2. Calculate the rate constant, k, using the slope of the linear regression line

Question

2. Calculate the rate constant, k, using the slope of the linear regression line for your linear curve (k=1 slope for zero and first order and k=slope for the second order). Be sure to include correct units for the rate constant. Note: This constant is sometimes referred to as the pseudo constant, because it does not take into account the effect of the other reactant, OH-

3. Write the correct rate law expression for the reaction, in terms of crystal violet (omit OH-)

Linear fit for Ln(Absorbance)

Ln(A)=mt+b

m(slope) -0.001859

b(Y-intercept) -1.046

Correlatio -0.9998

RMSE 0.007510

Explanation / Answer

2. The reaction is pseudo first order (since [OH-] remains constant) and we have

ln[A] = mt + b where m = -0.001859 is the slope of the plot and b = -1.046 is the y-intercept; t is the time.

Since the left hand side involves a logarithmic term, the left hand side is dimensionless; therefore, the right hand side must be dimensionless as well. Again, we have ln[X] = kt + c where k = rate constant and [X] is the concentration of the reactant; c is the intercept.

Since t has unit sec and the right side is dimensionless, the unit for k must be sec-1. Also, from the linear regression plot, we know

k = -slope = -(-0.001859) sec-1 = 0.001859 sec-1 = 1.859*10-3 sec-1 (ans).

3. I need to see the experiment to write out the correct rate law; kindly upload the experiment.

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