1.
For a zero-order reaction, k=2×102mol L1s1k = 2 \times 10^{-2}\,\text{mol L}^{-1}\,\text{s}^{-1}. If the concentration of the reactant after 25s25\,\text{s} is 0.5M0.5\,\text{M}, the initial concentration must have been