4 What is the concentration of crystal violet immediately af

4. What is the concentration of crystal violet immediately after mixing with NaOH, before any reaction takes place, in Step 6A? a. b. How long wil i take for the concentration of Crystal Violet to decrease to 2.0x10 M?

Solution

Analysing the graphs using RMSE value (an absolute measure of bet fitted curve)

Lowest RMSE of ln Abs Vs time graph shows that it is the best fit linear graph.So, the reaction order must be first order.

rate=k[CV+]

integrated rate law,

ln{[CV+]t/[CV]o}=-kt

[CV]o=initial concentration just after mixing NaOH

[CV+]t=concentration at time t

k=rate constant

a) 10ml of CV+ of 2.0*10^-5 M +10ml of 0.02M

[CV]o=2.0*10^-5 M*(10ml/20ml)=1.0*10^-5M

b)[CV+]t=2.0*10^-6

using first order integrated rate equation,ln{[CV+]t/[CV]o}=-kt

ln[CV+]t -ln[CV]o =-kt where slope =-k (for linear graph)

from the first order graph, between ln Abs Vs t of the form y=mx+c with slope=m=-0.0034342

So k=0.0034342 s^-1

putting thevalue of k,[CV]o,[CV]t in the above eqn time can be calculated out:

ln(2.0*10^-6/1.0*10^-5)=-(0.0034342 s^-1)t

or,t=468.65 s=468.65s*(1min/60s)=7.8 min