Calculating rate of reaction
Average rate of reaction
The rate of reaction can change during the course of a reaction. The average rate of reaction can be calculated using:
- data from a table of results, or
- values from a graph
To find out the average rate of reaction at 20 seconds:
\(\frac{volume~of~product}{time} = \frac{40}{20}\)
= 2 cm3/s
Question
During a reaction between hydrochloric acid and calcium carbonate, it takes 20 seconds to collect 80 cm3 of carbon dioxide.
What is the average rate of reaction over this time?
The average rate of reaction
\(\frac{volume~of~product}{time}\)
\(\frac{80}{20}\)
= 4 cm3/s
Rate of reaction at a specific time
The rate of reaction at a specific time is equal to the gradient of the graph at that time - it is equal to the gradient of the A straight line that just touches a point on a curve. A tangent to a circle is perpendicular to the radius which meets the tangent..
Rate of reaction at 20 seconds
= gradient of tangent
= \(\frac{60}{20}\)
= 3 cm3/s