14.1 Brønsted-Lowry Acids and Bases

• You will be able to identify acids, bases, and conjugate acid-base pairs by the end of this section.
• When Robert Boyle characterized them in 1680, he noted that acids dissolved many substances, changed the color of natural dyes, and lost their characteristic properties after coming into contact with alkalis.
• Acidic acids have a sour taste, react with limestone to liberate a gaseous substance, and interact with alkalis to form neutral substances.
• The development of the modern acid-base concept was greatly aided by the work of Humphry Davy.
• According to Joseph Louis Gay-Lussac, acids are substances that can neutralize bases and that these two classes of substances can only be defined in terms of each other.
• In 1884, the significance of hydrogen was emphasized when it was defined as a compound that dissolved in water to produce hydrogen cations and a base that dissolved in water to produce 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 dissolved in water and a base as a compound that dissolved in water.
• This definition is limited.

• The more general definition of an acid or a base was proposed in 1923 by Johannes Bronsted and the English chemist Thomas Lowry.
• A normal hydrogen atom, 11H, loses an electron.
• The transfer of a protons from a donor to a acceptor is called an acid-base reaction.
• The most general model of acid-base behavior was introduced by the American chemist G. N. Lewis.

• Anions and cations can act as acids.
• There are three categories for bases.

• The hydroxide ion, OH-, is found in NaOH and Ca(OH)2, which are the most familiar bases.

• The behavior of acids as donors and bases as acceptors are represented in isolation in these two sets of equations.
• Consider the acid-base reaction when ammonia is dissolved in water.

• Both of these reactions are represented as equilibrium processes.
• The relative extent to which these reactions proceed is an important topic in a later section of this chapter.
• Water can be either an acid or a base, depending on the nature of the solute dissolved in it.

• A sample of pure water is ionized at 25 degrees.

• Concentrations of hydronium ion and hydroxide ion increase with temperature because the process is endothermic.

• The ion product of water is small.

• The autoionization equilibrium for water is established in all solutions.
• Adding an acid or base to water won't change the equilibrium.

• The missing equilibrium concentration can be calculated.

• The autoionization reaction shifts to the left in order to reduce the stress of the increased hydronium ion concentration.

• Under the right conditions, many molecule and ion may gain or lose a protons.

• Specific vocabulary has been developed to describe the concentrations of the ion in a solution in relative terms.

• A logarithmic scale is a common means of expressing quantities, the values of which may span many orders of magnitude.

• When studying certain processes that occur at nonstandard temperatures, this distinction can be important.
• Unless otherwise stated, references to pH values are assumed to be those at standard temperature.

• Figure 14.2 shows the relationships between [H3O+], [OH-], pH, and pOH, and gives values for these properties at standard temperatures for some common substances.

• The concentrations of [H3O+] and OH- are represented by the pH and pOH scales.
• The values of the pH and pOH of some substances are shown in this chart.

• A solution with a pH of -1.07 has hydronium ion concentration.

• When we burn wood or fossil fuels, carbon dioxide is formed.
• Sulfur trioxide is produced by volcanic activity, but it also comes from burning fossil fuels and the process of "roasting" ores of metal sulfides.
• High temperatures make it possible for the nitrogen and oxygen in the air to be combined.

• The problem of acid rain in industrial areas is caused by the release of the products of combustion and smelting into the air without being stripped of sulfur and nitrogen oxides.
• It was responsible for the destruction of forests and freshwater lakes in North America and Europe until the 1980s.
• The statuary and building facades are made of marble and limestone.
• Regulations limiting the amount of sulfur and nitrogen oxides that can be released into the atmosphere by industry and automobiles have reduced the severity of acid damage to both natural and manmade environments in North America and Europe.
• It is a problem in India and China.

• The US Environmental Protection Agency has a website about acid rain.

• Measurement of the pH of a solution is used to assess its acidity.
• The OpenStax book is free and can be used to calculate the pOH of a solution.

• It can be added to a solution to determine the solution's pH.