Acids and Bases Chemistry Chapter 15 Acids and Bases

Acids and Bases Some Definitions Arrhenius acids and bases  Acid:Substance that, when dissolved in water, increases the concentration of hydrogen/hydronium ions (protons, H + or H 3 O + ).  Base:Substance that, when dissolved in water, increases the concentration of hydroxide ions.

Acids and Bases Some Definitions Brønsted–Lowry: must have both 1. an Acid:Proton donor and 2. a Base:Proton acceptor

Acids and Bases The Brønsted-Lowry acid donates a proton, while the Brønsted-Lowry base accepts it. Brønsted-Lowry acids and bases are always paired. Which is the acid and which is the base in each of these rxns ?

Acids and Bases What Happens When an Acid Dissolves in Water? Water acts as a Brønsted–Lowry base and abstracts a proton (H + ) from the acid. As a result, a hydronium ion (H 3 O + ) is formed.

Acids and Bases Ionization of HCl and formation of hydronium ion, H 3 O + H 2 O + HCl  H 3 O + + Cl - Proton donor Proton acceptor

Acids and Bases A Brønsted–Lowry acid… …must have a removable (acidic) proton. HCl, H 2 O, H 2 SO 4 A Brønsted–Lowry base… …must have a pair of nonbonding electrons. NH 3, H 2 O

Acids and Bases Salts Compounds that dissociate releasing neither H + or OH - ions Example: KCl  K + + Cl -

Acids and Bases Properties of Acids  Acids taste sour  Acids affect indicators  Blue litmus turns red  Methyl orange turns red  Acids have a pH lower than 7  Acids are proton (hydrogen ion, H + ) donors  Acids react with active metals, produce H 2  Acids are electrolytes  Acids neutralize bases to produce a salt and water

Acids and Bases Acids change Indicators Blue litmus paper turns red in contact with an acid.

Acids and Bases Acids React with Active Metals Acids react with active metals to form salts and hydrogen gas. Mg + 2HCl  MgCl 2 + H 2 (g)

Acids and Bases Acids Neutralize Bases HCl + NaOH  NaCl + H 2 O Neutralization reactions ALWAYS produce a salt and water.

Acids and Bases Acids are Proton Donors Monoprotic acidsDiprotic acidsTriprotic acids HCl HC2H3O2HC2H3O2 HNO 3 H 2 SO 4 H 2 CO 3 H 3 PO 4

Acids and Bases Uses H 3 PO 4 - soft drinks, fertilizer, detergents H 2 SO 4 - fertilizer, car batteries HCl - gastric juice HC 2 H 3 O 2 - vinegar

Acids and Bases Acids you must know: Strong Acids Weak Acids Hydrochloric acid, HCl Nitric acid, HNO 3 Sulfuric acid, H 2 SO 4 Phosphoric acid, H 3 PO 4 Acetic acid, HC 2 H 3 O 2 Hydrobromic acid, HBr Hydroiodic acid, HI Perchloric acid, HClO 4

Acids and Bases Properties of Bases  Bases taste bitter  Bases affect indicators  Red litmus turns blue  Phenolphthalein turns purple  Bases have a pH greater than 7  Bases are proton (hydrogen ion, H + ) acceptors  Solutions of bases feel slippery  Bases neutralize acids to produce a salt and water

Acids and Bases Examples of Bases  Sodium hydroxide (lye), NaOH  Potassium hydroxide, KOH  Magnesium hydroxide, Mg(OH) 2  Calcium hydroxide (lime), Ca(OH) 2

Acids and Bases Uses NaOH - lye, drain and oven cleaner Mg(OH) 2 - laxative, antacid NH 3 - cleaners, fertilizer

Acids and Bases Naming Acids, Bases, Salts Bases & Salts- Ionic  Name the same as ionic compounds Acids  Binary 2 elements, first hydrogen Hydro___ic acid  Ternary 3 elements, change ending -ate  ic, -ite  ous

Acids and Bases Strong Acids vs. Weak Acids Strong acids are assumed to be 100% ionized in solution (good proton donors). Weak acids are usually less than 5% ionized in solution (poor proton donors). HClH 2 SO 4 HNO 3 H 3 PO 4 HC 2 H 3 O 2 Organic acids

Acids and Bases Strong Acid Dissociation

Acids and Bases Weak Acid Dissociation

Acids and Bases Which of the following "molecular" pictures best represents a concentrated solution of the weak acid HA? Concept Test AB

Acids and Bases pH Scale 0 7 INCREASING ACIDITY NEUTRAL INCREASING BASICITY 14 pHpH  a measure of the concentration of H 3 O + ions in solution  measured with a pH meter or an indicator with a wide color range

Acids and Bases Acids Have a pH less than 7

Acids and Bases Bases have a pH greater than 7

Acids and Bases pH Scale pH of Common Substances

Acids and Bases ACID + BASE  SALT + WATER HCl + NaOH  NaCl + H 2 O Neutralization does not always mean pH = 7. = Neutralization Reaction

Acids and Bases KOH + HNO 3  H 2 O + KNO 3 Acid? Base? Salt? HNO 3 KOH KNO 3 Neutralization Reaction

Acids and Bases Products of Neutralization HCl + NaOH  H 2 SO 4 + Ca(OH) 2  HNO 3 + KOH  The products of neutralization are always a ______ and _______. NaCl + H 2 O CaSO H 2 O KNO 3 + H 2 O salt water