Time Interval for measuring Rate of Reaction

[rpullo]

So we did a dry lab in class, and we were determining sources of error for a particular lab dealing with the measurement of rate of reaction. My teacher said that the time intervals of the recorded concentration was too far apart (1 minute intervals).
I was wondering if anyone would explain why this is a source of error? My teacher never said anything about it.
Thanks

 

[PhaseShifter]

Concentrations will not vary in a linear manner over time. Reactions will slow down as they approach completion (or equilibrium). Eventually the error in your concentration measurements will be greater than the difference between successive measurements.

The more time you wait between measurements, the fewer measurements you can make before this happens.

 

[Borek]

To reword PhaseShifter comment - if the reaction is too fast, you don't have enough data points. In the border case if the reaction is fast enough, it ends before your first measurement.

--