equilibrium.

These questions are original. This is not an official American Chemical Society exam, and FreeExam is not affiliated with the American Chemical Society.

  1. 1.A stock bottle of hydrochloric acid is labeled 1.0 × 10^(−3) M. The acid is fully dissociated at 25°C. What is the pH?

  2. 2.A sodium hydroxide solution has [OH−] = 1.0 × 10^(−2) M at 25°C. What is the pH?

  3. 3.Nitric acid is prepared at 1.0 × 10^(−4) M. It is a strong acid at 25°C. What is the pOH?

  4. 4.Find the pH of 1.0 × 10^(−5) M potassium hydroxide at 25°C.

  5. 5.Which aqueous solution has pH 2 at 25°C?

  6. 6.Lithium hydroxide is dissolved to 1.0 × 10^(−3) M and kept at 25°C. What is the pOH?

  7. 7.Perchloric acid is fully dissociated, and [H3O+] = 1.0 × 10^(−4) M at 25°C. What is the pH?

  8. 8.Barium hydroxide is 5.0 × 10^(−3) M at 25°C. Each formula unit releases two hydroxide ions. What is the pH?

  9. 9.A cleaning solution is 1.0 × 10^(−1) M sodium hydroxide at 25°C. What is the pH?

  10. 10.Acid HA has Ka = 1.0 × 10^(−4). Acid HB has Ka = 1.0 × 10^(−6). Which comparison is right?

  11. 11.Acid HX has pKa = 3. Acid HY has pKa = 5. Which acid is stronger?

  12. 12.At equilibrium, [H3O+] = 1.0 × 10^(−3) M, [A−] = 1.0 × 10^(−3) M, and [HA] = 1.0 × 10^(−2) M. What is Ka of HA?

  13. 13.A weak acid has Ka = 1.0 × 10^(−5). What is its pKa?

  14. 14.Acid HM has pKa = 4. Acid HN has pKa = 2. Which acid is stronger?

  15. 15.Acids P and Q start at the same concentration. Ka of P is 1.0 × 10^(−3) and Ka of Q is 1.0 × 10^(−7). Which solution has the lower pH?

  16. 16.Equilibrium values are [H3O+] = 2.0 × 10^(−3) M, [B−] = 2.0 × 10^(−3) M, and [HB] = 4.0 × 10^(−2) M. What is Ka?

  17. 17.Acid R has Ka = 1.0 × 10^(−8). Acid S has Ka = 1.0 × 10^(−2). Which acid is weaker?

  18. 18.Acid HT has pKa = 6. Acid HU has Ka = 1.0 × 10^(−4). Which acid is stronger?

  19. 19.A buffer has acid pKa = 5 and [A−]/[HA] = 10. What is the pH?

  20. 20.A buffer has pKa = 7 and [A−]/[HA] = 0.10. What is the pH?

  21. 21.A buffer is at pH 4. The weak acid has pKa 5. What is [A−]/[HA]?

  22. 22.A conjugate pair has pKa = 9. The beaker contains 0.20 M A− and 0.020 M HA. What is the pH?

  23. 23.A student mixes a buffer with 0.030 M HA and 0.30 M A−. The pKa is 4. What is the pH?

  24. 24.In an acetate buffer, pKa = 5 and [HA] = 10[A−]. What is the pH?

  25. 25.A buffer reads pH 8. The acid pKa is 7. What is [A−]/[HA]?

  26. 26.Equal volumes of 0.10 M HA and 1.0 M A− are combined. The pKa is 6. What is the pH of the mixture?

  27. 27.A buffer is 1.0 M in HA and 0.10 M in A−. The pKa is 3. What is the pH?

  28. 28.1.0 × 10^(−3) mol of HCl is added to 1.00 L of pure water and to 1.00 L of a pKa 5 buffer that starts at 0.47 M A− and 0.047 M HA. The new log([A−]/[HA]) is 0.990. At 25°C, which pH drop is larger?

  29. 29.1.0 × 10^(−2) mol of HNO3 is dissolved in 1.00 L of pure water at 25°C. The same amount is added to a buffer. What is the new pH of the water?

  30. 30.A pKa 6 buffer starts at 0.20 M A− and 0.020 M HA. Adding 1.0 × 10^(−3) mol HCl to 1.00 L changes log([A−]/[HA]) to 0.977. The same addition is made to pure water. What is the new buffer pH?

  31. 31.1.0 × 10^(−2) mol HCl is added to 1.00 L of a pKa 4 buffer that starts at 1.00 M A− and 0.10 M HA. The new log([A−]/[HA]) is 0.954. By how much does the buffer pH fall?

