00:01
For this question, you're given a graph and asked to interpret the graph to calculate average rates and some instantaneous rates.
00:11
First, you want to write for the chemical reaction an expression that describes the rate of the reaction in terms of the change in concentration of the reactant.
00:23
C4h8 with a coefficient of 1.
00:25
It's a reactant, so its concentration is decreasing, so we have a negative sign, producing 2 moles, of c2h4, so rate will be equal to 1 over the coefficient 2 multiplied by its change in concentration as a function of time.
00:42
This one will be positive because it's being created.
00:46
The graph looks something like this.
00:51
Then for part a, right, i'm sorry, part b, calculate the average rate of the reaction between 10 and 20 seconds.
00:59
So what you'll do is you will look at 10 seconds, get the concentration, look at, i said 20, 30 seconds, get the concentration, and then do a change in concentration over change in time.
01:14
That'll give us a negative slope, a negative rate of 0 .004 molar per second.
01:21
Then if we want to calculate the instantaneous rate at 20 seconds, then we need to draw a tangent right here at 20 seconds...