<< Chapter < Page Chapter >> Page >
By the end of this section, you will be able to:
  • Predict whether a salt solution will be acidic, basic, or neutral
  • Calculate the concentrations of the various species in a salt solution
  • Describe the process that causes solutions of certain metal ions to be acidic

As we have seen in the section on chemical reactions, when an acid and base are mixed, they undergo a neutralization reaction. The word “neutralization” seems to imply that a stoichiometrically equivalent solution of an acid and a base would be neutral. This is sometimes true, but the salts that are formed in these reactions may have acidic or basic properties of their own, as we shall now see.

Acid-base neutralization

A solution is neutral when it contains equal concentrations of hydronium and hydroxide ions. When we mix solutions of an acid and a base, an acid-base neutralization reaction occurs. However, even if we mix stoichiometrically equivalent quantities, we may find that the resulting solution is not neutral. It could contain either an excess of hydronium ions or an excess of hydroxide ions because the nature of the salt formed determines whether the solution is acidic, neutral, or basic. The following four situations illustrate how solutions with various pH values can arise following a neutralization reaction using stoichiometrically equivalent quantities:

  1. A strong acid and a strong base, such as HCl( aq ) and NaOH( aq ) will react to form a neutral solution since the conjugate partners produced are of negligible strength (see [link] ):
    HCl ( a q ) + NaOH ( a q ) NaCl ( a q ) + H 2 O ( l )
  2. A strong acid and a weak base yield a weakly acidic solution, not because of the strong acid involved, but because of the conjugate acid of the weak base.
  3. A weak acid and a strong base yield a weakly basic solution. A solution of a weak acid reacts with a solution of a strong base to form the conjugate base of the weak acid and the conjugate acid of the strong base. The conjugate acid of the strong base is a weaker acid than water and has no effect on the acidity of the resulting solution. However, the conjugate base of the weak acid is a weak base and ionizes slightly in water. This increases the amount of hydroxide ion in the solution produced in the reaction and renders it slightly basic.
  4. A weak acid plus a weak base can yield either an acidic, basic, or neutral solution. This is the most complex of the four types of reactions. When the conjugate acid and the conjugate base are of unequal strengths, the solution can be either acidic or basic, depending on the relative strengths of the two conjugates. Occasionally the weak acid and the weak base will have the same strength, so their respective conjugate base and acid will have the same strength, and the solution will be neutral. To predict whether a particular combination will be acidic, basic or neutral, tabulated K values of the conjugates must be compared.

Stomach antacids

Our stomachs contain a solution of roughly 0.03 M HCl, which helps us digest the food we eat. The burning sensation associated with heartburn is a result of the acid of the stomach leaking through the muscular valve at the top of the stomach into the lower reaches of the esophagus. The lining of the esophagus is not protected from the corrosive effects of stomach acid the way the lining of the stomach is, and the results can be very painful. When we have heartburn, it feels better if we reduce the excess acid in the esophagus by taking an antacid. As you may have guessed, antacids are bases. One of the most common antacids is calcium carbonate, CaCO 3 . The reaction,

CaCO 3 ( s ) + 2 HCl ( a q ) CaCl 2 ( a q ) + H 2 O ( l ) + CO 2 ( g )

not only neutralizes stomach acid, it also produces CO 2 ( g ), which may result in a satisfying belch.

Milk of Magnesia is a suspension of the sparingly soluble base magnesium hydroxide, Mg(OH) 2 . It works according to the reaction:

Mg ( OH ) 2 ( s ) Mg 2+ ( a q ) + 2 OH ( a q )

The hydroxide ions generated in this equilibrium then go on to react with the hydronium ions from the stomach acid, so that :

H 3 O + + OH 2 H 2 O ( l )

This reaction does not produce carbon dioxide, but magnesium-containing antacids can have a laxative effect.

Several antacids have aluminum hydroxide, Al(OH) 3 , as an active ingredient. The aluminum hydroxide tends to cause constipation, and some antacids use aluminum hydroxide in concert with magnesium hydroxide to balance the side effects of the two substances.