  32. 32.1.0 × 10^(−4) mol HCl is added to 1.00 L of pure water at 25°C, and the same amount is added to a buffer. What happens to the water?

  33. 33.Adding 1.0 × 10^(−3) mol HCl to 1.00 L of pure water is compared with the same addition to 1.00 L of a pKa 9 buffer (0.80 M A− and 0.080 M HA). The new log([A−]/[HA]) is 0.994. Which pH change is smaller?

  34. 34.A pKa 5 buffer contains 0.30 M A− and 0.030 M HA. After 1.0 × 10^(−2) mol HCl is added to 1.00 L, log([A−]/[HA]) is 0.860. The same acid in pure water gives pH 2. What is the final buffer pH?

  35. 35.A lab adds 1.0 × 10^(−5) mol of strong acid to 1.00 L of pure water at 25°C and the same amount to 1.00 L of buffer. What is the new pH of the water?

  36. 36.1.0 × 10^(−4) mol HCl is added to 1.00 L of pure water and to 1.00 L of a pKa 8 buffer that starts at 0.50 M A− and 0.050 M HA. The new log([A−]/[HA]) is 0.999. How do the pH drops compare?

  37. 37.20.0 mL of 0.10 M HCl is titrated with 0.10 M NaOH at 25°C. What volume of NaOH reaches equivalence, and what is the pH there?

  38. 38.10.0 mL of 0.30 M HNO3 is titrated with 0.20 M KOH at 25°C. What volume of KOH reaches pH 7?

  39. 39.At 25°C, 25.0 mL of 0.10 M HBr is titrated with 0.25 M NaOH. What volume of NaOH reaches equivalence?

  40. 40.A titration of HCl with NaOH reaches the equivalence point at 25°C. What is the pH there?

  41. 41.50.0 mL of 0.10 M HI is titrated with 0.20 M LiOH at 25°C. Which added volume is the equivalence point?

  42. 42.15.0 mL of 0.40 M HClO4 is titrated with 0.20 M NaOH at 25°C. How many milliliters of NaOH reach equivalence?

  43. 43.50.0 mL of 0.20 M NaOH is titrated with 0.25 M HCl at 25°C. What volume of HCl reaches pH 7?

  44. 44.30.0 mL of 0.10 M KOH is titrated with 0.10 M HNO3 at 25°C. At equivalence, which pair is correct?

  45. 45.36.0 mL of 0.25 M HCl is titrated with 0.15 M NaOH at 25°C. What NaOH volume reaches equivalence?

  46. 46.A weak acid with pKa 5 is titrated with NaOH at 25°C. Halfway to equivalence, what is the pH?

  47. 47.Acetic acid, a weak acid, is titrated with KOH. At the equivalence point at 25°C, where is the pH?

  48. 48.20.0 mL of 0.10 M weak acid HA is titrated with 0.10 M NaOH. The pKa is 4. What is the pH after 10.0 mL of NaOH is added?

  49. 49.A weak acid of pKa 6 needs 40.0 mL of strong base to reach equivalence. After 20.0 mL of that base, what is the pH?

  50. 50.HA has pKa 8 and is titrated with LiOH at 25°C. Which statement matches the halfway point and the equivalence point?

  51. 51.30.0 mL of 0.20 M HA, pKa 5, is titrated with 0.20 M NaOH at 25°C. What is the pH after 15.0 mL of NaOH?

  52. 52.At equivalence in a titration of a weak acid with NaOH at 25°C, the flask contains the salt NaA. What is true of the pH?

  53. 53.Weak acid HB, pKa 3, is titrated with KOH. Equivalence takes 24.0 mL of KOH. What is the pH after 12.0 mL of KOH?

  54. 54.A weak acid of pKa 7 is titrated with NaOH at 25°C. Halfway to equivalence the pH is 7. What is the pH at equivalence?

  55. 55.A titration has an equivalence pH near 7. Methyl orange changes near pH 4, bromothymol blue near pH 7, phenolphthalein near pH 9, and alizarin yellow near pH 11. Which indicator fits best?

  56. 56.Equivalence in this weak-acid titration is near pH 9. Four indicators change color near pH 4, pH 5, pH 7, and pH 9. Which color-change pH should be chosen?

  57. 57.A strong-acid strong-base titration at 25°C has equivalence at pH 7. Indicators change near 3, 5, 7, and 10. Which change is nearest that pH?

