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

Question

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

Step-by-Step Solution

Answer

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

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

Ce^{4+} is known for its ability to act as a strong oxidizing agent. It is commonly used in volumetric analysis to titrate solutions due to this oxidizing property. Thus, Ce^{4+} matches with (p) Oxidizing agent in volumetric analysis.

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

Nd^{3+} is part of "misch metal" which is an alloy commonly used in making lighter flints. It is not particularly known for being colorless. Thus, Nd^{3+} matches with (q) Misch metal.

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

La^{3+} compounds are typically colorless due to their lack of unpaired electrons, resulting in no absorption in the visible region of the electromagnetic spectrum. Therefore, La^{3+} matches with (r) Colourless salts.

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

Praseodymium ions such as Pr^{3+} are used in making colored glasses and goggles for their ability to absorb certain wavelengths of light, lending a green or yellow hue. Thus, Pr^{3+} matches with (s) Coloured glasses for goggles.

Key Concepts

Oxidizing Agents

Oxidizing agents are substances that have the ability to accept electrons during a chemical reaction. This process is known as oxidation. One well-known member of the lanthanide series, cerium, especially in the form of Ce^{4+}, is a potent oxidizing agent. It is commonly employed in volumetric analysis. This type of analysis generally entails titrating solutions to determine their concentrations.
This is because Ce^{4+} can efficiently exchange electrons, helping to pinpoint the endpoint of these titration processes.
Thus, Ce^{4+} is often a go-to choice in laboratories that involve precision chemical analysis.

Misch Metal

Misch metal is an alloy composed of rare earth elements, predominantly lanthanides. It usually contains lanthanum, cerium, neodymium, and praseodymium, among others. Among these, neodymium ( Nd^{3+}) stands out for its notable role within the alloy.
This particular alloy is widely used in applications that require the production of sparks. A typical example includes lighter flints, where the friction against a rough surface results in the production of sparks.
Such applications capitalize on misch metal's ability to easily ignite sparks due to its specific elemental composition.

Colorless Compounds

Certain lanthanide compounds, such as those formed with lanthanum ( La^{3+}), are typically colorless. This characteristic is attributed to their electronic structure. Specifically, The absence of unpaired electrons results in no absorption within the visible spectrum of light.
This means they do not exhibit color, and appear transparent or colorless to the human eye.
Such compounds are often utilized where a clear, unobstructed appearance is required, such as optical lenses and certain chemical applications that demand transparency.

Colored Glasses

Lanthanide elements have the unique ability to alter the color properties of materials due to their specific electronic configurations. Praseodymium ( Pr^{3+}) is one such element that plays a vital role in producing colored glasses. These ions absorb specific wavelengths of light, giving rise to vibrant hues.
As a result, they are often incorporated into the production of glass for goggles and other optical uses. These glasses can appear yellow or green, providing not only aesthetic qualities but practical benefits, such as reducing glare or filtering certain types of light.
Hence, colored glasses enhanced with Pr^{3+} ions find utility in both fashion and functionality across various industries.