Questions & Answers

what does the term carbon-12 scale mean
Amanda Reply
what are the six types of elements
Rebecca Reply
which table is flammable
Blessing Reply
I haven't gotten to tables o 😥
Rebecca
pls how can I give an IUPAC nomenclature in organic chemistry
Moshood Reply
Paul's exclusion principle
Anuforo Reply
what do you mean by d block ,give more details element
Agburum Reply
d block elements are also called transition metals. It includes elements from group 3-12 and d block elements hold up to 10 electrons in their shell
Amanda
all?
Davy
yea
Amanda
Define chemical formula
Kevin Reply
they are the mathematical representation of chemicals I guess
Uche
Bohr model of hydrogen atom
Muhammad Reply
what is important of this model
nagesh
what is the main reaction between sodium and chlorine
Akeem Reply
when a sodium atom is transferred an electron to a chloride atom forming a sodium cation and a chlorde anoin both ions are compltely valence shells and a energetically more stable this reaction is extremely more exothermic producing a bright yellow light abd a great deal of heat energy
sani
well what kind of sodium
coland
sodium chloride
coland
Tyropanoic acid and its salt sodium tyropanoate are radiocontrast agents used in cholecystography (X-ray diagnosis of gallstones). Trade names include Bilopaque, Lumopaque, Tyropaque, and Bilopac. The molecule contains three heavy iodine atoms which obstruct X-rays in the same way as the calcium in
coland
Sodium tetradecyl sulfate (STS) is a commonly used synonym for 7-ethyl-2-methyl-4-undecanyl sulfate sodium salt which is anionic surfactant that is the active component of the sclerosant drug Sotradecol. It is commonly used in the treatment of varicose and spider veins of the leg, during the procedu
coland
Sodium stibogluconate, sold under the brand name Pentostam among others, is a medication used to treat leishmaniasis. This includes leishmaniasis of the cutaneous, visceral, and mucosal types. Some combination of miltefosine, paramycin and liposomal amphotericin B; however, may be recommended due to
coland
Sodium picosulfate (INN, also known as sodium picosulphate) is a Contact stimulant laxative used as a treatment for constipation or to prepare the large bowel before colonoscopy or surgery. It is sold under the trade names Sodipic Picofast, Laxoberal, Laxoberon, Purg-Odan, Picolax, Guttalax, Namilax
coland
Ipodate sodium (sodium iopodate) is an iodine-containing radiopaque contrast media used for X-rays. The drug is given orally and the resulting contrast allows for easy resolution of the bile duct and gall bladder. Other uses Although not FDA approved, ipodate sodium has been used to treat Graves'
coland
Sodium ferric gluconate complex (brand name ferrlecit by Sanofi), is an intravenously administered iron product indicated in the treatment of iron deficiency anemia. It is frequently used in patients undergoing hemodialysis, those undergoing erythropoietin therapy, and/or patients who have chronic k
coland
Dehydrocholic acid is a synthetic bile acid, manufactured by the oxidation of cholic acid. It acts as a hydrocholeretic, increasing bile output to clear increased bile acid load.
coland
Ethylenediaminetetraacetic acid (EDTA), also known by several other names, is an aminopolycarboxylic acid and a colourless, water-soluble solid. Its conjugate base is ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ("s
coland
Sodium aurothiomalate (INN, known in the United States as gold sodium thiomalate) is a gold compound that is used for its immunosuppressive anti-rheumatic effects. Along with an orally-administered gold salt, auranofin, it is one of only two gold compounds currently employed in modern medicine. Med
coland
Sodium ascorbate is one of a number of mineral salts of ascorbic acid (vitamin C). The molecular formula of this chemical compound is C6H7NaO6. As the sodium salt of ascorbic acid, it is known as a mineral ascorbate. It has not been demonstrated to be more bioavailable than any other form of vitamin
coland
Diatrizoic acid (or its anionic form, diatrizoate), also known as amidotrizoic acid, or 3,5-diacetamido-2,4,6-triiodobenzoic acid, is a radiocontrast agent containing iodine. Trade names include Hypaque, Gastrografin, Iothalmate and Urografin, the latter being a combination of the sodium and meglum
coland
Sodium acetrizoate (rINN, trade names Urokon, Triurol and Salpix), the sodium salt of acetrizoic acid, is a high-osmolality, water-soluble, iodine-based radiographic contrast medium no longer in clinical use. Acetrizoate was developed by V.H. Wallingford of Mallinckrodt, and introduced in 1950; it
coland
i think some was missed
coland
what chlorine L-Alpha glycerylphosphorylcholine (alpha-GPC, choline alfoscerate) is a natural choline compound found in the brain. It is also a parasympathomimetic acetylcholine precursor which may have potential for the treatment of Alzheimer's disease and other dementias. Alpha-GPC rapidly delive
coland
Choline Theophyllinate , also known as oxtriphylline, is a cough medicine derived from xanthine that acts as a bronchodilator to open up airways in the lung. Chemically, it is a salt of choline and Theophylline. It classifies as an expectorant. The drug is available under the brand names Choledyl an
coland
Choline (/ˈkoʊlin/) is a water-soluble vitamin. It is usually grouped within the B-complex vitamins. The term cholines refers to the class of quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation (X− on the right denotes an undefined counteranion). The cation appears in the
coland
thanks
sani
please what is redox reaction
BABARINDE
hydrogen reacting with water
Iyenge Reply
what is matter
Godgift Reply
matter is anything that has Mass and can occupy space
Moshood
apart from those device there is there any device
Eke Reply
how many elements do we have
ARUOTURE Reply
Modern Electronic Theory
Levi Reply
a new way or an improvement in modern electrical products.
Andrew
find the volume of oxygen produced from the electrolysis of acidified water of a current of a 2A was passed through the electrolysis of acidified water for 2 hours
Ngwu Reply
14400J
Ese
wrong question, go through it. oxygen cannot be produced.
Andrew

Get the best Chemistry course in your pocket!





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