Acids, Bases, & Salts

Properties  Taste Sour.  Can sting skin if open (cut).  React with metals to produce H 2 gas.  Disassociate in water to produce ions that conduct electricity. (ELECTROLYTE)  Acids cause indicators to change color. Blue litmus paper turns red!

Properties  Taste Bitter.  Feel slippery to touch.  Do not react with metals.  Disassociate in water to produce ions that conduct electricity. (ELECTROLYTE)  Bases cause indicators to change color. Red litmus paper turns blue!

&

 Neutralize each other in what is called a Neutralization Reaction. &

Arrhenius AcidsArrhenius Acids form hydrogen ions (H + ) HCl (hydrochloric acid)HCl (hydrochloric acid) HNO 3 (nitric acid)HNO 3 (nitric acid) HC 2 H 3 O 2 (acetic acid)HC 2 H 3 O 2 (acetic acid) H 2 SO 4 (sulfuric acid)H 2 SO 4 (sulfuric acid) H 2 CO 3 (carbonic acid)H 2 CO 3 (carbonic acid) H 3 PO 4 (phosphoric acid)H 3 PO 4 (phosphoric acid) Definitions

Arrhenius BasesArrhenius Bases form hydroxide ions (OH - ) NaOH (sodium hydroxide)NaOH (sodium hydroxide) KOH (potassium hydroxide)KOH (potassium hydroxide) Mg(OH) 2 (magnesium hydroxide)Mg(OH) 2 (magnesium hydroxide) Ca(OH) 2 (calcium hydroxide)Ca(OH) 2 (calcium hydroxide) Ba(OH) 2 (barium hydroxide)Ba(OH) 2 (barium hydroxide) OH! It’s a base! Definitions

 Always produce a salt and water & HCl + NaOH  NaCl + H 2 O ACID + BASE  SALT + WATER

&

Definitions  Brønsted-Lowry HCl + H 2 O  Cl – + H 3 O + AcidsAcids are hydrogen ion (H + ) donors. BasesBases are hydrogen ion (H + ) acceptors. baseacid

Definitions  Types of Acids: Monoprotic AcidsMonoprotic Acids – have 1 proton to donate. Diprotic AcidsDiprotic Acids – have 2 protons to donate. Triprotic AcidsTriprotic Acids – have 3 protons to donate. HCl, HNO 3, HF H 2 SO 4, H 2 CO 3, H 2 S H 3 PO 4

Hydronium Ion Produced when an acid dissociates in water and the water picks up the hydrogen ion. H3O+H3O+ H HHHH H Cl OO – +

Brønsted-Lowry Acids & Bases

What part does water play? H 2 O + HNO 3  H 3 O + + NO 3 – AcidBase

What part does water play? can act as an acid or a base.  Water is amphoteric: can act as an acid or a base. NH 3 + H 2 O  NH OH - BaseAcid

Conjugate Acid – Base Pairs  When a base gains a proton, it becomes its conjugate acid.  When an acid loses a proton, it becomes its conjugate base. HCl + H 2 O  Cl – + H 3 O + conjugate acid conjugate base baseacid

Conjugate Acid – Base Pairs  Pairs are joined together by the loss and gain of a proton.  Acid & Base – Reactants side.  Conjugate Base & Conjugate Acid – Products side. NH 3 + H 2 O  NH OH - acid base conjugate acid conjugate base

Strength of Conjugate Acid-Base Pairs The stronger the acid … The weaker its conjugate base. The weaker its conjugate acid. The stronger the base …

Conjugate Acid – Base Pairs

Determining Strengths of Acids and Bases

Strength  Strong Acids – Dissociate almost completely in water to produce H 3 O + ions  Strong Bases – Strongly attract hydrogen ions in water, thus leaving OH HCl HNO 3 H 2 SO 4 NaOH KOH HBr HI HClO 4 STRONG ACIDS STRONG BASES Ca(OH) 2 CaO

Strength  Weak Acids – Dissociate slightly in water to produce H 3 O + ions. Do not readily dissociate.  Weak Bases – react only partially with water to form OH - ions. NH 3 H 2 NNH 2 WEAK ACIDS WEAK BASES 2- CO PO HF CH 3 COOH H 3 PO 4 H 2 CO 3 HCN

HCl + H 2 O  H 3 O + + Cl – HC 2 O + H 2 O H 3 O + + OH - Strong Acid: SINGLE ARROW DOUBLE ARROW Weak Acid: HC 2 H 3 O 2 + H 2 O H 3 O + + C 2 H 3 O 2 – HC 2 H 3 O 2 + H 2 O H 3 O + + C 2 H 3 O 2 –

CaO  Ca 2+ + O 2– HC 2 O + H 2 O H 3 O + + OH - Strong Base: SINGLE ARROW DOUBLE ARROW Weak Base: CO H 2 O O 2– + H 2 O  2OH – HCO OH –

Strong & Weak

Acid Dissociation Constant K a = [H 3 O + ][A - ] [HA] KaKa is a measure of the strength of an acid. HA (aq) + H 2 O ( l ) The greater the K a, the stronger the acid! H 3 O + (aq) + A – (aq)

Each ionization results in a different K a value. If the acid is diprotic or triprotic, the loss of each hydrogen is a separate ionization.

Base Dissociation Constant K b = [HB][OH - ] [B] KbKb is a measure of the strength of a base. B (aq) + H 2 O ( l ) HB (aq) + OH – (aq) The greater the K b, the stronger the base!

Practice Problem #1 Acetic acid is a weak monoprotic acid. If the initial concentration of acetic acid is M and the equilibrium concentration of H 3 O + is M, calculate K a for acetic acid. K a = [ H 3 O + ][A - ] [ HA ] HA (aq) + H 2 O ( l ) H 3 O + (aq) + A – (aq)

Practice Problem #1 K a = [ H 3 O + ][A - ] [ HA ] HA (aq) + H 2 O ( l ) H 3 O + (aq) + A – (aq) Use Stoichiometry! The reaction produces an A - ion for every H 3 O + ion. [ H 3 O + ] = [A - ]

Practice Problem #1 K a = [ H 3 O + ][A - ] [ HA ] HA (aq) + H 2 O ( l ) H 3 O + (aq) + A – (aq) The equilibrium concentration of HA equals its initial concentration minus the amount that ionizes. [HA] = 0.200M – M [HA] = M

Practice Problem #1 K a = [ H 3 O + ][A - ] [ HA ] HA (aq) + H 2 O ( l ) H 3 O + (aq) + A – (aq) [H 3 O + ] = [A - ] = M [HA] = M = (0.0019M)(0.0019M) (0.1981M) = 1.8 x 10 -5

Acid-Base Properties of Salts Salts dissociate in water to form H 3 O + or OH - Knowing what type of acid and base formed the salt helps predict salt solution acid-base properties.

Acid-Base Properties of Salts RULES: Strong Acid + Strong Base Neutral Salt Strong Acid + Weak Base Weak Acid + Strong Base Weak Acid + Weak Base Acidic Salt Basic Salt Cannot predict very easily

HCl + NaOH Neutral Salt NaCl STRONG ACID & BASE

NH 3 + HCl Acidic Salt NH 4 Cl STRONG ACID WEAK BASE

NaOH + H 2 CO 3 Basic Salt Na 2 CO 3 WEAK ACID STRONG BASE