In the pyroxene kanoite, the formula unit has two SiO3^2- units and is balanced by manganese and

Name: Problem 18, Chapter 24: Chemistry A Molecular Approach
Uploaded: 2020-03-21T15:38:42-08:00
Duration: 2 min 6 s
Channel: Ahmed Ali
Description: In the pyroxene kanoite, the formula unit has two SiO3^2- units and is balanced by manganese and magnesium ions. Determine the formula unit of kanoite. Assume that the oxidation state of Mn is +2 .

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In the pyroxene kanoite, the formula unit has two SiO3^2-...

In the pyroxene kanoite, the formula unit has two $\mathrm{SiO}_{3}^{2-}$ units and is balanced by manganese and magnesium ions. Determine the formula unit of kanoite. Assume that the oxidation state of Mn is +2 .

Key Concepts

Pyroxene Group Minerals

Pyroxenes are a group of silicate minerals characterized by a chain-like arrangement of SiO3 tetrahedra. Their general formula often involves two silicate units combined with metal cations, such as magnesium and manganese. Recognizing the typical arrangement and composition of pyroxenes is crucial when determining the formula unit of a specific member of this group.

Silicate Mineral Structure

Silicate minerals are built from silicon-oxygen tetrahedra, and many, including pyroxenes, feature these tetrahedra arranged in chains or other configurations. The presence of SiO3 units indicates a chain silicate structure, where each silicon atom is tetrahedrally coordinated by oxygen atoms. Understanding this structure is key to interpreting the chemical formula and physical properties of the mineral.

Formula Unit

A formula unit is the simplest repeating unit of an ionic compound that represents the entire structure with the correct stoichiometric ratios of all ions. For minerals, identifying the formula unit involves combining the constituent anions and cations in a way that reflects the true proportions and yields an electrically neutral entity. This concept is central to formulating the overall chemical formula of a mineral like kanoite.

Charge Balance in Chemical Formulas

Charge balance is the principle that the overall charge of a stable compound must be zero. In ionic compounds, the total positive charge contributed by the cations must exactly counterbalance the total negative charge of the anions. This concept is essential when deducing the formula unit of a mineral because it allows one to determine the necessary amounts of different ions so that the sum of their charges yields a neutral compound.

Oxidation States

The oxidation state of an element in a compound reflects the degree of oxidation of an atom and is critical in determining how atoms combine. Knowing the oxidation state of manganese as +2, for instance, helps in calculating how many manganese ions are needed to balance anionic groups within the compound. This concept is important for ensuring the proper distribution of positive and negative charges in the overall formula.

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