Problem 40 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the properties of interstitial hydrides is correct? (a) They give rise to metals fit for fabrication (b) They generally form non-stoichiometric species (c) They can be used as hydrogenation catalysts (d) The hydrogen dissolved in titanium improves its mechanical properties

Step-by-Step Solution

Answer

(b) They generally form non-stoichiometric species.

Step 1: Understanding Interstitial Hydrides

Interstitial hydrides are compounds formed when hydrogen atoms occupy the interstitial spaces in a metal lattice without causing significant distortion. These types of hydrides are typically formed by transition metals.

Step 2: Exploring Non-Stoichiometry

Interstitial hydrides often form non-stoichiometric compounds. This means their hydrogen-to-metal ratio can vary instead of being fixed, leading to compositions like TiH_x, where the value of x can vary depending on conditions.

Step 3: Evaluating Stoichiometry in Hydrides

Non-stoichiometric nature is a characteristic of interstitial hydrides because the precise number of hydrogen atoms in the lattice can change based on external conditions such as temperature and pressure.

Key Concepts

Non-Stoichiometry

Non-stoichiometry is a term that might sound complicated, but it's simply about variations in component ratios within a compound. When we're discussing interstitial hydrides, non-stoichiometry becomes a noteworthy concept. These hydrides often don't have a fixed formula like many other chemical compounds.
Instead, they have a ratio of hydrogen to metal that can change. This is especially true for transition metals when they form hydrides. Imagine it as having a recipe where the amount of one ingredient doesn't have to be precise to still get a delicious result.

• This varying ratio can result due to factors such as changing temperature or pressure.
• For instance, in titanium hydrides, the formula may look like TiH_x, where x can change based on conditions.

Non-stoichiometry allows these hydrides to have unique properties, such as adjusting hydrogen content without altering the general structure much. This occurrence is quite useful, especially in fields like material science and chemistry.

Transition Metals

Transition metals are a fascinating group of elements found in the central part of the periodic table. These metals are known for their ability to form various compounds, including interstitial hydrides.
One special property of transition metals is their lattice structure, which can safely accommodate small atoms like hydrogen in the interstices without much distortion.
When transition metals form interstitial hydrides, the hydrogen atoms slip into these empty spaces within the metal lattice. This characteristic makes them quite different from typical ionic or covalent compounds.

• This capacity to absorb hydrogen is why many transition metals are used in creating non-stoichiometric hydrides.
• Examples of such metals include titanium, palladium, and zirconium, among others.

These metals are extremely versatile in chemical reactions and are crucial in industries where hydrogen storage and utilization are important.

Hydrogenation Catalysts

When we talk about hydrogenation catalysts, we're essentially referring to substances that speed up chemical reactions involving hydrogen. Interstitial hydrides, involving transition metals, can serve as effective catalysts in such hydrogenation processes.
Transition metals like nickel and palladium are often used in these reactions. Why? Because they can absorb hydrogen and then release it to react with other substances, thus facilitating the hydrogenation process.
Here's how it works:

• Hydrogen atoms are first absorbed by the metal lattice.
• They are then made available to react with target molecules, often unsaturated organic compounds, to form saturated compounds.

This property is invaluable in numerous industrial applications, such as food processing and petrochemical industries, where hydrogenation is a key process. The ability of these catalysts to perform efficiently is vital for producing various goods and substances.