Chemical Kinetics - Result Question 5

5. Consider the given plot of enthalpy of the following reaction between $A$ and $B . A+B \longrightarrow C+D$

Identify the incorrect statement.

(2019 Main, 9 April II)

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(a) $D$ is kinetically stable product.

(b) Formation of $A$ and $B$ from $C$ has highest enthalpy of activation.

(c) $C$ is the thermodynamically stable product.

(d) Activation enthalpy to form $C$ is $5 $ $kJ$ $ mol^{-1}$ less than that to form $D$.

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Answer:

Correct Answer: 5. (d)

Solution:

  1. Only statement (d) is incorrect. Corrected statement is “Activation enthalpy to form $C$ is $15 $ $kg $ $mol^{-1}$ more than $5 $ $kg$ $mol^{-1}$ that is required to form $D$.” It can be easily explained by following graph.

<img src=“https://temp-public-img-folder.s3.amazonaws.com/sathee.prutor.images/sathee_image/cropped_2024_01_16_b4fdca9f34924034e8d8g-187_jpg_height_338_width_711_top_left_y_540_top_left_x_296.jpg"width="450">

Activation enthalpy (or energy) is the extra energy required by the reactant molecules that result into effective collision between them to form the products.