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4.7: Applications and Solubility of Ionic Compounds

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  • Learning Objectives

    • Read the solubility of an ionic compound by using a provided table.
    • Use the abbreviations (aq) and (s) appropriately.
    • Realize soluble compounds will form homogeneous mixtures in water.
    • Realize insoluble compounds will form heterogeneous mixtures in water.
    • Know applications of the compounds contained on this page.
    • Be able to match polyatomic names with their uses/properties shown in the chart of this section.

    Determining Ionic Solubility

    Inorganic compounds can be dissolved to sanitize drinking water. Water distributors may use a variety of methods to disinfect water. Chemical disinfection of water typically involves adding a form of chlorine. This can be done by either bubbling chlorine gas into a system or adding soluble inorganic chlorinated compounds. Using chlorine gas involves a great bit of skill due to its toxic nature. This yellow-green gas is denser than air and has previously been used as a chemical weapon. On the other hand, soluble chlorinated compounds are more stable and less toxic to handle. Regardless of its form, chlorine can be quite corrosive.

    Figure \(\PageIndex{1}\): Chlorine gas in a Florence flask and concentrated liquid solutions for use in swimming pool. Image used with permission (CC BY-SA 4.0; gas flask - Larenmclane and pool chlorine - Maksym Kozlenko)

    In order to kill bacteria and viruses, the chlorinated compound must be soluble in water. Chlorine-based ions that become soluble can deactivate most all microorganisms except protozoans (examples would be giardia and cryptosporidium). In determining whether an inorganic chlorine compound will be soluble, chemists refer to a solubility table. The table below shows the solubilities of various compounds, in water, at a pressure of 1 atm and at room temperature (~293 K). Any box that reads "aq" results in an aqueous product in which no solid remains, while "s" indicated that the compound will not dissolve in water. Boxes marked "d" mean that the compound decomposes on reacts with water.

    Solubility can be altered by manipulating temperature. Typically, many insoluble compounds can be dissolved at higher temperatures; however, this trend does not apply to every compound. For example, for Flint River residents, boiling their drinking water increased the solubility of the lead compounds that were already present. This action made the lead more concentrated and produced higher ppb levels. Please do not memorize the solubility table for this class. A chart will always be accessible for tests and quizzes.

    Table \(\PageIndex{1}\): Solubility chart of ionic compounds in water (s = solid, aq = aqueous/soluble, and d= decomposes)
    Ion acetate carbonate chlorate chloride fluoride hydroxide nitrate nitrite phosphate sulfate sulfide sulfite
    aluminum s s aq aq s s aq s aq d d
    ammonium aq aq aq aq aq aq aq aq aq aq aq aq
    barium aq s aq aq s aq aq aq s s s s
    calcium aq s aq aq s s aq aq s s d s
    cobalt II aq s aq aq s s aq s aq s s
    iron III s s s aq aq s aq s aq s s
    copper II aq s aq aq s s aq s aq s s
    lead II aq s aq s s s aq aq s s s s
    lithium aq aq aq aq aq aq aq aq aq aq aq aq
    magnesium aq s aq aq s s aq aq s aq ------- aq
    nickel II aq s aq aq aq s aq s aq s s
    potassium aq aq aq aq aq aq aq aq aq aq aq aq
    silver s s aq s aq s aq s s s s s
    sodium aq aq aq aq aq aq aq aq aq aq aq aq
    zinc aq s aq aq aq s aq s aq s s

    Encountering Ionics in the Home

    There are many real-world applications of ionic compounds. For example, sodium chloride (table salt) is used to season food. Consuming large amounts of sodium ion (regardless if it is from sodium chloride, sodium glutamate, or sodium benzoate) can lead to cardiovascular and kidney problems. The American Heart Association recommends that individuals limit their sodium intake to less than 2300 mg per day. Watch the video below to obtain more information about sodium:

    Video \(\PageIndex{1}\): Where do Americans get most of their sodium? According to a study published in the journal Circulation, restaurant and processed foods accounted for nearly 71 percent of consumer’s dietary sodium in a study of three U.S. regions.

    People who still want to season their food without sodium can opt to use potassium chloride, a table salt substitute. Unfortunately, this compound can taste extremely bitter. For this reason, some table salt substitutes will contain a mixture of both of these compounds.

