Problem 72 - Chemistry and Chemical Reactivity

Question

(a) Name and give formulas for two water-soluble compounds containing the \(\mathrm{Cu}^{2+}\) ion. Name two waterinsoluble compounds containing the \(\mathrm{Cu}^{2+}\) ion. (b) Name and give formulas for two water-soluble compounds containing the \(\mathrm{Ba}^{2+}\) ion. Name two waterinsoluble compounds containing the \(\mathrm{Ba}^{2+}\) ion.

Step-by-Step Solution

Answer

CuSO_4 and Cu(NO_3)_2 are soluble; CuCO_3 and Cu(OH)_2 are insoluble. Ba(NO_3)_2 and BaCl_2 are soluble; BaSO_4 and BaCO_3 are insoluble.

Step 1: Identify common water-soluble compounds of Cu^{2+}

Compounds containing Cu^{2+} that are commonly water-soluble include Copper (II) sulfate, CuSO_4, and Copper (II) nitrate, Cu(NO_3)_2.

Step 2: Identify common water-insoluble compounds of Cu^{2+}

Copper (II) carbonate, CuCO_3, and Copper (II) hydroxide, Cu(OH)_2, are examples of water-insoluble compounds with Cu^{2+}.

Step 3: Identify common water-soluble compounds of Ba^{2+}

For Ba^{2+}, compounds like Barium nitrate, Ba(NO_3)_2, and Barium chloride, BaCl_2, are typically water-soluble.

Step 4: Identify common water-insoluble compounds of Ba^{2+}

Barium sulfate, BaSO_4, and Barium carbonate, BaCO_3, are examples of water-insoluble compounds containing the Ba^{2+} ion.

Key Concepts

Solubility Rules

Solubility rules help us understand if a compound will dissolve in water. These rules are essential for predicting the behavior of ionic compounds when mixed with water.

Key solubility rules include:

• Nitrates (\( ext{NO}_3^- \)) and acetates (\( ext{CH}_3 ext{COO}^- \)) are generally soluble in water.
• Sulfates (\( ext{SO}_4^{2-} \)) are usually soluble, but can be insoluble when combined with ions like \( ext{Ba}^{2+} \).
• Hydroxides (\( ext{OH}^- \)) and carbonates (\( ext{CO}_3^{2-} \)) are often insoluble except with alkali metals.

For example, Copper (II) sulfate (\( ext{CuSO}_4 \)) is water-soluble due to the sulfate ion's general solubility, while Copper (II) hydroxide (\( ext{Cu(OH)}_2 \)) is not, aligning with the rule for insoluble hydroxides.

Chemical Formulas

Chemical formulas represent the elements and the number of atoms in a compound. Knowing how to read and write these formulas is crucial in chemistry.

For instance:

• Copper (II) sulfate is represented as \( ext{CuSO}_4 \), showing it contains copper ions and sulfate ions.
• Barium nitrate is \( ext{Ba(NO}_3)_2 \), indicating one barium ion and two nitrate ions.

Formulas are written using elemental symbols and subscripts. Each subscript denotes the number of atoms of each element in the molecule. Understanding them allows for predicting compounds' reactivity and properties.

Ionic Compounds

Ionic compounds are formed when positive and negative ions attract each other. This type of bonding is key to forming many compounds we encounter.

Characteristics of ionic compounds include:

• High melting and boiling points due to strong ionic bonds.
• Solubility in water varies, governed by solubility rules.
• They conduct electricity when dissolved in water because ions are free to move.

Consider the compound Copper (II) nitrate \( ext{Cu(NO}_3)_2 \): copper ions (\( ext{Cu}^{2+} \)) bond with nitrate ions (\( ext{NO}_3^- \)), creating a soluble ionic compound. Barium sulfate \( ext{BaSO}_4 \), on the other hand, is an example of a water-insoluble ionic compound.