A. Acids and Bases The Arrhenius Model Acid – produces hydrogen ions in aqueous solution Base – produces hydroxide ions in aqueous solution Macid * Vml (acid) = Mbase * Vml (base) Mbase * Vml (base) = Macid * Vml (acid) Macid = Mbase * Vml (base) Mbase = Macid * Vml (acid) Vml (acid) Vml (base)

The Bronsted-Lowry Model Acid – proton donor Base – proton acceptor The general reaction for an acid dissolving in water is

The Bronsted-Lowry Model Conjugate acid-base pair

The Bronsted-Lowry Model Water acts as a base accepting a proton from the acid. Forms hydronium ion (H3O+)

B. Acid Strength Strong acid – completely ionized or completely dissociated

Weak acid – most of the acid molecules remain intact

A strong acid contains a relatively weak conjugate base. A weak acid contains a relatively strong conjugate base.

Common strong acids are Sulfuric acid, H2SO4 Hydrochloric acid, HCl Nitric acid, HNO3 Perchloric acid, HClO4

C. Water as an Acid and a Base Product of [H3O+] and [OH] is always constant.

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[ ] = molarity D. The pH Scale The “p scale” is used to express small numbers. pH = log [H+] [ ] = molarity

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Because the pH scale is a log scale based on 10, the pH changes by 1 for every power of 10 change in the [H+].

D. The pH Scale *

pOH scale pOH = log [OH] pH + pOH = 14.00

* E. Measuring pH Indicators – substances that exhibit different colors in acidic and basic solutions In an acid solution the indicator will be in the HIn form. In a basic solution the indicator will be in the In form.

F. Acid-Base Titrations Titration – delivering a measured volume of a solution of known concentration into the solution being analyzed Titrant – a standard solution Buret – device used for accurate measurement of the delivery of a liquid Stoichiometric point (equivalence point) – when just enough titrant has been added to react with all of the solution being analyzed

Titration curve (pH curve) – plot of the data (pH vs volume) for a titration *

G. Buffered Solutions Buffered solution – resists a change in its pH when either and acid or a base has been added Presence of a weak acid and its conjugate base buffers the solution

Titration