The first-order decomposition of a colored chemical species, X, into colorless products is monitored with a spectrophotometer by measuring changes in absorbance over time. Species X has a molar absorptivity constant of 5.00 x 10^3 cm^ -1 M^ -1 and the path length of the cuvette containing the reaction micture is 1.00 cm. The data from the experiment are given in the table below.

[X] Absorbance Time(min)

(M)

? 0.600 0.0

4.00 x 10^ -5 0.200 35.0

3.00 x 10^ -5 0.150 44.2

1.5 x 10^ -5 0.075 ?

a) calculate the initial concentration of the colored species.

- I got 1.2 * 10 ^ -4 is that right?

b) calculate the rate constant for the first-order reaction using the values given for concentration and time. Include unites with your answer.

- I got 0.0314, however I do not know if this is correct and will the units be cm ^ -1 M ^ -1

c) calulate the number of minutes it takes for the absorbace to drop from 0.600 to 0.075

how do you do this?

d) calculate half-life of the reation. Include units with your answer.

e)

http://www.collegeboard.com/prod_dow...-chem-0607.pdf
question # 3

I WOULD REALLY APPRECIATE if you help me out, it is really confusing!

THANKS!