Question
NO_(2)(g)+NO_(3)(g)arrow N_(2)O_(5)(g) The reaction represented I above occurs in a single elementary step. The activation energy for the step is 18kJ/mol , and the overall energy change is -136kJ/mol What is the activation energy for the reverse step? Choose 1 answer: A 18kJ/mol B 118kJ/mol C 136kJ/mol D 154kJ/mol
Answer
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Ashton
Master · Tutor for 5 years
Answer
The activation energy for the reverse step is 154 kJ/mol.
Explanation
## Step 1This problem involves the concept of activation energy in relation to the rearrangement of atoms during a chemical reaction. The activation energy for the reverse reaction is the sum of the activation energy of the forward reaction and the energy change of the reaction.### **Activation Energy(reverse) = Activation Energy(forward) + Energy Change**## Step 2The given problem provides the following data: the activation energy of the forward reaction step is 18 kJ/mol, and the overall energy change of the reaction is -136 kJ/mol.## Step 3Substitute these values into the formula:### **Activation Energy(reverse) = 18 kJ/mol + (-136 kJ/mol)**## Step 4Despite the energy change being negative (as the reaction is exothermic), when calculating the activation energy for the reverse step, the endothermic energy requirement asks for the sum of the forward activation energy and the absolute magnitude of the energy change. This is due to the fact that "a negative times a negative equals a positive".## Step 5Therefore, the activation energy for the reverse step is:### **Activation Energy(reverse) = 18 kJ/mol + 136 kJ/mol**