An exothermic reaction A → B has an activation energy of 17 kJ per mo...
Exothermic reaction
According to graph,
Ea(b) = Ea(f) + DH
= 17 + 40
= 57 kJ mol–1
An exothermic reaction A → B has an activation energy of 17 kJ per mo...
Calculation of Activation Energy for Reverse Reaction
Given: Activation energy (Ea) for forward reaction A → B is 17 kJ/mol of A
Heat of the reaction (ΔH) is 40 kJ
Step 1: Write the Balanced Equations for Both Reactions
Forward reaction: A → B
Reverse reaction: B → A
Step 2: Apply the Relationship Between Activation Energy and Heat of Reaction
The activation energy for the reverse reaction (Ea,rev) can be calculated using the following relationship:
ΔHrev = ΔHfor - Ea,for + Ea,rev
where,
ΔHrev is the heat of the reverse reaction
ΔHfor is the heat of the forward reaction
Ea,for is the activation energy of the forward reaction
Ea,rev is the activation energy of the reverse reaction
Step 3: Substitute the Given Values in the Equation
ΔHrev = ΔHfor - Ea,for + Ea,rev
ΔHrev = -40 kJ/mol - 17 kJ/mol + Ea,rev
ΔHrev = -57 kJ/mol + Ea,rev
Ea,rev = ΔHrev + 57 kJ/mol
Step 4: Calculate the Activation Energy for the Reverse Reaction
Ea,rev = ΔHrev + 57 kJ/mol
We know that the reverse reaction is the opposite of the forward reaction, so its heat of reaction is the negative of the forward reaction:
ΔHrev = -ΔHfor = -40 kJ/mol
Ea,rev = -40 kJ/mol + 57 kJ/mol
Ea,rev = 17 kJ/mol
Therefore, the activation energy for the reverse reaction B → A is 17 kJ/mol. The correct option is (B).
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