Problem 184 - A Complete Resource Book in Chemistry for JEE Main

Question

How many of these metals are usally used as catalysts Pd, \(\mathrm{Pt}, \mathrm{Ni}, \mathrm{Na} / \mathrm{liq} \cdot \mathrm{NH}_{3}\)

Step-by-Step Solution

Answer

Three metals: Pd, Pt, and Ni are usually used as catalysts.

Step 1: Identify Metals

Look at the list of metals provided: Pd, Pt, Ni, Na. Your first task is to identify which of these are metals. All of these elements - palladium (Pd), platinum (Pt), nickel (Ni), and sodium (Na) - are metals.

Step 2: Determine Catalyst Usage

Now, determine which of these metals are usually used as catalysts. Palladium (Pd), platinum (Pt), and nickel (Ni) are commonly used as catalysts in various chemical reactions, whereas sodium (Na) is not typically used this way, especially in the presence of liquid ammonia (liq. NH₃).

Step 3: Count Usual Catalysts

Count the number of metals that are usually used as catalysts. From the determined list, Pd, Pt, and Ni are used as catalysts, giving us a count of 3.

Key Concepts

Transition Metals

Transition metals are a group of elements found in the middle of the periodic table, typically spanning from group 3 to group 12. These elements are characterized by their ability to form varied oxidation states, which makes them versatile in chemical reactions. For students seeking to understand why transition metals are important, consider the following points:

• They often have high melting and boiling points.
• These metals display a wide range of colors in solutions, due to d-d electron transitions.
• They have the ability to form complex compounds with interesting magnetic and electronic properties.

Transition metals like palladium (Pd), platinum (Pt), and nickel (Ni) are especially noted for their catalytic properties. Their electronic configurations allow them to facilitate a range of reactions, making them invaluable in industrial processes such as hydrogenation and the synthesis of various organic compounds. Their unique properties are linked to the d-orbitals that can hold electrons, allowing these metals to participate in multiple bonding states with reactants.

Catalytic Applications

Catalysts are substances that speed up chemical reactions without being consumed in the process. Transition metals are particularly effective as catalysts due to their ability to lend electrons or form temporary bonds with reactants.
The use of transition metals as catalysts has several benefits:

• They can increase reaction rates significantly, thus saving time and energy.
• These metals can provide an alternative pathway with a lower activation energy.
• They can be easily recovered and reused after the reaction.

Palladium (Pd) and platinum (Pt), for example, are widely used in the automotive industry for catalytic converters, transforming toxic fumes into less harmful substances. Moreover, nickel (Ni) is often utilized in hydrogenation reactions, where it aids in the addition of hydrogen to unsaturated organic compounds. The role of these metals is crucial in improving efficiency and sustainability in chemical manufacturing.

Chemical Reactions

Chemical reactions are the processes by which substances interact to form new products. Understanding how reactions occur can help in grasping the role of catalysts.
In a typical chemical reaction, reactants undergo transformation into products through the breaking and forming of chemical bonds. A catalyst, such as a transition metal, participates in the reaction process by lowering the activation energy needed to initiate it. This means reactions can occur more quickly or at lower temperatures.

• Catalysts provide an alternative pathway for the reaction, leading to faster completion.
• They do not alter the initial or final energy states of the reactants/products but make the reaction more efficient.
• In heterogeneous catalysis, the catalyst is in a different phase than the reactants, like solid catalysts for gaseous reactants.

It's essential to note that while catalysts speed up reactions, they are not consumed, meaning they can act repeatedly. This can make industrial processes more cost-effective and environmentally friendly. Understanding these principles helps students appreciate the significance of transition metals in catalysis beyond just memorizing their functions.