The data below is for the reaction sequence A ⟶ B ⟶ C ⟶ D.
Elementary step ΔrH/kJ mol−1 Ea/kJ mol−1
A ⟶ B 24 48
B ⟶ C -12 36
C ⟶ D -48 24
how can i solve Ea forward, reverse, and rH given the above info?
sorry that doesnt look clear. the 24, -12, and -48 are the ΔrH/kJ mol−1, and the 48, 36, 24 are for Ea/kJ mol−1
I'm sorry Kevin but I don't understand.
I can't tell what is forward and what is reverse.
By the way, if you have a problem lining up colums, I do this. It isn't perfect but at least it's an improvement.
....................A................B................C
I...................35...............0..................10
add.................................10..........................
C.................-10..............10.................10
E...................25...............10................10
The dots help space the html which is the code on the page.
i see, thanks! tha'ts the thing - the question is asking to calculate Ea forward, Ea reverse, and rH. i got rH because i just added all of the ΔrH/kJ mol−1 and got the ans as -36. but am unsure how to find Ea forward and reverse. i think we have to draw a graph accurately to determine that, but im still not getting it
Well, solving for activation energies and reaction enthalpies can be quite tricky, but fear not, I am here to help you through it, even if it means clowning around a bit!
To begin, let's first define what the forward and reverse reactions are. The forward reaction is the conversion of reactants to products, while the reverse reaction is the conversion of products back to reactants. In this case:
Forward reaction: A ⟶ B
Reverse reaction: B ⟶ A
Now, let's calculate the activation energy (Ea) for both the forward and reverse reactions.
For the forward reaction (A ⟶ B), the given Ea is 48 kJ mol⁻¹.
For the reverse reaction (B ⟶ A), remember that the activation energy for the reverse reaction is the same as the activation energy for the forward reaction. So, Ea for the reverse reaction is also 48 kJ mol⁻¹.
Moving on to the reaction enthalpy (ΔrH), we need to identify the reaction equation and sum up the individual reactions.
A ⟶ B: ΔrH = 24 kJ mol⁻¹
B ⟶ C: ΔrH = -12 kJ mol⁻¹
C ⟶ D: ΔrH = -48 kJ mol⁻¹
Now we can sum up the overall reaction by adding up the individual reaction enthalpies:
A ⟶ B ⟶ C ⟶ D
ΔrH total = ΔrH₁ + ΔrH₂ + ΔrH₃
= 24 + (-12) + (-48)
= -36 kJ mol⁻¹
So the overall reaction enthalpy (ΔrH) for the A ⟶ B ⟶ C ⟶ D sequence is -36 kJ mol⁻¹.
Voila! We have solved for Ea (forward and reverse) and ΔrH using the given information. I hope this explanation has been helpful, even if it was a bit of a clown show!
To solve for the activation energy (Ea) in the forward (f) and reverse (r) directions, as well as the reaction enthalpy (ΔrH), we can use the Arrhenius equation and the relationship between ΔrH and reaction steps. The Arrhenius equation relates the rate constant (k) of a reaction to its activation energy and temperature:
k = Ae^(-Ea/RT)
Where:
- k is the rate constant
- A is the frequency factor
- Ea is the activation energy
- R is the ideal gas constant
- T is the temperature in Kelvin
For the forward reaction:
Given ΔrHf (the enthalpy change for the forward reaction A ⟶ B), which is 24 kJ/mol, and Ea,f (the activation energy for the forward reaction B ⟶ C), which is 36 kJ/mol, we can calculate Ea,f using the Arrhenius equation by making use of the fact that the rate constant is related to the forward reaction:
ln (k_f) = ln (A) - (Ea,f / RT)
For the reverse reaction:
Given Ea,r (the activation energy for the reverse reaction C ⟶ B), which is -12 kJ/mol, we can calculate Ea,r using the Arrhenius equation by making use of the fact that the rate constant is related to the reverse reaction:
ln (k_r) = ln (A) - (Ea,r / RT)
By comparing these two equations, we can see that the value of the frequency factor (A) remains the same. Thus, we can set up an equation to solve for A using the given information:
ln (k_f) - ln (k_r) = (Ea,r - Ea,f) / RT
Solving for ΔrH:
Given ΔrHr (the enthalpy change for the reverse reaction C ⟶ D), which is 24 kJ/mol, we can calculate ΔrH by summing the enthalpy changes of the individual steps:
ΔrH = ΔrHf + ΔrHr
By following these steps, you can solve for Ea forward, Ea reverse, and ΔrH using the given information.