The silicate anion in the mineral kinoite is represented by the following structure. The mineral also contains Ca2+ ions, Cu2+ ions, and water molecules in a 1:1:1 ratio. What are the formula and charge of the silicate anion, and what is the complete formula for the mineral? (LO 22.11) (a) Si3O10^8-; Ca2Cu2Si3O10 · 2 H2O (b) Si3O8^10-; Ca3Cu2Si3O8 · 2 H2O (c) Si3O4^4-; CaCuSi3O8 · H2O (d) Si3O12^12-; Ca3Cu3Si3O12 · 3 H2O

Verified step by step guidance

1. Step 1: Identify the silicate anion structure. The problem states that the silicate anion is part of the mineral kinoite. The silicate anion is typically represented as SiO_x^(y-), where x and y need to be determined based on the options provided.
2. Step 2: Analyze the charge balance. The mineral contains Ca^{2+}, Cu^{2+}, and water molecules in a 1:1:1 ratio. This implies that the total positive charge from the cations must balance the negative charge of the silicate anion.
3. Step 3: Evaluate each option for the silicate anion formula and charge. For each option, calculate the total negative charge of the silicate anion and see if it balances with the total positive charge from the cations (Ca^{2+} and Cu^{2+}).
4. Step 4: Determine the complete formula for the mineral. Once the correct silicate anion is identified, use the 1:1:1 ratio of Ca^{2+}, Cu^{2+}, and water molecules to construct the complete formula of the mineral, ensuring charge neutrality.
5. Step 5: Verify the stoichiometry of water molecules. Check that the number of water molecules in the complete formula matches the stoichiometry given in the options, ensuring the correct formula is selected.

Key Concepts

Silicate Anions

Silicate anions are polyatomic ions composed of silicon and oxygen, typically represented as SiO4 units. The charge and structure of these anions can vary, influencing the overall formula of silicate minerals. Understanding the common silicate structures, such as tetrahedral arrangements, is crucial for determining the formula of minerals containing silicate anions.

Ionic Compounds and Their Formulas

Ionic compounds consist of positively charged cations and negatively charged anions, which combine in ratios that balance their charges. The formula of an ionic compound reflects the simplest whole-number ratio of these ions. In the case of minerals, the presence of additional components like water molecules must also be considered when writing the complete formula.

Hydration in Minerals

Hydration refers to the incorporation of water molecules into the structure of a mineral, which can affect its stability and properties. The number of water molecules associated with a mineral is often indicated in its formula, typically as a dot followed by the number of water molecules. Understanding how hydration influences mineral composition is essential for accurately determining the complete formula of a mineral.