Govt Exams
This is an exothermic reaction (ΔH negative). By Le Chatelier's principle, decreasing temperature shifts equilibrium towards the products (right), favoring the exothermic forward reaction.
At equilibrium, Kc = kf/kr. Given Kc = 4, this means kf = 4kr, indicating the forward reaction is faster than the reverse reaction.
pH = pKa + log([A⁻]/[HA]). pKa = -log(1.8 × 10⁻⁵) ≈ 4.74. Since [A⁻] = [HA] (equal concentrations), log(1) = 0. Therefore, pH = 4.74.
The Gibbs free energy equation is ΔG = ΔH - TΔS, where T is temperature in Kelvin. This is fundamental to predicting spontaneity.
The overall order of a reaction is the sum of all exponents in the rate law. Here, order = 2 + 1 = 3.
For a first-order reaction, t₁/₂ = 0.693/k = 0.693/0.693 = 1 s. This uses the relationship ln(2) ≈ 0.693.
HCl is a strong acid and completely dissociates. [H⁺] = 0.01 M = 10⁻² M. Therefore, pH = -log[H⁺] = -log(10⁻²) = 2.
The equilibrium constant expression follows the law of mass action where Kc = [products]^coefficients/[reactants]^coefficients. For this reaction, Kc = [NH₃]²/([N₂][H₂]³).