The ionization constant of NH4+ in water is 5.6 × 10^-10 mol L^-1 at 25°C. The rate constant for the reaction of NH4+ and OH- to form and at 25°C is 3.4 × 10^10 L mol^-1 s^-1. The rate constant for pr

Question

The ionization constant of NH4+ in water is 5.6 × 10^-10 mol L^-1 at 25°C. The rate constant for the reaction of NH4+ and OH- to form $NH_3$ and $H_2O$ at 25°C is 3.4 × 10^10 L mol^-1 s^-1. The rate constant for proton transfer from water to $NH_3$ at 25°C is

Prashant Kotian · Accepted Answer

Correct answer: A. The reaction is: NH4+ + OH- ⇌ + with forward rate constant kf = 3.4 × 10^10 L mol^-1 s^-1 and reverse rate constant kb. The equilibrium constant for this reaction is K = kf / kb. Also, this reaction is the reverse of the basic dissociation of : + ⇌ NH4+ + OH- (Kb). Thus, K = 1 / Kb = Ka / Kw = 5.6 × 10^-10 / 10^-14 = 5.6 × 10^4. Therefore, kf / kb = 5.6 × 10^4 => kb = kf / (5.6 × 10^4) = 3.4 × 10^10 / (5.6 × 10^4) = 6.07 × 10^5 s^-1.

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