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. An 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:

Time (s) [A](M)
0. 0.184
200. 0.129
500. 0.069
800. 0.031
1200. 0.019
1500. 0.016

a.) What is the average reaction rate between 0. and 1500. s?
b.) What is the average reaction rate between 200. s and 1200. s?
c.) What is the instantaneous rate of the reaction at t=800 s?

Answer 1

Answer:

a) 0.000112 M/s is the average reaction rate between 0.0 seconds and 1500.0 seconds.

b) 0.00011 M/s is the average reaction rate between 200.0 seconds and 1200.0 seconds.

c) Instantaneous rate of the reaction at t=800 s :

Instantaneous rate  : $\frac{0.031 M}{800.0 s}=3.875\times 10^{-5} M/s$

Explanation:

Average rate of the reaction is given as;

$R_{avg}=-\frac{\Delta A}{\Delta t}=\frac{A_2-A_1}{t_2-t_1}$

a.) The average reaction rate between 0.0 s and 1500.0 s:

At 0.0 seconds the concentration was  = $A_1=0.184 M$

$t_1=0.0s$

At 1500.0 seconds the concentration was  = $A_2=0.016 M$

$t_2=1500 s$

$R_{avg]=-\frac{0.016 M-0.184 M}{1500.0 s-0.0 s}=0.000112 M/s$

0.000112 M/s is the average reaction rate between 0.0 seconds and 1500.0 seconds.

b.) The average reaction rate between 200.0 s and 1200.0 s:

At 0.0 seconds the concentration was  = $A_1=0.129 M$

$t_1 =200.0 s$

At 1500.0 seconds the concentration was  = $A_2=0.019M$

$t_2=1200 s$

$R_{avg]=-\frac{0.019 M-0.129M}{1200.0s-200.0s}=0.00011 M/s$

0.00011 M/s is the average reaction rate between 200.0 seconds and 1200.0 seconds.

c.) Instantaneous rate of the reaction at t=800 s :

At 800 seconds the concentration was  = $A=0.031 M$

$t =800.0 s$

Instantaneous rate  : $\frac{0.031 M}{800.0 s}=3.875\times 10^{-5} M/s$