<< Chapter < Page Chapter >> Page >
By the end of this section, you will be able to:
  • Identify acids, bases, and conjugate acid-base pairs according to the Brønsted-Lowry definition
  • Write equations for acid and base ionization reactions
  • Use the ion-product constant for water to calculate hydronium and hydroxide ion concentrations
  • Describe the acid-base behavior of amphiprotic substances

Acids and bases have been known for a long time. When Robert Boyle characterized them in 1680, he noted that acids dissolve many substances, change the color of certain natural dyes (for example, they change litmus from blue to red), and lose these characteristic properties after coming into contact with alkalis (bases). In the eighteenth century, it was recognized that acids have a sour taste, react with limestone to liberate a gaseous substance (now known to be CO 2 ), and interact with alkalis to form neutral substances. In 1815, Humphry Davy contributed greatly to the development of the modern acid-base concept by demonstrating that hydrogen is the essential constituent of acids. Around that same time, Joseph Louis Gay-Lussac concluded that acids are substances that can neutralize bases and that these two classes of substances can be defined only in terms of each other. The significance of hydrogen was reemphasized in 1884 when Carl Axel Arrhenius defined an acid as a compound that dissolves in water to yield hydrogen cations (now recognized to be hydronium ions) and a base as a compound that dissolves in water to yield hydroxide anions.

In an earlier chapter on chemical reactions, we defined acids and bases as Arrhenius did: We identified an acid as a compound that dissolves in water to yield hydronium ions (H 3 O + ) and a base as a compound that dissolves in water to yield hydroxide ions (OH ). This definition is not wrong; it is simply limited.

Later, we extended the definition of an acid or a base using the more general definition proposed in 1923 by the Danish chemist Johannes Brønsted and the English chemist Thomas Lowry. Their definition centers on the proton, H + . A proton is what remains when a normal hydrogen atom, 1 1 H , loses an electron. A compound that donates a proton to another compound is called a Brønsted-Lowry acid    , and a compound that accepts a proton is called a Brønsted-Lowry base    . An acid-base reaction is the transfer of a proton from a proton donor (acid) to a proton acceptor (base). In a subsequent chapter of this text we will introduce the most general model of acid-base behavior introduced by the American chemist G. N. Lewis.

Acids may be compounds such as HCl or H 2 SO 4 , organic acids like acetic acid (CH 3 COOH) or ascorbic acid (vitamin C), or H 2 O. Anions (such as HSO 4 , H 2 PO 4 , HS , and HCO 3 ) and cations (such as H 3 O + , NH 4 + , and [ Al ( H 2 O ) 6 ] 3+ ) may also act as acids. Bases fall into the same three categories. Bases may be neutral molecules (such as H 2 O, NH 3 , and CH 3 NH 2 ), anions (such as OH , HS , HCO 3 , CO 3 2− , F , and PO 4 3− ) , or cations (such as [ Al(H 2 O) 5 OH ] 2+ ) . The most familiar bases are ionic compounds such as NaOH and Ca(OH) 2 , which contain the hydroxide ion, OH . The hydroxide ion in these compounds accepts a proton from acids to form water:

Questions & Answers

what is the meaninh of link
Aisha Reply
Yes wish to join am a science ⚗ student
Emmanuel Reply
What is acid
Emmanuel
is agroup of substance that relaise hydrogen ion in the water solution.
mengistu
thanks
Aisha
An acid is a proton donor or an electron pair acceptor
amanda
how can someone understand chemistry vividly
Mercy Reply
Maybe by reading proofs or practical work and application in modern world.
Abdelkarim
what is isotopes
Samuel Reply
whats de shape of water
Amara Reply
water has no shape because it's liquid
Wil
water is a shapeless, odourless, colourless and tasteless substance that only takes the shape of its container.
mikefred
i think they're referring to the molecular shape?
It has no shape but takes the shape of the container
kpadonu
Yeah I think so too and it's a bent shape
amanda
what isthe maening pkw
Wilson Reply
what is the meaning of STP
Laura
introduction to chemistry for beginner
Lansana Reply
hi
noble
through out human history
marwan Reply
Yes?
Esther
hello
noble
yes
Bol
what
noble
is euglena a unicellular organ
Agio Reply
is euglena a unicellular organism
Agio
how is hydrogen can be heated
Buwembo Reply
what is difference between atom and molecule
Aqeela Reply
Atom is the smallest part of matter; it consists of equal number of protons and electrons. It may have neutrons. A molecule is a compound made of atoms covalently bonded.
Abdelkarim
does amoeba has structure
Mercy Reply
what is the effect of green house on the earth 🌎
kolawole Reply
what is the effect of green house on the earth 🌎
kolawole
what's an atom?
Davy Reply
it's the smallest unit of Matter
Orsine
atom
Eden
smallest part of an element
lydia
also, depending on its (atom's) structure, that is the amount of protons and neutrons and electrons, is the determining factors of what element it is.
Richard
is a smallast particals of an element
Buwembo
it is the smallest part of an element that can take part in a chemical reaction
Ayub
is the smallest part of an element
Jonathan
An atom is the smallest indivisible part of a matter
kpadonu
Oy kl konsa test hay or kitna hay?
Faisal Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play




Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Chemistry' conversation and receive update notifications?

Ask