The concentration of A is 0.2 mol/L.
Explanation:
The chemical equation for your reaction is
2A → A 2
The integrated rate law for a second-order reaction is
1 [ A ] t = 1 [ A ] 0 + k t
where
1 [ A ] t = the concentration of A at time t
1 [ A ] 0 = the concentration of A at time t = 0
(i.e., at the beginning of the reaction)
k m l l = the rate constant for the reaction
In this problem,
[ A ] 0 = 4.50 mol/L
k m l = 0.0265 L⋅mol -1 min - 1
t m l l = 180.0 min
∴ 1 [ A ] t = (1 / 4.50 mol/L ) + 0.0265 L⋅mol -1 min - 1 × 180.0 min
= 0.2222 L⋅mol -1 + 4.770 L⋅mol -1
= 4.992 L⋅mol -1
[ A ] t = 1 / 4.992 L⋅mol -1
= 0.2 mol/L
The concentration of A is 0.2 mol/L.
