7.8 - Acid-Base Properties of Salts
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| Define "salt" | Ionic compound
Breaks up into ions when dissolved in water - ions move independently in dilute solns.
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| Why don't anions such as Cl- and NO3- combine with H+ when placed in water? | Conjugate bases of strong acids are extremely weak, so these anions don't have much affinity for [H+].
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| Why don't cations such as K+ or Na+ affect pH? | Conjugate acids of strong bases are extremely weak, so these cations don't produce (or attract) H+
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| T/F Salts that consist of the cations of strong bases and the anions of strong acids have no effect on [H+] when dissolved in water. | True
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| Aqueous solutions of salts such as KCl, NaCl, NaNO3, and KNO3 have a pH of ... | 7. -Cl belongs to a strong acid, Na+ belongs to a strong base, and so on.
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| For any weak acid and its conjugate base, Ka x Kb = | Kw
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| For any salt whose cation has neutral properties (ex. Na+ or K+) and whose anion is the conjugate base of a weak acid, the aqueous solution will be ... | basic.
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| How do you predict whether a solution will be acidic, basic, or neutral if both ions affect the pH of the aqueous solution? | See if Ka or Kb is larger. If Ka is larger, it'll be acidic. If Kb is larger, it'll be basic.
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| Explain pH and characteristics. KCl, KNO3, NaCl, NaNO3 | Anions belong to strong bases, making them negligible. Cations belong to strong bases, making them also negligible. pH is 7.
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| Explain pH and characteristics. NaC2H3O2, KCN, NAF | Cations belong to strong bases, making them negligible. Anions belong to weak acids, meaning the conjugate bases are strong, meaning the solution will be basic.
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| Explain pH and characteristics. NH4Cl, NH4NO3 | Cations are acids. Anions belong to strong acids, making them negligible. Acidic solution.
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| Explain pH and characteristics. NH4C2H3O2, NH4CN | Anions are the conjugate bases of weak acids. Cations are acids.
If Ka > Kb, then the solutions were acidic. If Ka < Kb, then the solutions were basic.
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| Explain pH and characteristics. AL(NO3)3, FeCl3 | Hydrated cation acts as an acid. Anion has no effect on pH b/c they're the conjugate bases of strong acids. Acidic solution.
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| Predict whether an aqueous solution of each of the following salts will be acidic, basic, or neutral. NH4C2H3O2 | NH4 is a weak acid, so it has a strong conjugate base. C2H3O2 is the strong conjugate base of a weak acid. HOWEVER, Ka = Kb, so the solution is neutral.
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| Predict whether an aqueous solution of each of the following salts will be acidic, basic, or neutral. NH4CN | NH4 is a weak acid. CN is the strong conjugate base of a weak acid. So it'll be basic.
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| Predict whether an aqueous solution of each of the following salts will be acidic, basic, or neutral. Al2(SO4)3 | Solution will contain Al(H2O)6 3+ and SO4 2- ions. Ka is 1.4 x 10^-5 and Kb can be found by taking Kw and dividing by Ka2 for sulfuric acid. Kb = 8.3 x 10^-13
So, it'll be acidic.
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