Problem 99 - Chemistry and Chemical Reactivity

Question

(a) Name two water-soluble compounds containing the \(\mathrm{Cu}^{2+}\) ion. Name two water-insoluble compounds based on the \(\mathrm{Cu}^{2+}\) ion. (b) Name two water-soluble compounds containing the Ba \(^{2+}\) ion. Name two water-insoluble compounds based on the \(\mathrm{Ba}^{2+}\) ion.

Step-by-Step Solution

Answer

Soluble \(\mathrm{Cu}^{2+}\) compounds: \(\mathrm{CuSO_4}\), \(\mathrm{Cu(NO_3)_2}\); Insoluble: \(\mathrm{Cu(OH)_2}\), \(\mathrm{CuCO_3}\). Soluble \(\mathrm{Ba}^{2+}\) compounds: \(\mathrm{BaCl_2}\), \(\mathrm{Ba(NO_3)_2}\); Insoluble: \(\mathrm{BaSO_4}\), \(\mathrm{BaCO_3}\).

Step 1: Identify Water-Soluble Compounds with \(\mathrm{Cu}^{2+}\)

To solve for water-soluble compounds containing the \(\mathrm{Cu}^{2+}\) ion, we look at common copper compounds and their solubility properties. Some examples include copper(II) sulfate, \(\mathrm{CuSO_4}\), which is highly soluble in water, and copper(II) nitrate, \(\mathrm{Cu(NO_3)_2}\), which is also very soluble in water.

Step 2: Identify Water-Insoluble Compounds with \(\mathrm{Cu}^{2+}\)

For water-insoluble compounds with \(\mathrm{Cu}^{2+}\), consider compounds that are known to form precipitates in water. Copper(II) hydroxide, \(\mathrm{Cu(OH)_2}\), is insoluble in water, as is copper(II) carbonate, \(\mathrm{CuCO_3}\).

Step 3: Identify Water-Soluble Compounds with \(\mathrm{Ba}^{2+}\)

For compounds containing the \(\mathrm{Ba}^{2+}\) ion that are water-soluble, barium chloride, \(\mathrm{BaCl_2}\), is a good example, as is barium nitrate, \(\mathrm{Ba(NO_3)_2}\). Both are soluble in water.

Step 4: Identify Water-Insoluble Compounds with \(\mathrm{Ba}^{2+}\)

Water-insoluble compounds containing \(\mathrm{Ba}^{2+}\) generally include those that form precipitates in water. Barium sulfate, \(\mathrm{BaSO_4}\), and barium carbonate, \(\mathrm{BaCO_3}\), are common examples of such insoluble compounds.

Key Concepts

Copper Compounds

Copper compounds are known for their versatility, vibrant color, and different solubility properties. One well-known copper compound is copper(II) sulfate, denoted as \( \mathrm{CuSO_4} \). This compound is highly soluble in water and is often used in agriculture as a fungicide. Another commonly soluble copper compound is copper(II) nitrate, \( \mathrm{Cu(NO_3)_2} \). This compound dissolves easily in water and is utilized in laboratories.

• Copper(II) sulfate, \( \mathrm{CuSO_4} \), dissolves readily, making it useful in various aqueous solutions.
• Copper(II) nitrate, \( \mathrm{Cu(NO_3)_2} \), is another water-soluble copper compound often used in educational demonstrations.

On the other hand, some copper compounds are not water-soluble and form precipitates, which are solid particles that separate from solutions. Copper(II) hydroxide, \( \mathrm{Cu(OH)_2} \), is such an example, often appearing as a blue, gelatinous substance when formed. Similarly, copper(II) carbonate, \( \mathrm{CuCO_3} \), is insoluble and creates solid forms.

Barium Compounds

Barium compounds exhibit distinct properties depending on their solubility in water. Barium chloride, \( \mathrm{BaCl_2} \), is a water-soluble compound commonly used in the purification of brine solutions in the chemical industry. Similarly, barium nitrate, \( \mathrm{Ba(NO_3)_2} \), is soluble in water and has applications in pyrotechnics due to its vivid green flame.

• Barium chloride, \( \mathrm{BaCl_2} \), easily dissolves in water, offering utility in chemical processes.
• Barium nitrate, \( \mathrm{Ba(NO_3)_2} \), is utilized in both research and entertainment industries due to its solubility.

However, not all barium compounds are water-soluble. Some, like barium sulfate, \( \mathrm{BaSO_4} \), are known for their insolubility, making them useful in medical imaging as a contrast agent. Barium carbonate, \( \mathrm{BaCO_3} \), is another commonly encountered insoluble barium compound, often used in ceramics and glass manufacturing due to its ability to form stable solids.

Precipitates

Precipitates are solid forms that appear when certain substances react in a solution and become insoluble. These solid particles settle out of the solution and can often be seen as cloudy suspensions or deposits at the bottom of a container. In chemistry, precipitates are a key way to determine the solubility properties of various compounds.A notable example is when copper(II) hydroxide, \( \mathrm{Cu(OH)_2} \), forms a precipitate upon mixing copper solutions with bases. This results in a distinctive blue solid. Similarly, barium sulfate, \( \mathrm{BaSO_4} \), is a known precipitate that forms when barium and sulfate ions come together in solution. Its formation is often used diagnostically in medical imaging due to its opaque nature, which makes it visible under X-rays.

• Precipitates indicate the formation of an insoluble compound within a solution.
• Copper(II) hydroxide forms a blue precipitate when created from copper solutions.
• Barium sulfate forms a white precipitate, useful in medical settings for enhancing imaging techniques.

Water Solubility

Water solubility refers to the ability of a substance to dissolve in water, creating a homogeneous mixture at a molecular level. The solubility depends on the interaction between water molecules and the ions or molecules of the solute. For ionic compounds, such interactions are influenced by factors such as the lattice energy of the compound and the hydration energy derived from water molecules.In compounds such as copper(II) sulfate and barium chloride, the ionic bonds are overcome by the attraction to water molecules, allowing these compounds to dissolve readily. This is contrasted by compounds like copper(II) carbonate and barium sulfate, which do not dissolve due to their stronger crystalline lattice structures that water cannot break apart.

• Water solubility is crucial for determining how substances interact in natural and industrial processes.
• Soluble substances, such as \( \mathrm{CuSO_4} \) and \( \mathrm{BaCl_2} \), dissolve completely in water, forming clear solutions.
• Insoluble compounds, such as \( \mathrm{CuCO_3} \) and \( \mathrm{BaSO_4} \), often result in the formation of precipitates.