I had to make a graph using lnK vs 1/T and find the slope. The slope was -1.23e4 and now I have to find Ea.
Do I divide the slope by R
slope = -Ea/R
I did -1.23e4 / 8.314 = -1479.43
and I tryed 1.23e4 / 8.314 = 1479.43 but my online homework keeps saying that its incorrect.
Nevermind I know what I did wrong. I had to divide my final answer by 1000 to get kJ.
To calculate the activation energy (Ea), you can use the Arrhenius equation:
lnK = -Ea/RT + ln(A)
Where:
- K is the rate constant
- Ea is the activation energy
- R is the gas constant (8.314 J/(mol·K))
- T is the temperature in Kelvin
- A is the pre-exponential factor or frequency factor
In your case, you have already determined the slope (-1.23e4) of the lnK vs. 1/T graph. The slope is equal to -Ea/R, so you need to multiply the slope by R in order to find Ea.
Ea = slope × R
= (-1.23e4) × (8.314 J/(mol·K))
Make sure to use consistent units for R and the slope to get the correct result for Ea. The units of R are J/(mol·K), so the resulting unit for Ea will be Joules (J).
However, if you want the answer in kilojoules (kJ), you can convert the result from J to kJ by dividing by 1000:
Ea (in kJ/mol) = (Ea in J)/(1000 J/kJ)