  58. 58.Equivalence is near pH 5 for a weak base titrated with a strong acid. Indicators change near pH 3, 5, 8, and 10. Which is the best choice?

  59. 59.Phenolphthalein changes near pH 9, methyl red near pH 5, bromothymol blue near pH 7, and thymol blue (acid range) near pH 2. Equivalence is about pH 9. Which indicator should be used?

  60. 60.Equivalence pH is about 4. Indicator color changes are centered near 4, 7, 9, and 11. Which center belongs with this titration?

  61. 61.A titration ends near pH 8. One indicator changes from 7.5 to 8.5, another from 3 to 4, another from 5 to 6, and another from 10 to 12. Which range contains the equivalence pH?

  62. 62.Equivalence is at pH 10. Indicators are listed by the center of the color change: 4, 6, 8, and 10. Which center should be selected?

  63. 63.Strong acid titrated with strong base reaches equivalence at pH 7 at 25°C. Indicators on the shelf change near pH 5, 7, 9, and 11. Which should be used?

  64. 64.For this problem, the 1:1 salt AgCl has Ksp = 1.0 × 10^(−10) at 25°C. What is its molar solubility in pure water?

  65. 65.CaCO3 is a 1:1 salt. Use Ksp = 4.0 × 10^(−8) for this problem. What is the molar solubility in pure water?

  66. 66.A 1:1 salt has molar solubility 3.0 × 10^(−5) M in pure water. What is Ksp?

  67. 67.PbSO4 dissolves as Pb2+ and SO4^2− in a 1:1 ratio. Use Ksp = 1.0 × 10^(−8). What is the molar solubility?

  68. 68.SrSO4 is a 1:1 salt. Use Ksp = 9.0 × 10^(−8) for this problem. What is the molar solubility in pure water?

  69. 69.The molar solubility of a 1:1 salt in pure water is 2.0 × 10^(−3) M. What is Ksp?

  70. 70.AgBr is a 1:1 salt. Use Ksp = 1.0 × 10^(−12) for this problem. What is the molar solubility in pure water?

  71. 71.A 1:1 salt dissolves to 1.0 × 10^(−3) M in pure water. What is Ksp?

  72. 72.A 1:1 salt has Ksp = 4.0 × 10^(−10). What is the molar solubility in pure water?

  73. 73.AgCl has Ksp = 1.0 × 10^(−10). What is its molar solubility in 0.10 M NaCl, where chloride is already present?

  74. 74.CaCO3 has Ksp = 4.0 × 10^(−8). In which solution is its molar solubility smallest?

  75. 75.PbSO4 has Ksp = 1.0 × 10^(−8). Estimate its molar solubility in 1.0 × 10^(−2) M Na2SO4.

  76. 76.AgBr, with Ksp = 1.0 × 10^(−12), is placed in 0.020 M KBr. What is the approximate molar solubility?

  77. 77.Two beakers contain AgCl, Ksp = 1.0 × 10^(−10). Beaker 1 is pure water. Beaker 2 is 1.0 × 10^(−3) M NaCl. Which beaker has the lower solubility of AgCl?

  78. 78.SrSO4 has Ksp = 9.0 × 10^(−8). What is its molar solubility in 0.030 M Na2SO4?

  79. 79.Adding NaCl to a saturated solution of AgCl, Ksp = 1.0 × 10^(−10), shifts AgCl(s) ⇌ Ag+ + Cl−. What happens to the molar solubility?

  80. 80.AgI has Ksp = 1.0 × 10^(−16). Compare its solubility in 1.0 × 10^(−4) M NaI with its solubility in 1.0 × 10^(−2) M NaI.

  81. 81.BaSO4 has Ksp = 1.0 × 10^(−10). In pure water its solubility is 1.0 × 10^(−5) M. In 1.0 × 10^(−3) M Ba(NO3)2, what is the approximate solubility?

  82. 82.AgCl has Ksp = 1.0 × 10^(−10). A mixture has [Ag+] = 1.0 × 10^(−4) M and [Cl−] = 1.0 × 10^(−4) M. Will AgCl precipitate?

  83. 83.CaCO3 has Ksp = 4.0 × 10^(−8). A solution has [Ca2+] = 1.0 × 10^(−5) M and [CO3^2−] = 1.0 × 10^(−5) M. Will a precipitate form?

  84. 84.PbSO4 has Ksp = 1.0 × 10^(−8). Mixing gives [Pb2+] = 2.0 × 10^(−3) M and [SO4^2−] = 2.0 × 10^(−3) M. Does PbSO4 precipitate?

