Problem 132 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following sulphates are soluble in water? (a) \(\mathrm{PbSO}_{4}\) (b) \(\mathrm{CuSO}_{4}\) (c) \(\mathrm{BaSO}_{4}\) (D) \(\mathrm{Ag}_{2} \mathrm{SO}_{4}\)

Step-by-Step Solution

Answer

(b) \(\mathrm{CuSO}_{4}\) is soluble in water.

Step 1: Identify Common Solubility Rules for Sulphates

Sulphates are typically soluble in water, but there are exceptions including \(\text{PbSO}_4\), \(\text{BaSO}_4\), and \(\text{Ag}_2\text{SO}_4\). These are known as insoluble sulphates.

Step 2: Examine the Given Compounds

Review each compound against the common solubility rules:- \(\mathrm{PbSO}_4\) is insoluble.- \(\mathrm{CuSO}_4\) is soluble.- \(\mathrm{BaSO}_4\) is insoluble.- \(\mathrm{Ag}_2\mathrm{SO}_4\) is slightly soluble, often treated as insoluble in academic settings.

Step 3: Determine the Soluble Sulphate

According to the rules and examination, \(\mathrm{CuSO}_4\) is the only sulphate among the options that is soluble in water.

Key Concepts

Insoluble Sulphates

When discussing solubility, certain sulphates are often highlighted because they defy the general rule of sulphate solubility. Usually, sulphates are seen as soluble in water. However, some specific compounds buck this trend, making them key exceptions to remember.
\( \text{PbSO}_4 \), \( \text{BaSO}_4 \), and \( \text{Ag}_2\text{SO}_4 \) are examples of these oddities:

• Lead Sulphate (\( \text{PbSO}_4 \)): A common example in solubility discussions, as it does not dissolve in water.
• Barium Sulphate (\( \text{BaSO}_4 \)): Widely used in medical imaging because of its insolubility, making it safe for such applications.
• Silver Sulphate (\( \text{Ag}_2\text{SO}_4 \)): Though it's slightly soluble, it’s often categorized as insoluble in educational settings.

Understanding these exceptions helps when predicting the behavior of sulphates in chemical reactions and experimental setups. It allows students to anticipate which compounds will interact with solvents and which will remain unchanged.

Soluble Compounds

In contrast to insoluble sulphates, most common sulphates dissolve well in water. Recognizing these typical soluble compounds is crucial in chemistry, particularly in reactions and solutions.

• Copper(II) Sulphate (\( \text{CuSO}_4 \)): Well known for its vibrant blue color when hydrated, making it a popular choice for experiments and demonstrations in chemistry labs.

Generally, the solubility of a compound in water dictates how it will participate in chemical processes. Soluble compounds dissociate into ions, allowing them to engage readily in reactions. Knowing the solubility of a compound can thus serve as a guide when predicting the outcomes of chemical interactions. For example, the solubility of \( \text{CuSO}_4 \) allows it to easily interact with other ions in a solution, whereas \( \text{PbSO}_4 \) does not.

Chemical Examination

Chemical examination is vital for determining the solubility of compounds. In practice, this involves looking at established chemical rules and performing tests that reveal how compounds behave in solvents.
When analyzing compounds:

• Use Solubility Rules: These are guidelines developed from empirical data that can predict whether a compound will dissolve in water. Recognizing patterns, such as the solubility of most sulphates, aids in anticipating chemical behavior.
• Conduct Experiments: Testing compounds in water and observing changes, like dissociation into ions or lack thereof, complements theoretical understanding.

This combination of rules and hands-on testing enhances a chemist's ability to accurately determine a compound's solubility. Such evaluations are essential not just for academic exercises, but for practical applications in product formulations and various scientific fields.