Write the name from the formula or the formula from the name for each hydrated ionic compound.
a. cobalt(II) phosphate octahydrate
b. BeCl₂•2 H₂O
c. chromium(III) phosphate trihydrate
d. LiNO₂•H₂O

Verified step by step guidance

Identify the cation and its charge: Cobalt(II) indicates a cobalt ion with a +2 charge, written as Co^{2+}.

Identify the anion: Phosphate is PO_4^{3-}.

Determine the formula for the ionic compound: Combine Co^{2+} and PO_4^{3-} to form a neutral compound. The formula is Co_3(PO_4)_2.

Identify the number of water molecules: Octahydrate indicates 8 water molecules, written as \cdot 8H_2O.

Combine the ionic compound and water molecules: The full formula for cobalt(II) phosphate octahydrate is Co_3(PO_4)_2 \cdot 8H_2O.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hydrated Ionic Compounds

Hydrated ionic compounds are salts that incorporate water molecules into their crystalline structure. The water molecules are typically represented in the formula as 'nH2O', where 'n' indicates the number of water molecules associated with each formula unit of the salt. Understanding how to identify and name these compounds is essential for accurately converting between their names and formulas.

Nomenclature of Ionic Compounds

The nomenclature of ionic compounds involves specific rules for naming compounds based on their constituent ions. For hydrated compounds, the name includes the ionic compound's name followed by a prefix indicating the number of water molecules, such as 'mono-', 'di-', 'tri-', etc. In the case of cobalt(II) phosphate octahydrate, 'octa-' signifies the presence of eight water molecules.

Chemical Formulas

Chemical formulas provide a concise way to represent the composition of a compound, indicating the types and numbers of atoms present. For hydrated ionic compounds, the formula includes both the ionic part and the associated water molecules, such as Co3(PO4)2·8H2O for cobalt(II) phosphate octahydrate. Understanding how to derive and interpret these formulas is crucial for chemistry problem-solving.

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