Preparation of Dihydrogen — NEET Importance

NEET Importance Analysis

The topic 'Preparation of Dihydrogen' is of significant importance for the NEET UG examination within the Chemistry section. It frequently appears in the 'Hydrogen' chapter, which is a foundational unit in Inorganic Chemistry. Questions from this topic typically test a student's knowledge of specific reagents, reaction conditions (temperature, pressure, catalyst), and by-products for both laboratory and industrial methods.

Historically, questions have focused on distinguishing between suitable and unsuitable reagents for dihydrogen preparation (e.g., which metals react with which acids/bases, or why certain acids like nitric acid are not used). Industrial methods, particularly steam reforming of hydrocarbons and the water-gas shift reaction, are also frequently tested, often requiring knowledge of the overall process, intermediate products (like water gas), and purification steps.

Marks weightage for this specific sub-topic can range from 1 to 2 questions (4 to 8 marks) in the chemistry section, either directly or as part of a broader question on hydrogen. Common question types include direct recall of reactions, identifying the correct method for a given scale (lab vs.

industrial), explaining why certain conditions or reagents are used, and understanding the role of catalysts or purification steps. Numerical problems are rare, but stoichiometric understanding of reactions might be implicitly tested.

A strong grasp of redox principles is also beneficial, as many preparation methods involve electron transfer.

Vyyuha Exam Radar — PYQ Pattern

Analysis of NEET (and erstwhile AIPMT) Previous Year Questions (PYQs) on 'Preparation of Dihydrogen' reveals several recurring patterns and areas of emphasis. A significant number of questions revolve around identifying suitable and unsuitable reagents for laboratory preparation.

For instance, questions frequently ask why highly reactive alkali metals (Na, K) are not used with water/acids, or why oxidizing acids like nitric acid do not yield dihydrogen. This tests the understanding of reactivity series and the oxidizing nature of certain acids.

Industrial methods are another prominent area. The steam reforming of hydrocarbons, particularly methane, and the subsequent water-gas shift reaction are consistently tested. Questions often probe the specific catalysts (e.

g., Ni for steam reforming, $Fe_2O_3/Cr_2O_3$ for water-gas shift), reaction conditions (high temperature for steam reforming, moderate for water-gas shift), and the purpose of each step (e.g., converting CO to $CO_2$ and increasing $H_2$ yield).

The concept of 'water gas' and its composition is also a common point of inquiry.

Questions on electrolysis of water or brine often focus on the purity of hydrogen produced and the co-products ($O_2$, $Cl_2$, $NaOH$). The difficulty level generally ranges from easy to medium, primarily testing factual recall and conceptual understanding.

There are very few, if any, complex numerical problems directly from this sub-topic. The trend indicates a balanced focus on both laboratory and industrial methods, with a slight edge towards industrial processes due to their complexity and multi-step nature.

Students should expect direct questions on reactions, reagents, conditions, and the underlying principles.