For a zero-order reaction of the type $nA \rightarrow Products$, the integrated rate equation is given by: $$[A]_t = [A]_0 - n \cdot k \cdot t$$ Where $n$ is the stoichiometric coefficient of the reactant $A$. Here, $n=2$.
The initial concentration $[A]_0 = 2.0\ M$. The reaction is 75% complete, meaning 75% of the initial concentration has reacted. $$Amount\ reacted = 0.75 \times 2.0\ M = 1.5\ M$$ The remaining concentration $[A]_t$ is: $$[A]_t = 2.0 - 1.5 = 0.5\ M$$
Substitute the values into the rate equation: $$0.5 = 2.0 - (2 \times 1.0 \times t)$$ $$2 \times 1.0 \times t = 2.0 - 0.5$$ $$2t = 1.5$$ $$t = \frac{1.5}{2} = 0.75\ min$$
Final Answer: 0.75 min
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