Consider the given plot of enthalpy of the following reaction between A and B: {A + B C + D} Identify the incorrect…
Chemical Kinetics · Class 12 · JEE Main Previous Year Question
Consider the given plot of enthalpy of the following reaction between A and B:
Identify the incorrect statement.
- a
Formation of A and B from C has highest enthalpy of activation.
- b
D is kinetically stable product.
- c
C is the thermodynamically stable product.
- d✓
Activation enthalpy to form C is less than that to form D.
Activation enthalpy to form C is less than that to form D.
From the enthalpy profile for (two competing pathways):
- C is the thermodynamically stable product (lower energy/enthalpy).
- D is the kinetically stable product (lower activation energy to form D, so it forms faster).
- The reverse reaction (C or D → A + B) has the highest activation energy for the C pathway.
Evaluating statements:
(1) TRUE — Formation of A and B from C requires overcoming the highest energy barrier (reverse of the C pathway). ✓
(2) TRUE — D is kinetically stable (formed faster due to lower ). ✓
(3) TRUE — C is thermodynamically stable (lower energy product). ✓
(4) FALSE — From the graph, the activation enthalpy to form C is higher than to form D (D is kinetically favoured). The statement says C's is 5 kJ/mol less than D's, which contradicts the graph. ✗
Answer: Option (4)
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