[ABD]

Some reactions are so rapid that they are "diffusion controlled"; that is, the reactants react as quickly as they can collide. An example is the neutralization of H3O+ with an equal concentration of OH- which has the rate law: rate= k[H3O+]². The rate constant has a value of 1.3 x 10^11 M^-1
s^-1 at 25⁰C.

(a) If exactly equal volumes of 2.0M HCl and 2.0M NaOH are mixed instantaneously, how much time is required for 99.999% of the acid to be neutralized? What is the solution pH at this point in time?

(b) If exactly equal volumes of 2.0M HCl and 2.0M NaOH are mixed instantaneously, what is the pH of the solution after neutralization is complete? How much time is required for the solution to reach this pH?

(c) How many times larger is the time required to reach equilibrium than the time to neutralize 99.999% of the acid? In molecular terms, explain why it takes so long to go from 99.999% neutralization to complete neutralization.

[Borek]

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[ABD]

a) If 99.999% acid is neutralized, 0.001% is left. 0.001% of 2.0 M= 2 x 10^-5 M-------[H3O+]t
pH= - log (2 x 10^-5 M)
Use rate law: 1/[H3O+]t - 1/[H3O+] = kt ⇒ 1/( 2 x 10^-5) - 1/2 = 1.3 x 10^11 x t. cross multiply to find t.

b)HCl and NaOH are strong acid and base, respectively. So, pH is 7. [H+]= 10^-pH= 10^-7.
Use rate law: 1/(10^-7) - 1/2= 1.3 x 10^11 x t. cross multiply to find t.

c) time in b/ time in a. I think it takes longer to completely neutralize because there is a hydrogen ion conc. initially that has to be fully neutralized.

This is what I came up with!