: 200
Systematic approach for JEE stoichiometry: (1) Read carefully — identify given and required quantities. (2) Write balanced equation. (3) Convert everything to moles first. (4) Identify limiting reagent if two reactants given. (5) Use mole ratio. (6) Convert to required units. Common shortcuts: for gas at STP, use 22.4 L/mol directly. For solutions: moles = M x V(L). For equivalence: meq = meq avoids balancing the full equation. Quick checks: mass should be conserved. Moles of product cannot exceed moles allowed by limiting reagent. Gas volumes at same T,P are proportional to moles. Frequent errors: (a) Not balancing the equation before using coefficients. (b) Using mass ratios instead of mole ratios. (c) Forgetting to identify limiting reagent. (d) Confusing STP values (22.4 L vs 24.5 L). (e) Using wrong n-factor. (f) Not converting mL to L when using molarity. Units analysis: always check that units cancel correctly.