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# Reaction Rate question watch

1. Question attached..

It stumped a load of people in my course last year and I am yet to find a solution. I am terrible at chemistry and it looks very simple. If anyone can help me out and explain the answer i'd be very grateful.

Thank you!
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2. (Original post by jdouglassmith)
Question attached..

It stumped a load of people in my course last year and I am yet to find a solution. I am terrible at chemistry and it looks very simple. If anyone can help me out and explain the answer i'd be very grateful.

Thank you!
Arrhenius equation relates the temperature and the rate constant ...

k = Ae-Ea/RT

The rate of a reaction can be taken as the rate of change of a reactant or product.

You are given the time for shelf life. You could estimate that the rate is inversely proportional to this time.

This would give you comparative values for k which you could then use in the Arrhenius equation.
3. (Original post by charco)
Arrhenius equation relates the temperature and the rate constant ...

k = Ae-Ea/RT

The rate of a reaction can be taken as the rate of change of a reactant or product.

You are given the time for shelf life. You could estimate that the rate is inversely proportional to this time.

This would give you comparative values for k which you could then use in the Arrhenius equation.

I understand but I'm not sure what you would use the comparative values of K for if you plug them into the equation? Would you try estimate a value for activation energy using these variations of K?

So I have estimations of the rate using 1/t:

1/1, 1/7, 1/30 and 1/90?

do i stick this into the equation to estimate activation energy?

Sorry I'm still very confused!
4. (Original post by jdouglassmith)

I understand but I'm not sure what you would use the comparative values of K for if you plug them into the equation? Would you try estimate a value for activation energy using these variations of K?

So I have estimations of the rate using 1/t:

1/1, 1/7, 1/30 and 1/90?

do i stick this into the equation to estimate activation energy?

Sorry I'm still very confused!
Alternatively you could assume 1st order kinetics for the shelf life and apply the formula:

k = 0.693/t

you're gonna need t to be in minutes ...

Then take two values at different temperatures and solve the ln form of the Arrhenius equation simultaneously to get Ea

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