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

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).