Problem 78 - A Complete Resource Book in Chemistry for JEE Main

Question

Mark the correct statement. (a) V group basic radicals precipitate as carbonates (b) IV group basic radicals precipitate as sulphides (c) I group basic radicals precipitate as chlorides (d) all the above statements are correct

Step-by-Step Solution

Answer

All statements are correct (Option d).

Step 1: Understanding Precipitation of Group I Radicals

Group I basic radicals are primarily alkali metals like sodium and potassium. In qualitative analysis, Group I radicals typically form precipitates with chlorides. Therefore, statement (c) is accurate for Group I.

Step 2: Evaluating Precipitation of Group IV Radicals

Group IV basic radicals typically include lead, mercury, bismuth, and copper. These metals form precipitates as sulphides when treated with hydrogen sulfide (H₂S), making statement (b) correct for Group IV.

Step 3: Analyzing Precipitation of Group V Radicals

Group V basic radicals, like calcium, strontium, and barium, usually precipitate as carbonates. Hence, statement (a) correctly relates to the precipitation behavior of Group V radicals.

Step 4: Verifying the Correctness of All Statements

All three individual statements have been found to be correct, meaning that statement (d), 'all the above statements are correct', accurately summarizes the situation.

Key Concepts

Group I Radicals

In the world of qualitative analysis, Group I radicals are renowned for being alkali metals such as sodium and potassium. These metals share a common characteristic of forming precipitates with chlorides. When these alkali metals interact with chloride ions, they form a solid substance known as a precipitate. This means that when you add a chloride source to a solution containing Group I radicals, a visible change occurs as the solid starts to form. This is essential in helping chemists identify specific metals in a mixture. The formation of chloride precipitates is a primary feature used to identify Group I radicals in qualitative chemical analysis. Understanding this characteristic can be crucial in applications where identifying specific ions is necessary, such as in environmental monitoring and lab analysis.

Group IV Radicals

Group IV radicals consist of metals such as lead, mercury, bismuth, and copper. These metals are well known for their reaction with hydrogen sulfide (H₂S). When Group IV radicals encounter H₂S in a solution, they typically form precipitates in the form of sulfides. The resulting sulfide precipitate is usually a distinct color, which aids in the visual identification of these radicals. For instance, lead sulfide precipitates as a black solid, while bismuth sulfide appears as a brownish-black precipitate. This ability to form sulfides is a critical aspect of qualitative analysis that helps in distinguishing Group IV radicals from others. Recognizing the sulfide-precipitate characteristic of these metals is fundamental in laboratories where accurate identification of metal ions is paramount.

Group V Radicals

Group V radicals include metals such as calcium, strontium, and barium. Unlike the previous groups, these metals tend to form precipitates with carbonates. When added to a carbonate solution, these Group V metals create a solid precipitate, usually visible as a cloudiness or a fine powdery deposit. This can occur naturally in water systems, where changes in conditions lead to precipitation. The formation of carbonate precipitates is not only useful for identifying these metals in lab settings but also has practical importance in areas like water treatment and geology. By understanding how Group V radicals behave with carbonates, chemists can devise methods to isolate and identify these specific ions efficiently and accurately.