Question

An average reaction rate is calculated as the change in the concentration of reactants or products over a period of time in the course of the reaction. And instantaneous reaction rate is the rate at a particular moment in the reaction and is usually determined graphically. The reaction of compound A forming compound B was studied and the following data were collected:
Col1 Time 0. 200. 500. 800. 1200. 1500.
Col2 [A] (M) 0.184 0.129 0.069 0.031 0.019 0.016
What is the average reaction rate between 0. and 1500. s?rate = ??? (3 sig figs)What is the average reaction rate between 200. and 1200.s ?
rate = ??? (3 sig figs)What is the instantaneous rate of the reaction at t=800. s?rate = ?? (2 sig figs)

Answer 1

Answer:

The average reaction rate between 0 and 1500 s?rate $=1.12*10^{-4} M/s$.  The average reaction rate between 200 and 1200 s ?  rate $=1.10*10^{-4} M/s$. The instantaneous rate of the reaction at t=800 s?rate $=7.1*10^{-5} M/s$.

Explanation:

The average rate of a chemical reaction is a function of the change in the concentration of reactants  or products and the time taken for the change to happen.  The instantaneous rate is estimated by considering the average rate at the smallest possible time interval such as Δt tends to zero.

1) The average reaction rate between 0 and 1500 s?

rate = (0.184-0.016)M/(1500-0)s $=1.12*10^{-4} M/s$.

2) The average reaction rate between 200 and 1200 s ?

rate = (0.129-0.019)M/(1200-200)s $=1.10*10^{-4} M/s$.

3) The instantaneous rate of the reaction at t=800 s?

In this case, we consider the data directly before and after the given point. Such as (0.069 M, 500 s) and (0.019 M,1200 s)

instantaneous rate = (0.069 - 0.019)M/(1200-500)s $=7.1*10^{-5} M/s$.

We ignore the negative sign because we are only interested in the magnitude of the reaction rate.