    Another ionic compound that can be commonly found is calcium carbonate. This compound is also known as chalk and is contained in antacids like Tums and Rolaids. The carbonate portion of this formula helps to neutralize excess stomach acid to help soothe the stomach. When purchasing these over the counter medications, remember to buy generic forms of these products.

    antacids for oer.jpg
    Figure \(\PageIndex{2}\): Bottle of Antacid tablets. Image used with permission (CC BY-SA 3.0; Midnightcomm).

    These type of antacids are quick acting and should be used for short-term stomach problems. If you experience chronic reflux or upset stomach, a health care professional would suggest a different type of medication (like Nexium, Zantac, or Prilosec) that does not neutralize excess stomach acid. Instead, these three medications deactiviate enzymes that produce the excess stomach acid.

    Antacids that contain carbonates and bicarbonates will produce carbon dioxide gas inside the body. Unless an antigas ingredient is added in these products, then the patient will feel quite gaseous. Other side effects that can occur from taking these medications would be diarrhea (if magnesium is present) or constipation (if aluminum is present).

    Two common compounds used to sanitize are ammonium hydroxide and sodium hypochlorite. Ammonia has a pungent odor and a basic pH (value greater than 7.0). Derivatives of ammonia are used as fertilizers and smelling salts (stimulant). When working with ammonia-based compounds, individuals need to be aware of its corrosive nature. In addition, this compound can be extremely deadly to people who have lung impairments like asthma or COPD.

    smelling salts.jpg
    Figure \(\PageIndex{3}\): Generic smelling salts can be used to revive a person who has fainted. Image taken from:

    The common name for sodium hypochlorite is bleach. It is less volatile than ammonia but still has a distinct smell. This chemical is used to remove stains from clothing and can be used to disinfect water. Both ammonia and bleach are effective in killing most germs. However, these two chemicals should never be combined to make a new household cleaner. The resulting product of this reaction would be chlorine gas.

    Real-world applications of specific polyatomic ions

    sulfites in wine.jpg
    Figure \(\PageIndex{4}\): This red wine contains sulfite preservatives. Image made by Elizabeth R. Gordon

    Ionic compounds that contain certain polyatomics can have a variety of applications. The table below gives a sample of where you might encounter polyatomic ions. For this class, it is important to match a polyatomic with its application or stated property.

    Polyatomic Ion Uses/Facts
    Carbonates and Bicarbonates CO32-/HCO3- Short-term antacids, act as bases (high pH)
    Nitrates NO3- Fertilizers, explosives, and preserved meats (mutagen and probable carcinogen)(a suspected cause of migraines)
    Nitrites NO2- Preservative for meats (mutagen and probable carcinogen)(a suspected cause of migraines)
    Phosphates PO43- Fertilizers (gives the green color to plants, if not present in sufficient amounts plants will die)
    Alkali Hydroxides OH- Very corrosive bases, found in dry batteries, soaps, Drano, and oven cleaner
    Sulfites SO32- Preservative found in dried fruit and red wine (possible allergen)
    Cyanides CN- Poison used in Tylenol Murders and Jim Jones cases. Smells like almonds

    Click on the video below to watch a short production of how cyanide affected the United States in 1982. After viewing, note how drug packaging changed following this event.

    Figure \(\PageIndex{5}\): Tylenol 1982 Murders - PR Strategy

    Exercise \(\PageIndex{1}\)

    1. When a compound dissolves in water, what abbreviation do you place beside the chemical formula?
    2. Which compounds (when dissolved in individual containers) would produce heterogeneous mixtures in water: silver sulfate, iron III chlorate, lithium hydroxide, magnesium phosphate, or lead II nitrate.
    3. Which compounds could be used to preserve meats: KNO3, KOH, or K2CO3?
    4. Write all the chemical formulas for the aqueous compounds in #2.
    5. Which compound in question c could be used as an antacid?
    Answer a

    Place the abbreviation (aq) to the right of the chemical formula to indicate compound is water soluble.

    Answer b

    Iron III chlorate and magnesium phosphate are both insoluble compounds. These ionic compounds would form heterogeneous mixtures with water.

    Answer c

    KNO3 contains a nitrate which could be used as a chemical preservative.

    Answer d

    LiOH(aq), Al2(SO4)3 (aq), and Pb(NO3)2(aq) are all water soluble.

    Answer e

    K2CO3 contains a carbonate which can safely neutralize excess stomach acid.


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