Question

Write the chemical formula for each of the following \(\mathrm{com}^{-}\) pounds, and indicate the oxidation state of the group \(6 \mathrm{~A}\) element in each: (a) selenous acid, (b) potassium hydrogen sulfite, (c) hydrogen telluride, (d) carbon disulfide, (e) calcium sulfate, (f) cadmium sulfide, (g) zinc telluride.

Short answer

The chemical formulas and oxidation states of the group 6A elements for the given compounds are as follows: (a) Selenous acid: H2SeO3, Se +4; (b) Potassium hydrogen sulfite: KHSO3, S +4; (c) Hydrogen telluride: H2Te, Te -2; (d) Carbon disulfide: CS2, S -2; (e) Calcium sulfate: CaSO4, S +6; (f) Cadmium sulfide: CdS, S -2; and (g) Zinc telluride: ZnTe, Te -2.

Step-by-step solution

(a) Selenous acid

Selenous acid is H2SeO3. The group 6A element is selenium (Se). To find its oxidation state, note that there are two hydrogen atoms (each with an oxidation state of +1) and three oxygen atoms (each with an oxidation state of -2). Let x be the oxidation state of Se. We can write the equation: 2(1) + x + 3(-2) = 0 Solving for x, we find that the oxidation state of selenium in selenous acid is +4.

(b) Potassium hydrogen sulfite

Potassium hydrogen sulfite is KHSO3. The group 6A element is sulfur (S). The oxidation states of potassium, hydrogen, and oxygen are +1, +1, and -2, respectively. Let x be the oxidation state of S. We can write the equation: 1 + 1 + x + 3(-2) = 0 Solving for x, we find that the oxidation state of sulfur in potassium hydrogen sulfite is +4.

(c) Hydrogen telluride

Hydrogen telluride is H2Te. The group 6A element is tellurium (Te). There are two hydrogen atoms (each with an oxidation state of +1). Let x be the oxidation state of Te. We can write the equation: 2(1) + x = 0 Solving for x, we find that the oxidation state of tellurium in hydrogen telluride is -2.

(d) Carbon disulfide

Carbon disulfide is CS2. The group 6A element is sulfur (S). There are two sulfur atoms and one carbon atom (oxidation state of +4). Let x be the oxidation state of S. We can write the equation: 4 + 2x = 0 Solving for x, we find that the oxidation state of sulfur in carbon disulfide is -2.

(e) Calcium sulfate

Calcium sulfate is CaSO4. The group 6A element is sulfur (S). The oxidation states of calcium and oxygen are +2 and -2, respectively. Let x be the oxidation state of S. We can write the equation: 2 + x + 4(-2) = 0 Solving for x, we find that the oxidation state of sulfur in calcium sulfate is +6.

(f) Cadmium sulfide

Cadmium sulfide is CdS. The group 6A element is sulfur (S). The oxidation state of cadmium is +2. Let x be the oxidation state of S. We can write the equation: 2 + x = 0 Solving for x, we find that the oxidation state of sulfur in cadmium sulfide is -2.

(g) Zinc telluride

Zinc telluride is ZnTe. The group 6A element is tellurium (Te). The oxidation state of zinc is +2. Let x be the oxidation state of Te. We can write the equation: 2 + x = 0 Solving for x, we find that the oxidation state of tellurium in zinc telluride is -2.

Key concepts

Chemical Formula

Understanding the chemical formula of a compound is crucial for studying its properties and behaviors in reactions. A chemical formula represents the types and numbers of atoms present in a substance. For instance, the chemical formula for water, H₂O, indicates that each molecule consists of two hydrogen atoms bonded to one oxygen atom.

When writing the chemical formula for more complex compounds, such as the ones listed in the exercise, it is important to know the valencies or charge states of the elements involved. This knowledge allows us to correctly balance the formula, ensuring that the compound is electrically neutral. As an example, calcium sulfate's formula is CaSO₄ because calcium typically has a +2 charge and sulfate (SO₄) has a -2 charge, making the Ca:SO₄ ratio 1:1 to achieve neutrality.

Oxidation State Calculation

The oxidation state of an element in a compound refers to the hypothetical charge that an atom would have if all bonds to atoms of different elements were completely ionic. Calculating oxidation states is a fundamental skill in chemistry as it helps predict the reactivity and properties of a molecule.

To calculate the oxidation state, follow these general rules: The oxidation state of a pure element is always zero. The sum of the oxidation states in a neutral molecule must be zero, and in an ion, it must equal the charge of the ion. Group 1 elements have an oxidation state of +1, Group 2 elements have +2, oxygen usually has -2 (except in peroxides or when bonded to fluorine), and hydrogen has +1 when bonded to nonmetals and -1 when bonded to metals.

Using these rules, you can set up an algebraic equation where the sum of the oxidation states equals the charge of the molecule or ion. Solve for the unknown oxidation state to find the answer.

Group 6A Elements

Group 6A, also known as Group 16 in the periodic table, includes oxygen, sulfur, selenium, tellurium, and polonium. These elements are commonly referred to as the chalcogens. They play significant roles in biological and geological processes and have notable differences in their oxidation states.

Oxygen, being the most electronegative in the group, commonly exhibits an oxidation state of -2. Sulfur, selenium, and tellurium show more variability, ranging from -2 to +6, depending on the other atoms they're bonded to and the compound's overall structure. In the compounds from the exercise, we see sulfur and selenium having oxidation states of +4 or +6 and tellurium with -2, showcasing this variability.

It's important to note that these oxidation states directly influence the chemical reactivity and bonding patterns of the compounds containing these elements, making their determination essential for understanding chemical reactions and mechanisms.