Problem 134 - A Complete Resource Book in Chemistry for JEE Main

Question

Select the correct statement(s): (a) \(\mathrm{BaSO}_{4}\) is soluble in water (b) \(\mathrm{Ba}(\mathrm{OH})_{2}\) is soluble in water (c) \(\mathrm{MgSO}_{4}\) is soluble in water (d) \(\mathrm{CaF}_{2}\) is soluble in water

Step-by-Step Solution

Answer

Statements (b) and (c) are correct.

Step 1: Determine Solubility of BaSO4

Barium sulfate, \( \mathrm{BaSO}_{4} \), is known for being poorly soluble in water. This is a common characteristic of sulfate salts containing heavy metal cations. Thus, \( \mathrm{BaSO}_{4} \) is not soluble in water.

Step 2: Determine Solubility of Ba(OH)2

Barium hydroxide, \( \mathrm{Ba(OH)}_{2} \), is somewhat soluble in water. It dissolves in water to form a solution, which is why it is often used in laboratories. Therefore, \( \mathrm{Ba(OH)}_{2} \) is soluble in water.

Step 3: Determine Solubility of MgSO4

Magnesium sulfate, \( \mathrm{MgSO}_{4} \), is highly soluble in water. This compound, commonly known as Epsom salt, dissolves readily in water, making it useful for various purposes including medicinal ones.

Step 4: Determine Solubility of CaF2

Calcium fluoride, \( \mathrm{CaF}_{2} \), is not particularly soluble in water. It is known for its very low solubility, characteristic of many fluoride salts containing heavier alkaline earth metals.

Key Concepts

Barium Sulfate Solubility

Barium sulfate, denoted as \( \mathrm{BaSO}_4 \), is a compound known for its low solubility in water. Many sulfate salts, especially those containing heavy metals like barium, share this characteristic. This limited solubility is due to the strong ionic bonds within the crystal lattice of \( \mathrm{BaSO}_4 \), which require significant energy to break.

Due to its poor water solubility, \( \mathrm{BaSO}_4 \) finds use in medical imaging. It serves as a contrast agent in X-ray examinations of the digestive system, because it does not dissolve in bodily fluids, thus providing a clear image.

Barium Hydroxide Solubility

Barium hydroxide, represented as \( \mathrm{Ba(OH)_2} \), is considerably more soluble in water than barium sulfate. Upon dissolution, it forms a clear, alkaline solution. This solubility is because hydroxides of alkaline earth metals, particularly starting from calcium down the group, tend to dissolve readily in water.

The solubility of \( \mathrm{Ba(OH)_2} \) is leveraged in industrial and laboratory applications due to its ability to provide a stable, concentrated base solution. It is often used in titrations and as a precursor in the manufacture of various barium compounds.

Magnesium Sulfate Solubility

Magnesium sulfate, or \( \mathrm{MgSO}_4 \), is highly soluble in water. Its high solubility makes it useful as Epsom salt, familiar in household and healthcare contexts for relieving sore muscles and minor sprains through a warm soak.

When \( \mathrm{MgSO}_4 \) dissolves in water, it dissociates completely into magnesium and sulfate ions. This ease of dissolution is attributed to the relatively small ionic charges and sizes, compared to heavier counterparts, facilitating the separation in an aqueous solution.

• Commonly used in bath salts.
• Employed in agriculture to correct magnesium deficiency in crops.

Calcium Fluoride Solubility

Calcium fluoride, expressed as \( \mathrm{CaF}_2 \), is known for having low solubility in water. This comes from the strong lattice energy inherent in fluoride salts paired with heavier alkaline earth metals, making them require more energy for dissolution.

Despite its low solubility, \( \mathrm{CaF}_2 \) is an important compound because it serves as a source of fluoride ions which are beneficial in fortifying dental health. Moreover, it plays a crucial role in the production of hydrofluoric acid and in metallurgical processes.