Example: Dehalogenation of trimethyl methyl bromide (CH3)3 CBr is given by the reaction.
The following data were obtained.
| time/h | [(CH3)3 CBr] x 10 - 2 M | Instantaneous Rate Ms-1 |
|---|---|---|
| 0 | 10.39 | |
| 3.15 | 8.96 | |
| 6.20 | 7.76 | Rate at time = 6.5 hours = 0.39 M/hr |
| 10.00 | 6.39 | |
| 18.30 | 3.53 | Rate at time = 16.2 hours = 0.23 M/hr |
| 30.80 | 2.07 |
Calculate the instantaneous rate by plotting the data as concentration versus time and taking the slope of the tangent drawn to the curve at some time t.
Suggested answer:
The plot of concentration versus time is shown in below figure. The instantaneous rates were calculated at times 6.5 hours and 16.2 hours. The rates are,
at time = 6.5 hours = 0.39 M / hrat time = 16.2 hours = 0.23 M / hr
fig 6.3
