Acids and Bases Properties

10.1 Properties of Acids and Bases

Acid erosion is a growing concern due to modern diets rich in acidic foods like citrus fruits, juices, tomatoes, sour candy, and pop.
Acids, such as citric acid in oranges and limes, and phosphoric and carbonic acids in cola, can prematurely wear away teeth.
To prevent tooth damage, reduce consumption of acidic foods and drinks.
Tooth enamel consists of calcium hydroxylapatite, Ca{10}(PO4)6(OH)2(s), which can be broken down by hydrogen ions in acidic fluids, leading to demineralization.
The demineralization process is represented by the equation: Ca{10}(PO4)6(OH)2(s) + 8H^+(aq) \rightarrow 10Ca^{2+}(aq) + 6HPO4^{2-}(aq) + 2H2O(l).
Brushing teeth immediately after drinking cola (pH 3) may be harmful because tooth enamel is softest then.
Acids have properties in common, including reactivity with certain minerals and low pH.

Acids and bases have been known for centuries; ancient winemakers knew that exposure to air makes wine sour due to the production of ethanoic acid (acetic acid).
The word "acid" comes from the Latin word acidus, meaning sour.
The word "alkali" (another name for bases) comes from the Arabic term al-qilwi, meaning "basic."
Ancient civilizations discovered that wood ashes dissolved in water produced a corrosive mixture and that cooking wood ashes with animal fats or vegetable oils produced an effective cleaner. Wood ashes are rich in potassium carbonate, K2CO3.
Soap is produced today using the same ingredients (a base and fat) in a process called saponification.

Group 1 elements are called “alkali metals” and their oxides form basic solutions.
Group 2 elements are the alkaline earth metals, which also react to form basic solutions.

Empirical understanding of acids and bases existed long before knowledge of their chemical structures.
Acids have a pH less than 7, while bases have a pH greater than 7.
Both acids and bases vary in electrical conductivity.
Acids taste sour, while bases taste bitter (Note: Never taste chemicals in the lab).
Bases feel slippery (Note: Never touch chemicals labeled “corrosive”).
Acids and bases change the colours of acid–base indicators.
Acids neutralize bases, and bases neutralize acids.

Acids react with metals above hydrogen on the activity series to produce hydrogen gas.
For example: Mg(s) + 2HCl(aq) \rightarrow MgCl2(aq) + H2(g).
Acids react with carbonate compounds to produce carbon dioxide: CaCO3(s) + 2HCl(aq) \rightarrow CaCl2(aq) + CO2(g) + H2O(l).

Bases react with carbon dioxide to form carbonates. For example: Ca(OH)2(aq) + CO2(g) \rightarrow CaCO3(s) + H2O(l).
Bases react with oils and fats to produce soap; the slippery feel of bases on skin is due to this reaction.

Many traditional names were used to identify acids and bases; some remain in everyday use (e.g., muriatic acid for hydrochloric acid, caustic soda and lye for sodium hydroxide).

Acids are sometimes represented by the general formula HA(aq), where “H” represents hydrogen and “A” represents the rest of the acid’s formula. The (aq) symbol is added because most acids show their acidic properties only when they are dissolved in water.

Names of acids without oxygen start with the prefix hydro- and end with -ic acid, using the stem of the element or group following hydrogen in the formula.
For example, HCl(aq) is called hydrochloric acid because it contains chlorine.
Examples include hydrofluoric acid (HF(aq), hydrochloric acid (HCl(aq)), and hydroiodic acid (HI(aq).

The name of an acid that contains oxygen is based on the name of its oxyanion; these acids are called oxyacids.
If the oxyanion name ends in -ate, the acid name ends in -ic acid. For example: nitrate ion (NO3^−) becomes nitric acid (HNO3(aq).
If the oxyanion name ends in -ite, the acid name ends in -ous acid. For example: nitrite ion (NO2^−) becomes nitrous acid (HNO2(aq).
All halogens follow this pattern for the names and formulas of their oxyanions.

To name acids, start by identifying whether oxygen is present. If not, use the hydro---ic acid naming convention. If oxygen is present, identify the oxyanion and use the -ate to -ic acid or -ite to -ous acid naming convention.
perate anion becomes peric acid (e.g., perchloric acid)
___ate anion becomes ___ic acid (e.g., chloric acid)
___ite anion becomes ___ous acid (e.g., chlorous acid)
hypoite anion becomes hypoous acid (e.g., hypochlorous acid)

Write the chemical formula of bromic acid.
Step 1. Since the prefix hydro- is not present, bromic acid is an oxyacid.
Step 2. Since the stem of the acid’s name is brom- and the suffix is -ic, the oxyanion is the bromate ion, BrO_3^−.
Step 3. Since the charge of the bromate ion is –1, only one H^+ ion is required to produce a neutral acid molecule.
Step 4. The formula of bromic acid is HBrO_3(aq).

For this course, learn how to name bases that are ionic hydroxides, such as sodium hydroxide, NaOH(aq), and calcium hydroxide, Ca(OH)_2(aq).
The name of the base is the same as the name of the ionic hydroxide.
Hydroxide bases only show their basic properties when they are in solution; because of this, the symbol (aq) is always used in the chemical formula of a base.

Acids taste sour, have a pH less than 7, conduct electricity (to varying degrees), change the colours of acid‒base indicators, and neutralize bases.
Acids react with metals above hydrogen on the activity series.
Acids react with carbonate compounds.
Bases taste bitter, feel slippery, have a pH greater than 7, conduct electricity to some degree, change the colours of acid‒base indicators, and neutralize acids.
Acids that do not have oxygen in the formula are named hydro____ic acid.
The names of acids with oxygen are based on the name of their oxyanion.
The names of bases that are ionic hydroxides are simply the names of the ionic hydroxides.