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By definition, strong acids and bases are 100% ionized in water solution. Ioniza

ID: 504056 • Letter: B

Question

By definition, strong acids and bases are 100% ionized in water solution. Ionization of a strong acid gives rise to H^+ ions, and ionization of a strong base produces OH^- ions. The equilibrium constant for a strong acid or strong base is undefined, since the reaction the ionization is complete. There is no equilibrium!. In nearly all cases of practical interest the [H^+] for a strong acid (or the [OH^-] for a strong base) is determined completely by the stoichiometry of the reaction. Once the [OH^-] or pOH is known for a base, the [H^+] or the pH of the base may be calculated using Eq(1) and/or Eq(5). Complete the following table: Calculate the pH of a 0.0430 M HNO_3 solution. pOH. [OH^-]

Explanation / Answer

Recall that:

if pH < 7, acidic, pH > 7, basic, pH = 7 neutral

pH = 14-pOH

[H+] = 10^-pH

so...

a)

pH = -log(H+) = -log(5.4*10^-4) = 3.2676

pOH = 14-3.2676 = 10.7324

[OH-] = 10^-pOH = 10^-10.7324 =1.8518*10^-11

thi is acidic

b)

pOH = -log(OH) = -log(7.8*10^-10)

pOH = 9.107

pH = 14-pOH = 14-9.107 = 4.893

[H+] = 10^-4.893 = 0.00001279

this is acidic

c)

pH = 10.75

pOH = 14-10.75 = 3.25

this is basic

[H+] = 10^-10.75 =1.7782*10^-11

[OH-] = 10^-3.25 = 0.000562

d)

pOH = 5

pH = 14-5 = 9

[H+] = 10^-9

[OH-] = 10^-5

this is basic