Problem 121 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following $$ \begin{array}{ll} \hline \text { Column-I } & \text { Column-II } \\ \hline \text { (a) } \mathrm{Ce}^{4+} & \text { (p) Oxidizing agent in volu- } \\\ \text { metric analysis } \\ \text { (b) } \mathrm{Nd}^{3+} & \text { (q) Misch metal } \\ \text { (c) } \mathrm{La}^{3+} & \text { (r) Colourless salts } \\ \text { (d) } \mathrm{Pr}^{3+} & \text { (s) Coloured glases for gog- } \\ \text { gles. } \end{array} $$

Step-by-Step Solution

Answer

(a) -> (p), (b) -> (q), (c) -> (r), (d) -> (s)

Step 1: Analyze properties of Ce^{4+}

Cerium (Ce^{4+}) is known for its ability to act as a strong oxidizing agent in chemical processes. It is commonly used in volumetric analysis due to this property.

Step 2: Analyze properties of Nd^{3+}

Neodymium (Nd^{3+}) is a rare-earth metal often used in an alloy known as misch metal, which is used in making things like lighter flints.

Step 3: Analyze properties of La^{3+}

Lanthanum (La^{3+}) typically forms colorless salts. They are known for their lack of color when dissolved in solutions.

Step 4: Analyze properties of Pr^{3+}

Praseodymium (Pr^{3+}) is often used to tint glass yellow-green, which is used in making certain goggles for welding and glass-blowing.

Step 5: Match the elements to their uses

Based on the analysis: - (a) Ce^{4+} matches with (p) Oxidizing agent in volumetric analysis. - (b) Nd^{3+} matches with (q) Misch metal. - (c) La^{3+} matches with (r) Colourless salts. - (d) Pr^{3+} matches with (s) Coloured glasses for goggles.

Key Concepts

Oxidizing agent

In the realm of chemistry, an oxidizing agent plays a crucial role in facilitating reactions. An oxidizing agent is a substance that has the ability to oxidize other substances. This means it gains electrons in a chemical reaction and causes another species to lose electrons. By doing so, oxidizing agents are reduced themselves. In inorganic chemistry, oxidizing agents are fundamental in several processes. A good example is cerium, specifically the ion \( \text{Ce}^{4+} \). It is renowned for its strong oxidizing properties. This particular ion can accept electrons, making it pivotal in redox reactions where it helps in the analysis and measurements of substances. Hence, \( \text{Ce}^{4+} \) is commonly employed in volumetric analysis, which is a technique used to determine the concentration of a solution. Its efficiency in oxidizing other substances makes it indispensable for precise quantitative measurements.

Lanthanide series

The lanthanide series is a fascinating group in the periodic table, consisting of 15 elements from lanthanum (La) to lutetium (Lu). These elements are known for their similar properties, which makes them sometimes confusing to distinguish. The lanthanides are located in the f-block of the periodic table and are often collectively called rare-earth elements. What makes these elements stand out is their ability to oxidize easily and form various ions, particularly the +3 oxidation state. Lanthanum (\( \text{La} \)), neodymium (\( \text{Nd} \)), and praseodymium (\( \text{Pr} \)) are part of this series. For example, lanthanum forms colorless salts, which is a typical characteristic of some lanthanide elements when dissolved in solution. They exhibit unique properties like fluorescence and are utilized in technologies ranging from catalysts to electronics.

Rare-earth metals

Rare-earth metals, often synonymous with the lanthanide series, hold significant industrial and technological value. Despite what their name suggests, these metals are relatively abundant in the Earth's crust. However, their dispersion makes them "rare" in terms of extraction. Misch metal is an example of rare-earth utilization and consists predominantly of cerium, lanthanum, neodymium, and some other elements. Neodymium, for instance, is a component of misch metal and is integral to making strong permanent magnets and lighter flints. These metals are prized for their unique magnetic, luminescent, and catalytic properties, making them indispensable in various sectors such as electronics, renewable energy, and automotive industries.

Volumetric analysis

Volumetric analysis plays a critical role in analytical chemistry and involves measuring the volume of a solution needed to react with an analyte. This technique is essential in determining concentrations of unknown solutions accurately. This analytical method frequently utilizes oxidizing agents such as \( \text{Ce}^{4+} \) due to their reactivity and ability to facilitate precise measurements. By conducting a titration, chemists can determine how much of a solution is needed to achieve a complete reaction with a specific amount of reagent. Varied indicators can help determine the endpoint of a titration, which is when the reactants have completely reacted, and the concentration can be calculated. This precision and reliability make volumetric analysis a go-to method in laboratories for quality control and research purposes.