Chapter 8 - Acids, Bases, and pH

The Arrhenius Theory of Acids and Bases: * An acid is a substance that dissociates in water to form H+ * A base is a substance that dissociates in water to form OH−
Hydronium ion, H3O+(aq): hydrated proton * Makes hydrogen bonds with water
Brønsted-Lowry theory: * Acid is a substance a proton can be removed (proton-donors) * The base is a substance that accepts a proton (proton-acceptors)
Conjugate acid-base pair: substances that differ with a proton * Conjugate acid: the proton is added to the base * Conjugate base: the proton is removed from the acid
Amphoteric: a substance that can act as a proton donor in one reaction and a base in another
Strong acids: * Hydrohalic acids: (HCl, HBr,) have hydrogen-bonded to atoms * Oxoacids: number of oxygen atoms by two or more * Increase in strength with more oxygen atoms
Monoprotic acids: single hydrogen atoms that dissociate in water
Polyprotic acids: more than one hydrogen atom that dissociates
Strong bases**:** * Oxides and hydroxide of alkali metals * Alkaline earth metal oxides and hydroxides below beryllium
Strong acids and bases (strong electrolytes dissociate in water * Can’t find a concentration of weak acids and bases

Equilibrium constant Kc for dissociation of water: * Kc = ( [H3O+][OH−] ) / [H2O]2 * Kc [H2O]2 = product of concentration of hydronium ions and hydroxide ions
Ion product constant for water, Kw: product of [H3O+][OH−] * Equal to 1.0 x 10-14 mol/L
Acids solution: mol/L * [H3O+] > 1.0 x 10-7 mol/L * [OH−] < 1.0 x 10-7 mol/L
Neutral solution: * [H3O+] = 1.0 x 10-7 mol/L * [OH−] = 1.0 x 10-7 mol/L
Basic solution: * [H3O+] < 1.0 x 10-7 mol/L * [OH−] > 1.0 x 10-7 mol/L
pH: exponential power of hydrogen/ hydronium ions, in moles per litre * pH = -log[H3O+]
pOH: power of hydroxide ions of a solution from the [OH−] * pOH = −log[OH−]
Kw = [H3O+][OH−] = 1.0 x 10-14 mol/L at 25 ̊C
∴ pH + pOH = 14
[H3O] = 10−pH
[OH−] = 10−pOH
Acid dissociation constant, Ka: acid ionization constant, measures the strength of the acid * Kc[H2O] = Ka = ( [H3O+][A−] ) / [HA]
Percent dissociation: fraction of acid molecules that dissociate compared with the initial concentration of the acid, expressed as a percent depends on Ka and initial concentration of weak acid
Polyprotic acids pH calculated for the first dissociation are used in the second dissociation and again for as many steps required

Base dissociation constant, Kb: base ionization constant, measures strength of base Kb = ( [[HB+][OH−] ) / [B]
Buffer solution: a solution that contains a weak acid/conjugate base mixture or a weak base/conjugate acid mixture made by:Using weak acid and its salting weak base and its salt Characteristics: Unchanging pHBuffer capacity: the amount of acid or base that can be added before the considerable change occurs to the pH

Acid-base titration curve: a graph of the pH of an acid (or base) against the volume of an added base
Titrations: analytical procedures, usually to find: * Equivalence point: point in a titration when the acid and base that are present completely react with each other * Can help calculate unknown concentrations * Indicators can be used to find endpoints close to the equivalence point * Strong acid with strong acid * Equivalence of pH of 7 * Weak acid and strong base * Equivalence of pH of above 7 * Weak base with strong acid * Equivalence of pH below 7