Brønsted–Lowry definition is more widely used: • A Brønsted–Lowry acid is a proton (H + ) donor . • A Brønsted–Lowry base is a proton (H + ) acceptor . H 3 O + ( aq ) + Cl − ( aq ) HCl( g ) + H 2 O( l ) This proton is donated. • HCl is a Brønsted–Lowry acid because it donates a proton to the solvent water. • H 2 O is a Brønsted–Lowry base because it accepts a proton from HCl.
Bronsted and Lowry acid must contain a hydrogen atom . Common B-L acids:
• A monoprotic acid contains one acidic proton. • A diprotic acid contains two acidic protons. • A triprotic acid contains three acidic protons. • A Brønsted–Lowry acid may be neutral or it may carry a net positive or negative charge. Mono-, Di-, Triprotic Acids
Mono-, Di-, Triprotic Acids Classify the following acids: HCl, HF, HNO 3 H 2 CO 3 , H 2 SO 4 H 3 PO 4 CH 3 CH 2 COOH Some acids may appear to have numerous H + ions to donate, but be careful!
Mono-, Di-, Triprotic Acids Acetic acid: HC 2 H 3 O 2 has only one H to donate The other H atoms are strongly bonded to Carbon atoms ( slightly polar bond) Acidic H atom is bonded to
• Acetic acid, CH 3 COOH, contains several H atoms • The H atom of the OH group is the acidic proton that is donated. H O | // H - C C | \ H O- H
Brønsted–Lowry Bases 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
Brønsted–Lowry Bases ( B : ) • is a proton acceptor • Must contain a lone pair of electrons that can be donated to form a new bond. • Hydroxide (OH - ) which contains an oxygen atom with 3 lone pairs of electrons, is most common Brønsted–Lowry Base.
Brønsted–Lowry Bases 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:
bases in consumer Products
Proton Transfer The Reaction of a Brønsted–Lowry Acid with a Brønsted–Lowry Base H A + B A − H B + + acid base
Conjugate (coupled) acid-base pairs: • Chemical formulas differ by one H + ion • Cation products are usually the conjugate acid • Anion products are usually the conjugate base
Proton Transfer The Reaction of a Brønsted–Lowry Acid with a Brønsted–Lowry Base H A + B A − H B + + gain of H + acid base conjugate base conjugate acid loss of H +
Proton Transfer The Reaction of a Brønsted–Lowry Acid with a Brønsted–Lowry Base H Br + + H 2 O Br − H 3 O + • The net charge must be the same on both sides of the equation.
Proton Transfer The Reaction of a Brønsted–Lowry Acid with a Brønsted–Lowry Base Amphoteric compound : A compound that contains both a H atom and a lone pair of e − it can be either an acid or a base.
- Winter '20