• A di protic acid contains two acidic protons. H 2 SO 4 • A tri protic acid contains three acidic protons. H 3 PO 4 H Cl
Your Turn Which of the following species can be Bronsted-Lowry acids: (a) HI (b) SO 4 2- (c) H 2 PO 4 - (d) Cl-
Brønsted–Lowry Bases 14 • A Brønsted–Lowry base is a proton acceptor , so it must be able to form a bond to a proton. • A base must contain a lone pair of electrons that can be used to form a new bond to the proton. N H H H + H 2 O( l ) N H H H H + + OH − ( aq ) Brønsted–Lowry base This e − pair forms a new bond to a H from H 2 O.
Brønsted–Lowry Bases 15 • Common Brønsted–Lowry Bases ( B: ) Na OH sodium hydroxide K OH potassium hydroxide Mg( OH ) 2 magnesium hydroxide Ca( OH ) 2 calcium hydroxide H 2 O water NH 3 ammonia Lone pairs make these neutral compounds bases. The OH − is the base in each metal salt.
The Reaction of a Brønsted – Lowry Acid with a Brønsted – Lowry Base 16 H A + B A − H B + + gain of H + acid base loss of H + This e − pair stays on A. This e − pair forms a new bond to H + .
The Reaction of a Brønsted – Lowry Acid with a Brønsted – Lowry Base 17 • When a species gains a proton ( H + ), it gains a +1 charge . H 2 O base zero charge add H + H 3 O + +1 charge • When a species loses a proton ( H + ), it effectively gains a −1 charge . HBr acid zero charge lose H + Br − −1 charge
Conjugate Acid-Base Pairs Conjugate acid: species formed when a proton (H+) is added to a Bronsted-Lowry base. Conjugate base: species that remains when a proton (H+) is removed from a Bronsted- Lowry acid.
Conjugate Acid-Base Pairs
Your Turn Identify the conjugate acid and conjugate base in the following reaction. Write the conjugate acid of: NH 3 CO 3 2- Write the conjugate base of: H 3 PO 4 HSO 4 -
Amphoteric Substances A substance that can either ___________ or __________ a proton and thus can function as either a Bronsted-Lowry acid or a Bronsted- Lowry base. Water can act as Bronsted-Lowry base Water can act as Bronsted-Lowry acid
The Reaction of a Brønsted – Lowry Acid with a Brønsted – Lowry Base 22 Amphoteric substances contain both a hydrogen atom and a lone pair of e − ; it can be either an acid or a base. H O H H 2 O as a base add H + H O H H + conjugate acid H O H H 2 O as an acid remove H + H O − conjugate base
Acid and Base Strength A _____________ acid is one that completely ionizes (or very nearly) when placed in water. A _____________ acid is one that only partially ionizes when placed in water.
24 • The splitting apart of a covalent molecule (or ionic compound) into its ions is called dissociation .
- Fall '16
- Christine Gaudinski