  85. 85.AgBr has Ksp = 1.0 × 10^(−12). After mixing, [Ag+] = 1.0 × 10^(−7) M and [Br−] = 1.0 × 10^(−7) M. Will AgBr precipitate?

  86. 86.A 1:1 salt has Ksp = 1.0 × 10^(−10). The mixture has [M+] = 1.0 × 10^(−5) M and [X−] = 1.0 × 10^(−5) M. What is true of Q and Ksp?

  87. 87.SrSO4 has Ksp = 9.0 × 10^(−8). A solution is made with [Sr2+] = 3.0 × 10^(−3) M and [SO4^2−] = 3.0 × 10^(−3) M. Will SrSO4 precipitate?

  88. 88.AgI has Ksp = 1.0 × 10^(−16). A mixture has [Ag+] = 1.0 × 10^(−9) M and [I−] = 1.0 × 10^(−9) M. Does a precipitate form?

  89. 89.A 1:1 salt has Ksp = 1.0 × 10^(−6). After mixing, [cation] = 2.0 × 10^(−2) M and [anion] = 2.0 × 10^(−2) M. Will the salt precipitate?

  90. 90.BaSO4 has Ksp = 1.0 × 10^(−10). A trial mixture has [Ba2+] = 1.0 × 10^(−6) M and [SO4^2−] = 1.0 × 10^(−6) M. What happens?

  91. 91.Sodium acetate is the salt of sodium hydroxide, a strong base, and acetic acid, a weak acid. What is the pH character of NaCH3COO(aq) at 25°C?

  92. 92.Potassium nitrate is formed from potassium hydroxide, a strong base, and nitric acid, a strong acid. What is the pH of KNO3(aq) at 25°C?

  93. 93.Sodium fluoride comes from sodium hydroxide, a strong base, and hydrofluoric acid, a weak acid. Which description of NaF(aq) is correct?

  94. 94.Lithium bromide is the salt of lithium hydroxide, a strong base, and hydrobromic acid, a strong acid. What is true of LiBr(aq) at 25°C?

  95. 95.NaCl comes from NaOH and HCl, both strong. NaCN comes from NaOH, a strong base, and HCN, a weak acid. At the same concentration, which solution is basic?

  96. 96.Sodium chloride is prepared from hydrochloric acid and sodium hydroxide, both strong. What is the pH of NaCl(aq) at 25°C?

  97. 97.Potassium acetate has parents KOH (strong base) and acetic acid (weak acid). Potassium chloride has parents KOH and HCl, both strong. Which salt gives the higher pH?

  98. 98.A solution contains the salt of nitric acid and potassium hydroxide, both strong. What do the ions do in water?

  99. 99.Sodium hypochlorite is the salt of sodium hydroxide, a strong base, and hypochlorous acid, a weak acid. What is the acid-base character of NaClO(aq)?

  100. 100.Diprotic acid H2A has Ka1 = 1.0 × 10^(−3) and Ka2 = 1.0 × 10^(−8). Which statement is correct?

  101. 101.For diprotic acid H2B, pKa1 = 2 and pKa2 = 7. Which dissociation constant is larger?

  102. 102.Using the rounded values Ka1 = 1.0 × 10^(−2), Ka2 = 1.0 × 10^(−7), and Ka3 = 1.0 × 10^(−12) for phosphoric acid, which Ka is the largest?

  103. 103.Why is Ka1 greater than Ka2 for a diprotic acid H2A?

  104. 104.Acid H2C has Ka1 = 1.0 × 10^(−4) and Ka2 = 1.0 × 10^(−9). Which ion forms more readily from H2C, HC− or C^2−?

  105. 105.A student says Ka1 and Ka2 are both 1.0 × 10^(−5) for diprotic acid H2D. A table lists Ka1 = 1.0 × 10^(−5) and Ka2 = 1.0 × 10^(−10). Which correction is right?

  106. 106.Using Ka1 = 1.0 × 10^(−2) and Ka2 = 1.0 × 10^(−7) for diprotic sulfurous acid, which pKa is smaller?

  107. 107.Hydrogen sulfide is diprotic, with Ka1 = 1.0 × 10^(−7) and Ka2 = 1.0 × 10^(−13). Which step contributes more H3O+ when H2S dissolves in water?

  108. 108.Using Ka1 = 1.0 × 10^(−1) and Ka2 = 1.0 × 10^(−4) for diprotic oxalic acid, how many times larger is Ka1 than Ka2?