Problem 32 - Chemistry The Central Science

Question

Write the chemical formula for each of the following compounds, and indicate the oxidation state of the halogen or noble-gas atom in each: (a) chlorate ion, (b) hydroiodic acid, (c) iodine trichloride, (d) sodium hypochlorite, (e) perchloric acid, (f) xenon tetrafluoride.

Step-by-Step Solution

Answer

(a) The chlorate ion has the formula \(ClO_3^-\) and chlorine's oxidation state is +5. (b) Hydroiodic acid has the formula HI and iodine's oxidation state is -1. (c) Iodine trichloride has the formula ICl3 and iodine's oxidation state is +3. (d) Sodium hypochlorite has the formula NaClO and chlorine's oxidation state is +1. (e) Perchloric acid has the formula HClO4 and chlorine's oxidation state is +7. (f) Xenon tetrafluoride has the formula XeF4 and xenon's oxidation state is +4.

Step 1: (a) Chlorate ion

The chlorate ion consists of one chlorine atom and three oxygen atoms, with an overall negative charge. Its chemical formula is \(ClO_3^-\). To find the oxidation state of chlorine, we use the fact that the sum of oxidation states in a compound must equal its overall charge, which is -1 in this case. Since oxygen has an oxidation state of -2, we get the following equation: 1 * (oxidation state of Cl) + 3 * (-2) = -1 Solving for the oxidation state of chlorine: Oxidation state of Cl = +5 The chlorate ion has the formula \(ClO_3^-\) and chlorine's oxidation state is +5.

Step 2: (b) Hydroiodic acid

Hydroiodic acid is a binary acid containing hydrogen and iodine. Its chemical formula is HI. In this case, the hydrogen atom has an oxidation state of +1. So, the oxidation state of iodine is -1. Hydroiodic acid has the formula HI and iodine's oxidation state is -1.

Step 3: (c) Iodine trichloride

Iodine trichloride consists of one iodine atom and three chlorine atoms. Its chemical formula is ICl3. The oxidation state of chlorine is -1. Therefore, the oxidation state of iodine is +3 to balance the overall charge of the compound: 1 * (oxidation state of I) + 3 * (-1) = 0 Iodine trichloride has the formula ICl3 and iodine's oxidation state is +3.

Step 4: (d) Sodium hypochlorite

Sodium hypochlorite is a compound consisting of sodium, oxygen, and chlorine. Its chemical formula is NaClO. The oxidation state of sodium is +1 and oxygen is -2. To balance the overall charge of the compound, the oxidation state of chlorine is: 1 * +1 + 1 * (oxidation state of Cl) + 1 * (-2) = 0 Oxidation state of Cl = +1 Sodium hypochlorite has the formula NaClO and chlorine's oxidation state is +1.

Step 5: (e) Perchloric acid

Perchloric acid is an oxyacid with chlorine and four oxygen atoms. Its chemical formula is HClO4. The oxidation state of hydrogen is +1, and oxygen is -2. To balance the overall charge of the compound, the oxidation state of chlorine is: 1 * +1 + 1 * (oxidation state of Cl) + 4 * (-2) = 0 Oxidation state of Cl = +7 Perchloric acid has the formula HClO4 and chlorine's oxidation state is +7.

Step 6: (f) Xenon tetrafluoride

Xenon tetrafluoride consists of one xenon atom and four fluorine atoms. Its chemical formula is XeF4. The oxidation state of fluorine is -1. To balance the overall charge of the compound, the oxidation state of xenon is: 1 * (oxidation state of Xe) + 4 * (-1) = 0 Oxidation state of Xe = +4 Xenon tetrafluoride has the formula XeF4 and xenon's oxidation state is +4.

Key Concepts

Oxidation States

Oxidation states, also known as oxidation numbers, are fundamental concepts in chemistry. They help predict the chemical formula of compounds and balance chemical equations. An oxidation state represents the degree of electron loss or gain by an element in a compound. For instance, each oxygen atom in compounds typically has an oxidation state of -2. This is because oxygen tends to gain electrons. Understanding oxidation states involves remembering a few key rules:

• In neutral compounds, the sum of all oxidation states must be zero.
• In ions, the sum of oxidation states should match the overall charge of the ion.
• The oxidation state of any element in its standard state is 0.

Consider sodium hypochlorite, with the formula NaClO, where sodium has an oxidation state of +1, and oxygen has -2. To find the chlorine's oxidation state, you assume the total is zero: +1 + (oxidation state of Cl) - 2 = 0, leading to chlorine having an oxidation state of +1. For more complex molecules, such as perchloric acid (HClO₄), calculating oxidation states involves similar arithmetic, ensuring that the total matches the charge of the compound, which in this case is neutral (0). Chlorine in HClO₄ exhibits an oxidation state of +7, balancing hydrogen's +1 and oxygen's -2 contributions.

Halogen Compounds

Halogens, which include elements like chlorine, iodine, and fluorine, are known for forming a wide variety of compounds, often through the gain of electrons to form negative ions. These elements are located in Group 17 of the periodic table and have seven electrons in their outermost shell, making them highly reactive. Halogen compounds are crucial in many industrial and biological processes. Their unique ability to form bonds with both metals and non-metals allows them to create diverse molecules, including salts and acids. Here are a few examples:

• Chlorate ion (ClO₃⁻): In this ion, chlorine forms a compound with oxygen. Chlorine's oxidation state is +5.
• Hydroiodic acid (HI): This is a simple binary compound composed of hydrogen and iodine, where iodine has an oxidation state of -1.
• Iodine trichloride (ICl₃): This compound involves iodine and chlorine, with iodine's oxidation state balanced at +3 due to chlorine's -1 oxidation state.

These compounds illustrate the versatility of halogens in forming complex structures by bonding with various elements. Each halogen's chemical nature influences these bonds and their subsequent properties.

Chemical Nomenclature

Chemical nomenclature refers to the systematic naming of chemical compounds based on established rules and guidelines. It allows scientists and chemists to communicate unambiguously about compounds and their structures. The International Union of Pure and Applied Chemistry (IUPAC) provides standard rules for these names. There are different types of chemical nomenclature systems:

• Binary Compounds: These include compounds with two different elements and are often named using the metal's name first, followed by the non-metal with an "-ide" suffix. Example: sodium chloride ( NaCl).
• Oxyacids: These are acids containing oxygen. Their names usually end in "-ic" or "-ous" depending on the oxidation state of the central atom. Perchloric acid (HClO₄) is an example, where chlorine is the central atom.
• Polyatomic Ions: These are ions consisting of multiple atoms. Their names are often retained in both the compound's name and chemical formula, such as the chlorate ion ( ClO₃⁻).

Understanding chemical nomenclature bridges the gap between the chemical formula and its verbal description, which is essential for analyzing and interpreting chemical literature. Being familiar with compound names and their structures helps further explore their interactions and applications in various contexts.