Govt Exams
For a first-order reaction, ln[A] = ln[A]₀ - kt, so a plot of ln[A] vs t gives a straight line with slope -k.
The overall reaction is obtained by adding all steps and canceling intermediates: A + B + D → E + F. Rate law is determined by the slow step: rate = k[A][B]
Using ln([A]₀/[A]ₜ) = kt, ln(0.5/0.25) = k × 30, ln(2) = k × 30, k = 0.693/30 = 0.0231 s⁻¹
Activation energy is the minimum energy required for reactants to overcome the energy barrier and form products. It is always positive and independent of temperature.
The units s⁻¹ or time⁻¹ indicate a first-order reaction. For first-order reactions, the rate constant has units of time⁻¹.
For a zero-order reaction, t₁/₂ = [A]₀/(2k), which is directly proportional to initial concentration.
The color of the reaction vessel does not affect the reaction rate. Temperature, nature of reactants, concentration, pressure, and catalyst are actual factors affecting reaction rate.
Using Nernst equation: Ecell = E°cell - (0.059/n)log(Q). Increasing [Zn²⁺] increases Q, making the log term positive, which decreases Ecell. ΔE = -(0.059/2)log(10) = -0.0295 ≈ -0.0296 V.
At cathode: Na⁺ + e⁻ → Na; moles of Na = 2.3/23 = 0.1 mol. At anode: 2Cl⁻ → Cl₂ + 2e⁻; for 0.1 mol Na, electrons = 0.1 mol, so Cl₂ moles = 0.1/2 = 0.05 mol. Volume at STP = 0.05 × 22.4 = 1.12 L.
Kohlrausch's law: Λ°m(NaCl) = Λ°m(HCl) + Λ°m(KCl) - Λ°m(KOH) = 426 + 150 - 248 = 328 S·cm²/mol.