The table shows the concentration of a reactant in the reaction mixture over a period of time.

\begin{tabular}{|l|l|}
\hline
Time (s) & Concentration (M) \\
\hline
0 & 1.8 \\
\hline
210 & 1.2 \\
\hline
450 & 0.8 \\
\hline
580 & 0.6 \\
\hline
720 & 0.4 \\
\hline
\end{tabular}

What is the average rate of the reaction over the first 580 seconds?

A. [tex]$1.6 \times 10^{-3}$[/tex] M/s
B. [tex]$1.9 \times 10^{-3}$[/tex] M/s
C. [tex]$2.0 \times 10^{-3}$[/tex] M/s
D. [tex]$2.2 \times 10^{-3}$[/tex] M/s



Answer :

To determine the average rate of the reaction over the first 580 seconds, we need to follow these steps:

1. Identify the initial concentration and the concentration at 580 seconds from the table.
- At time [tex]\( t = 0 \)[/tex] seconds, the concentration is [tex]\( 1.8 \)[/tex] M.
- At time [tex]\( t = 580 \)[/tex] seconds, the concentration is [tex]\( 0.6 \)[/tex] M.

2. Calculate the change in concentration ([tex]\( \Delta [A] \)[/tex]):
[tex]\[ \Delta [A] = \text{Initial concentration} - \text{Concentration at 580 s} = 1.8 \, \text{M} - 0.6 \, \text{M} = 1.2 \, \text{M} \][/tex]

3. Determine the time interval ([tex]\( \Delta t \)[/tex]):
[tex]\[ \Delta t = 580 \, \text{seconds} - 0 \, \text{seconds} = 580 \, \text{seconds} \][/tex]

4. Calculate the average rate of the reaction using the formula for the rate of reaction:
[tex]\[ \text{Average rate} = \frac{\Delta [A]}{\Delta t} \][/tex]
Substituting the values we have:
[tex]\[ \text{Average rate} = \frac{1.2 \, \text{M}}{580 \, \text{seconds}} = 0.00206896551724138 \, \text{M/s} \][/tex]

5. Convert this value into scientific notation to match the given options:
[tex]\[ 0.00206896551724138 \, \text{M/s} \approx 2.069 \times 10^{-3} \, \text{M/s} \][/tex]

From the provided answer choices:
- [tex]\( 1.6 \times 10^{-3} \)[/tex]
- [tex]\( 1.9 \times 10^{-3} \)[/tex]
- [tex]\( 2.0 \times 10^{-3} \)[/tex]
- [tex]\( 2.2 \times 10^{-3} \)[/tex]

The closest value to [tex]\( 2.069 \times 10^{-3} \)[/tex] M/s is [tex]\( 2.0 \times 10^{-3} \)[/tex] M/s. Therefore, the average rate of the reaction over the first 580 seconds is:

[tex]\[ \boxed{2.0 \times 10^{-3}} \][/tex]