According to the second order formula: 1/[At] = K t + 1/[Ao] and when we have the K constant =0.0265 & we have t = 180 min & we have the initial concentration of A = 4.25 so by substitution:
1/[At] = 0.0265 X 180min + 1/4.25 1/[At] = 5 ∴[At] = 1/5 = 0.2 m
