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🧪 Chemistry  ·  Some Basic Concepts of Chemistry  ·  NEET & JEE

For the reaction N2 + 3H2 -> 2NH3, if 1 mole of N2 is mixed with 2 moles of H2, the limiting reagent is:

Answer: H2.

  • A N2
  • B H2
  • C NH3
  • D neither reagent

Correct answer: B. H2

Explanation: 1 mole N2 requires 3 moles H2, but only 2 moles are available, so H2 runs out first and is the limiting reagent.

Mass (g)given substanceMoles (n)amount of substanceParticlesatoms / moleculesGas Volumeat STP (litres)divide byMolar Massmultiply by6.022 x 10^23multiply by22.4 L/mol

Mass connects to moles via molar mass, and moles connect to particle count via Avogadro's number or to gas volume via the 22.4 L/mol rule at STP.

Concept context

The mole is chemistry's counting unit. Learn to relate mass, volume, and number of particles using Avogadro's number and molar mass, the foundation of all stoichiometry and reaction calculations.

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