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Strength of Acids & Bases. Self-Ionization of Water. Two water molecules can react with each other to form two ions: Hydronium Ion (H 3 O + ) Note : Hydronium ions are the same as hydrogen ions (H + ). Hydroxide Ion (OH - ). Ion Concentration of Pure Water.
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Self-Ionization of Water • Two water molecules can react with each other to form two ions: • Hydronium Ion (H3O+) • Note: Hydronium ions are the same as hydrogen ions (H+). • Hydroxide Ion (OH-)
Ion Concentration of Pure Water • Pure water always has the same concentration of hydronium and hydroxide ions. • [H3O+] represents the concentration of hydronium ions. • In pure water, [H3O+] is 1x10-7 • [OH-] represents the concentration of hydroxide ions. • In pure water, [OH-] is 1x10-7
Ion Concentrations in Solutions • In neutral solutions, concentration of hydronium ions equals concentration of hydroxide ions. • [H3O+] = [OH-] • In acidic solutions, concentration of hydronium ions is more than concentration of hydroxide ions. • [H3O+] > [OH-] • In basic solutions, concentration of hydronium ions is less than concentration of hydroxide ions. • [H3O+] < [OH-]
Strong Acids & Bases • Strong acids completely ionize when in aqueous solutions. • Produce a high concentration of hydrogen ions in solution. • HCl H+ + Cl-(100 % ions) • Strong bases completely ionize when in aqueous solutions. • Produce a high concentration of hydroxide ions in solution. • NaOH Na+ + OH-(100 % ions)
Identifying Strong Acids • Strong acids cannot be identified by their formula. • There are 6 strong acids (must be memorized!) • HCl – Hydrochloric acid. • HBr – Hydrobromic acid. • HI – Hydroiodic acid • HNO3 – Nitric Acid • H2SO4 – Sulfuric Acid • HClO4 – Perchloric Acid
Identifying Strong Bases • What do all of the strong bases below have in common? • Strong bases all have a group 1 or 2 metal with a hydroxide ion.
Weak Acids & Bases • Weak acids partially ionize in aqueous solutions. • Produce a lower concentration of hydrogen ions than strong acids. • HF H+ + F-(double arrow, NOT 100 % ions) • Weak bases partially ionize in aqueous solutions. • Produce a lower concentration of hydroxide ions than strong bases. • Cr(OH)3 Cr+3+ 3OH-(double arrow, NOT 100 % ions)