Why does a reagent have to be in large stoichiometric excess in order for the reagents term in the rate law equation to be considered pseudo-zero order?
Time (min) Absorbance
0.00 0.909
0.25 0.426
0.50 0.278
0.75 0.206
1.00 0.164
1.25 0.136
1.50 0.116
1.75 0.102
2.00 0.090
2.25 0.081
2.50 0.074
2.75 0.067
3.00 0.062
3.25 0.058
3.50 0.054
3.75 0.050
4.00 0.047
Time (min) Absorbance
0.00 0.909
0.25 0.426
0.50 0.278
0.75 0.206
1.00 0.164
1.25 0.136
1.50 0.116
1.75 0.102
2.00 0.090
2.25 0.081
2.50 0.074
2.75 0.067
3.00 0.062
3.25 0.058
3.50 0.054
3.75 0.050
4.00 0.047
1 Answer
Because then its concentration will change very little in comparison to another reagent.
By definition, that means its order is
But this requires two reagents in the reaction. Otherwise, there is no basis of comparison, and it cannot be even pseudo zero order.
If we had a pseudo first order rate law given as
#r(t) = k[A]^0[B]# ,
then if we get rid of
I don't know why you have your data there, but it's 2nd order with respect to the reagent.
#1/([A]) = kt + 1/([A]_0)# , 2nd order integrated rate law
This is the only choice of
What is the rate constant? What are its units?
