Which of the following graphs between potential energy (y-axis) vs reaction coordinate (x-axis) correctly represents the reaction profile of ? [2026]

Question

$A \to D$ is an endothermic reaction occurring in three steps (elementary).

(i) $A \to B Δ H_{i} = + ve$

(ii) $B \to C Δ H_{i i} = - ve$

(iii) $C \to D Δ H_{i i i} = - ve$

Which of the following graphs between potential energy (y-axis) vs reaction coordinate (x-axis) correctly represents the reaction profile of $A \to D$ ? [2026]

Smart Achievers · Accepted Answer

(2)

$Given:$

$A \to D; Δ_{r} H = (+) ve = E_{D} - E_{A}$ $∴ E_{D} > E_{A}$

$Mechanism$

$A \to B; Δ_{r} H = (+) ve \Rightarrow E_{B} > E_{A}$

$B \to C; Δ_{r} H = (-) ve \Rightarrow E_{C} < E_{B}$

$C \to D; Δ_{r} H = (-) ve \Rightarrow E_{D} < E_{C}$

Solution

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Ans.
(2)

$Given:$

$A \to D; Δ_{r} H = (+) ve = E_{D} - E_{A}$ $∴ E_{D} > E_{A}$

$Mechanism$

$A \to B; Δ_{r} H = (+) ve \Rightarrow E_{B} > E_{A}$

$B \to C; Δ_{r} H = (-) ve \Rightarrow E_{C} < E_{B}$

$C \to D; Δ_{r} H = (-) ve \Rightarrow E_{D} < E_{C}$

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Solution

Q. A→D is an endothermic reaction occurring in three steps (elementary). (i) A→B ΔHi=+ve (ii) B→C ΔHii=-ve (iii) C→D ΔHiii=-ve Which of the following graphs between potential energy (y-axis) vs reaction coordinate (x-axis) correctly represents the reaction profile of A→D [2026]

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4

Ans. (2) Given: A→D; ΔrH=(+)ve=ED-EA ∴ ED>EA Mechanism A→B; ΔrH=(+)ve⇒EB>EA B→C; ΔrH=(-)ve⇒EC<EB C→D; ΔrH=(-)ve⇒ED<EC

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Ans.
(2)

$Given:$

$A \to D; Δ_{r} H = (+) ve = E_{D} - E_{A}$ $∴ E_{D} > E_{A}$

$Mechanism$

$A \to B; Δ_{r} H = (+) ve \Rightarrow E_{B} > E_{A}$

$B \to C; Δ_{r} H = (-) ve \Rightarrow E_{C} < E_{B}$

$C \to D; Δ_{r} H = (-) ve \Rightarrow E_{D} < E_{C}$