Acids and Bases Acids Sour Taste React with
Acids and Bases • Acids – Sour Taste – React with metal to form H 2. – Form Electrolytes in water. – Turn indicators red. • Bases – Bitter Taste – Slimey feel. – Form Electrolytes in water. – Turn indicators blue.
Types of Acids and Bases • Arrhenius • Bronsted-Lowry • Lewis
ARRHENIUS • Arrhenius said that acids are Hydrogen containing compounds that ionize to form H+ (Hydrogen ion). • Bases ionize to form OH- (Hydroxide ion).
• Arrhenius Acids – Monoprotic – 1 H (HNO 3) – Diprotic – 2 H’s (H 2 SO 4) – Triprotic – 3 H’s (H 3 PO 4) – Not all of the Hydrogen may be released in a rxn, only the very polar are ionized. – Hydrogen will join a very electronegative element. • Arrhenius Bases – Very Solubile (Na. OH, KOH) – Low Solubility Ca(OH)2, Mg(OH)2
• Arrhenius Acids – Monoprotic – 1 H (HNO 3) – Diprotic – 2 H’s (H 2 SO 4) – Triprotic – 3 H’s (H 3 PO 4) – Not all of the Hydrogen may be released in a rxn, only the very polar are ionized. – Hydrogen will join a very electronegative element. • Arrhenius Bases – Very Solubile (Na. OH, KOH) – Low Solubility Ca(OH)2, Mg(OH)2
Bronsted-Lowry Acids and Bases • Acids are Hydrogen (H+) donators and Bases are Hydrogen (H+) acceptors. – Ex: • Ammonia is very soluble in water. • It accepts H+ from H 2 O • So, water donates H+ and NH 3 accepts it.
Conjugate Acids and Bases • In a reaction, a base that gains H+ is a conjugate acid. • The product that remains is a conjugate base. • The two are always paired. • When water gains H+ it forms H 3 O. • When water donates H+ is is amphoteric.
Lewis Acids • An acid accepts a pair of electrons (e-) in a rxn and a base donates electrons. • Lewis acids form with a double bond. • Lewis bases form a covalent bond.
Hydrogen Ions and Acids • Self ionization is the dissociation of water to H+ and OH-. • H+ always form H 3 O. • Neutral water solutions contain equal amounts of H 3 O+ and OH-.
Ion-Product Constant (water) Kw = H+ x OH- = 1. 0 x 10 -14 • Acidic solutions have more H+ than OH-. • Basic Solutions have less H+ than OH-. • The latter is also known as alkaline. • p. H is an expression of the amount of H+. p. H = - log [ H+] 1. 0 x 10 -7 (neutral)
Strength of Acids and Bases • Strong Acids are completely ionized. • Weak Acids are slightly ionized. – SA = High Ka – WA = Low Ka • Strong Bases are completely ionized. • Weak Bases are slightly ionized. – SB = High Kb – WB = Low Kb Note: concentration and strength are different.
Neutralization/Titration • Acid/Base reactions form salts. – SA + SB = Neutral Salt – WA + WB = Neutral Salt • Titration finds the equivalence point where molar ratios are not 1: 1. – Here, a known acid or base strength is made a standard solution to find the strength of the other. – The end point has a color change indicating neutralization.
Salts in Solution • A salt has a cation bonded to an anion due to an A/B rxn. • Hydrolysis is dissociation of a salt into an A/B. – Salts that form acids donate protons. – Salts that form bases attract protons. • A buffer is a solution whose p. H remains fairly constant when A/B is added. – Buffer = WA + Salt – Buffer = WB + Salt
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