Question

Determine the ratio of cations to anions in each. a. potassium chloride, a salt substitute b. calcium fluoride, used in the steel industry c. calcium oxide, used to remove sulfur dioxide from power-plant exhaust d. strontium chloride, used in fireworks

Short answer

The ratio of cations to anions for the given compounds are: a. Potassium Chloride (KCl): 1:1 b. Calcium Fluoride (CaF2): 1:2 c. Calcium Oxide (CaO): 1:1 d. Strontium Chloride (SrCl2): 1:2

Step-by-step solution

a. Potassium Chloride (KCl)- a salt substitute

To find the ratio of cations to anions in potassium chloride, we need to know the charges of potassium (K) and chlorine (Cl). Potassium has a charge of +1, since it is in group 1 of the periodic table, and chlorine has a charge of -1, being in group 17 (halogens). Therefore, the ratio of cations (K) to anions (Cl) in potassium chloride is 1:1.

b. Calcium Fluoride (CaF2) - used in the steel industry

Calcium has a charge of +2, being in group 2 of the periodic table. Fluorine, a halogen in group 17, has a charge of -1. In calcium fluoride, there are two fluorine atoms, resulting in a total charge of -2. Hence, the ratio of cations (Ca) to anions (F) in calcium fluoride is 1:2.

c. Calcium Oxide (CaO) - used to remove sulfur dioxide from power-plant exhaust

Calcium has a charge of +2 and oxygen has a charge of -2, being a member of the chalcogens (group 16). Thus, the ratio of cations (Ca) to anions (O) in calcium oxide is 1:1 because the charges cancel each other out.

d. Strontium Chloride (SrCl2) - used in fireworks

Strontium has a charge of +2, being in group 2 of the periodic table. Chlorine has a charge of -1 and as there are two chlorine atoms in strontium chloride, the total negative charge is -2. Therefore, the ratio of cations (Sr) to anions (Cl) in strontium chloride is 1:2.

Key concepts

Cations and Anions

Understanding the relationship between cations and anions is fundamental in chemistry. Cations are positively charged ions, while anions are negatively charged. During the formation of an ionic compound, these ions come together to form a neutral compound. The ratio of cations to anions depends on the charges of each ion. For example, in potassium chloride (KCl), potassium (K+) is the cation with a +1 charge, and chloride (Cl-) is the anion with a -1 charge. The resulting compound is neutral, as the charges balance each other in a 1:1 ratio.

When a metal from Group 1 of the periodic table, such as potassium, reacts with a non-metal from Group 17, such as chlorine, they form a salt where the number of cations equals the number of anions. This simplistic scenario shows the beauty of nature's charge balance.

Chemical Formula

A chemical formula represents the composition of a substance using symbols and numbers. The symbols are taken from the periodic table and represent the elements present, while the numbers (subscripts) show the ratio of atoms. For instance, calcium fluoride is denoted by the chemical formula CaF2. This indicates that one calcium (Ca) ion combines with two fluoride (F-) ions to form the compound.

Reading Chemical Formulas

Each subscript in a chemical formula is essentially an instruction for the ratio of each ion in the compound. If there is no subscript, it implies a quantity of one. Through the chemical formula, one can deduce the fixed ratio of atoms, which allows for the prediction of the ratios of cations to anions in the compound; a crucial skill in both academic and practical chemistry settings.

Periodic Table Charges

The periodic table is not just a display of the elements; it's a roadmap of their properties, including their typical charges. Elements are grouped together based on similar properties, including their ability to form ions with characteristic charges. For example, Group 1 elements typically form cations with a +1 charge, while Group 2 elements form cations with a +2 charge.

An understanding of these typical charges is vital when predicting the formulas of compounds. For instance, strontium, a Group 2 element, will likely form Sr2+ cations while chlorine, a Group 17 element, forms Cl- anions. This periodic table knowledge is invaluable in predicting that strontium chloride will have a ratio of one Sr2+ cation to two Cl- anions, reflected in its chemical formula SrCl2.

Chemistry in Industry

The applications of ionic compounds in industry are vast and essential. For example, calcium fluoride (CaF2) is crucial in the steel industry, where it helps to lower the melting point of raw materials in the blast furnace, aiding the removal of impurities.

• Role in the Steel Industry: Calcium fluoride is used as a flux.
• Construction: Calcium oxide (CaO) is integral to making cement and mortar.
• Environmental Control: Additionally, calcium oxide is employed in power plants to remove sulfur dioxide from exhaust gases, showcasing the industry's reliance on chemical properties of ionic compounds to address environmental concerns.
• Entertainment: Strontium chloride (SrCl2), on the other hand, adds red color to fireworks, illustrating how chemical knowledge translates into spectacular visual displays.

Understanding the ratios of ions in these compounds ensures their effective and safe use in these varied industrial applications.