Hydrogen: Chemical Properties - NEET Notes, Formula & Common Mistakes
HydrogenChemical PropertiesNEET ChemistryNEET 2025Reactions with MetalsNonmetalsOxides
Hydrogen: Chemical Properties - NEET Notes, Formula & Common Mistakes
Hydrogen·2 min read·NEET 2026
What NEET Asks
Conceptual questions on types of hydrides formed with different elements.
Reaction identification and balancing, especially involving hydrogen as a reducing agent.
Conditions required for specific reactions (temperature, pressure, catalyst).
Key Points
Hydrogen reacts with highly electropositive metals (Group 1 & 2) to form ionic/saline hydrides (e.g., NaH, CaH₂).
It reacts with non-metals to form covalent hydrides (e.g., H₂O, NH₃, HX).
With oxygen, H₂ burns to form water: (highly exothermic).
2H₂(g) + O₂(g) → 2H₂O(l)
With halogens (X₂), it forms hydrogen halides (HX), with reactivity decreasing from F₂ to I₂.
Hydrogen acts as a reducing agent, reducing oxides of less active metals (e.g., CuO, Fe₂O₃) to their respective metals.
Conditions are crucial: high temperature often required, catalysts for specific reactions (e.g., Haber's process for NH₃).
Must-Know Formula / Reaction
Reduction of metal oxides:MO(s) + H₂(g) → M(s) + H₂O(l/g)
MO: Oxide of a less active metal (e.g., CuO, Fe₂O₃)
H₂: Hydrogen gas, acts as a reducing agent
M: Pure metal
H₂O: Water
Common Mistakes
Students often confuse ionic and covalent hydrides; remember ionic hydrides are formed with highly electropositive metals.
Don't forget reaction conditions; for instance, the reaction with nitrogen (Haber's process) requires specific temperature, pressure, and catalyst.
Misinterpreting hydrogen's role: it's primarily a reducing agent in reactions with metal oxides, not an oxidizing one.
Rapid Revision
Hydrogen forms ionic hydrides with active metals and covalent hydrides with non-metals. It reduces metal oxides to metals and forms water with oxygen. Reactivity with halogens decreases down the group. Always check specific reaction conditions.
Frequently Asked Questions
What kind of hydrides does hydrogen form?▾
Hydrogen forms ionic (saline) hydrides with highly electropositive Group 1 and Group 2 metals. With non-metals, it forms covalent (molecular) hydrides like H₂O, NH₃, and HX.
Is hydrogen a reducing or oxidizing agent?▾
Hydrogen primarily acts as a reducing agent, especially at elevated temperatures. It can reduce oxides of less active metals (like copper, iron) to their metallic forms by removing oxygen, forming water.
What are the key conditions for hydrogen's reactions?▾
Reaction conditions for hydrogen are crucial and vary widely. For example, its reaction with nitrogen to form ammonia (Haber's process) requires high temperature, high pressure, and a catalyst. With halogens, reactivity and conditions differ significantly, from explosive with fluorine to slow and reversible with iodine.
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