In: Chemistry
The following data were obtained for the concentration vs. time
for a certain chemical reaction. Values were measured at 1.0 s
intervals, beginning at 0.00 and ending at 20.0 s. Concentrations
in mM are:
10.00, 6.91, 4.98, 4.32, 3.55, 3.21, 2.61
2.50, 2.22, 1.91, 1.80, 1.65, 1.52, 1.36
1.42, 1.23, 1.20, 1.13, 1.09, 1.00, 0.92
a) Plot concentration, c, vs. time, t, ln
c vs. t, and 1/c vs. t.
b) Decide whether the data best fit zero-order, first-order or
second-order kinetics and calculate the rate constant (with units
(!!!)).
a)
Time | Concentration | ln C | 1/c |
0 | 10 | 2.302585 | 0.1 |
1 | 6.91 | 1.93297 | 0.144718 |
2 | 4.98 | 1.60543 | 0.200803 |
3 | 4.32 | 1.463255 | 0.231481 |
4 | 3.55 | 1.266948 | 0.28169 |
5 | 3.21 | 1.166271 | 0.311526 |
6 | 2.61 | 0.95935 | 0.383142 |
7 | 2.5 | 0.916291 | 0.4 |
8 | 2.22 | 0.797507 | 0.45045 |
9 | 1.91 | 0.647103 | 0.52356 |
10 | 1.8 | 0.587787 | 0.555556 |
11 | 1.65 | 0.500775 | 0.606061 |
12 | 1.52 | 0.41871 | 0.657895 |
13 | 1.36 | 0.307485 | 0.735294 |
14 | 1.42 | 0.350657 | 0.704225 |
15 | 1.23 | 0.207014 | 0.813008 |
16 | 1.2 | 0.182322 | 0.833333 |
17 | 1.13 | 0.122218 | 0.884956 |
18 | 1.09 | 0.086178 | 0.917431 |
19 | 1 | 0 | 1 |
20 | 0.92 | -0.08338 | 1.086957 |
b) The graph of 1/C vs Time is straight line.therefore the the given data is best fit for second order reaction
The slope of 1/C vs time graph will give us the rate constant.
Therefore slope of 1/C vs time = y/
= (0.144718- 0.1)/(1-0)
= 0.044 (mM-1 sec)
rate constant K = 0.044 sec/mM