JEE Main 2026 Apr 5 Shift 2, Chemistry Q25: Reactions of Various Orders

JEE Main2026Apr 5, Shift 2Chemistry

For a reaction $A \to P$ at $T$ K, the half life ( $t_{1/2}$ ) is plotted as a function of initial concentration $[A]_{0}$ of A as given below. The value of $x$ in the given figure is _____ s. (Nearest integer)

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Solution

For a reaction of order $n$ , $t_{1/2} \propto [A]_{0}^{1 - n}$ . The plot of $t_{1/2}$ vs $[A]_{0}$ is a straight line through the origin, so $t_{1/2} \propto [A]_{0}^{1}$ , giving $1 - n = 1$ , hence $n = 0$ (zero-order).

For zero order: $t_{1/2} = \frac{[ A ] _{0}}{2 k}$ , i.e. ratio is preserved:

$\frac{x}{240} = \frac{1.5 \times 1 0 ^{- 3}}{4 \times 1 0 ^{- 3}} = \frac{1.5}{4}$ .

$x = 240 \times \frac{1.5}{4} = 90$ s.

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JEE Main 2026 Apr 5 Shift 2, Chemistry Q25: Reactions of Various Orders

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