Activation Energy formula

In summary, to find the activation energy for water boiling in different altitudes, you can use the equation Ea=-R(ln k2/k1)[(1/T2)-(1/T1)]^-1 and rearrange it to solve for Ea. The variables needed are T2, T1, time1, time2, and R, while the variables given in the problem are T2=363.0K, T1=372.0K, time1=336s, time2=270s, and R=8.314 J/mol*k. After plugging in the values and solving, the calculated activation energy is 27000 J/mol. However, the answer should be checked for potential roundoff errors and all
  • #1
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Homework Statement



In Houston (near sea level), water boils at 100.0°C. In Cripple Creek, Colorado (near 9500 ft), it boils at 90.0°C. If it takes 5.6 min to cook an egg in Cripple Creek and 4.5 min in Houston, what is Ea for this process?What I do not understand is how I can figure this when the given formula for find Ea involves 2 unknown rate constants, and the formula for finding the rate constant given involves concentrations? So, how can I find the activation energy when given only 2 temperatures and 2 times?

Homework Equations



ln(k2/k1)=(-Ea/R)[(1/T2)-(1/T1)]^-1

k=rate1/(concetrations)

The Attempt at a Solution



Not sure where to start...
 
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  • #2
well, you have an equation for Ea... rearrange it to solve for Ea.

What variables do you know? What variables do you need?

hint: you might not have to solve for each k value individually
 
  • #3
dmoravec said:
well, you have an equation for Ea... rearrange it to solve for Ea.

What variables do you know? What variables do you need?

hint: you might not have to solve for each k value individually

Ea=-R(ln k2/k1)[(1/T2)-(1/T1)]^-1

Ea=?
T2=363.0K
T1=372.0K
time1=336s
time2=270s
R=8.314 J/mol*k

Do I plug in the times for k? I am attempting it now, it looks as if it should still all cancel and leave me with J/mol which I want...
 
  • #4
Ok, I came up with 27279.97791 J/mol corrected to 27000 J/mol for sig figs, but Webassign says I am wrong, and within 10% of the correct answer. "Your answer is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error."Edit: I wrote a temp incorrectly in my conversion. Correct now!
 
Last edited:

1. What is the Activation Energy formula?

The Activation Energy formula is a mathematical equation that represents the minimum amount of energy required for a chemical reaction to occur. It is denoted as Ea and is typically measured in kilojoules per mole (kJ/mol).

2. How is the Activation Energy formula used in science?

The Activation Energy formula is used to calculate and understand the rate of a chemical reaction. By knowing the amount of energy required for a reaction to take place, scientists can predict the speed and efficiency of the reaction.

3. What are the variables in the Activation Energy formula?

The variables in the Activation Energy formula include the rate constant (k), the temperature (T), and the Arrhenius constant (A). These variables are used to determine the activation energy (Ea) of a reaction.

4. How is the Activation Energy formula derived?

The Activation Energy formula is derived from the Arrhenius equation, which relates the rate constant of a reaction to the temperature and activation energy. By rearranging the equation, the Activation Energy formula can be obtained as Ea = -RT ln(k/A), where R is the gas constant and T is the temperature in Kelvin.

5. Can the Activation Energy formula be used for all chemical reactions?

No, the Activation Energy formula is specific to each chemical reaction and cannot be applied universally. The value of Ea varies depending on the reactants and conditions of the reaction. Additionally, some reactions may not have a well-defined activation energy.

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