**Average rate of reaction**

$\overline{){\mathbf{Rate}}{\mathbf{=}}\frac{\mathbf{\Delta}\mathbf{\left[}\mathbf{A}\mathbf{\right]}}{\mathbf{\Delta t}}}$

**a. What is the average reaction rate between 0 s and 1500 s?**

****Since A** is a reactant, the rate with respect to A is negative (–) since we’re losing reactants.*

$\frac{\mathbf{\Delta}\left[\mathbf{A}\right]}{\mathbf{\Delta t}}\mathbf{=}\mathbf{-}\frac{{\left[\mathbf{A}\right]}_{\mathbf{final}}\mathbf{-}{\left[\mathbf{A}\right]}_{\mathbf{initial}}}{{\mathbf{t}}_{\mathbf{final}}\mathbf{-}{\mathbf{t}}_{\mathbf{initial}}}$

$\frac{\mathbf{\Delta}\mathbf{\left[}\mathbf{A}\mathbf{\right]}}{\mathbf{\Delta t}}\mathbf{=}\mathbf{-}\frac{\mathbf{0}\mathbf{.}\mathbf{016}\mathbf{}\mathbf{M}\mathbf{-}\mathbf{0}\mathbf{.}\mathbf{184}\mathbf{}\mathbf{M}}{\mathbf{1500}\mathbf{-}\mathbf{0}\mathbf{}\mathbf{s}}$

$\frac{\mathbf{\Delta}\mathbf{\left[}{\mathbf{O}}_{\mathbf{2}}\mathbf{\right]}}{\mathbf{\Delta t}}$**= ****1.12****×10**^{‒4} **M/s**

**b. What is the average reaction rate between 500 s and 1200 s?**

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 s and 1500 s?

b. What is the average reaction rate between 500 s and 1200 s?

c. What is the instantaneous rate of the reaction at t = 800 s?

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