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

Reactant Concentration

Time Concentration

0 s 1.8 M

210 s 1.2 M

450 s 0.8 M

580 s 0.6 M

720 s 0.4 M

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

A. 1.6 * 10-3

B. 1.9 * 10-3

C. 2.0 * 10-3

D. 2.2 * 10-3

C. 2.0 x 10⁻³

Explanation:

The average rate of a reaction is the rate of change of the concentration of the reactants (or products) with time.

The average rate of the reaction = - (ΔC) / (Δt).

∵ The concentration of the reactants changes from 1.8 M to 0.6M for 580 s.

∴ The average rate of the reaction over the first 580 seconds

= - (ΔC) / (Δt) = - [ (0.6M) - (1.8 M) ]/[ (580.0 s) - (0.0 s) ] = 2.0 x 10⁻³ M. s⁻¹.

So C. 2.0 x 10⁻³ is the right answer