December 14, 2019, 01:03:38 AM
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Topic: Chemical kinetics  (Read 168 times)

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Offline INeedSerotonin

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Chemical kinetics
« on: November 10, 2019, 05:26:44 PM »
Consider the propositions below, and take into consideration that they refer to a first order unimolecular reaction.

I - the rate of reaction varies linearly with the concentration of the reagent
II - the instantaneous rate is an exponential function of time
III - the half-life of the reagent depends on its initial concentration

Which of these are correct?

Answer: (I) and (II)

I have no clue. I thought that the answer was (I) and (III).

I think that (I) is correct because V = K . [Reagents]. I have no idea why "the instantenous rate is an exponential function of time", and I swear I learnt half-life as Initial Concentration / 2^t.

Can you guys give me some hints here?

Thanks

Offline AWK

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Re: Chemical kinetics
« Reply #1 on: November 10, 2019, 06:11:08 PM »
It's worth reading on Wikipedia about the "rate equation".
AWK

Offline mjc123

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Re: Chemical kinetics
« Reply #2 on: November 11, 2019, 08:23:46 AM »
Quote
I have no idea why "the instantenous rate is an exponential function of time"
What is the integrated  rate equation for a first-order reaction?
Quote
I swear I learnt half-life as Initial Concentration / 2^t.
That's nonsense; half-life is not a function of time.
Maybe what you learnt was Concentration = Initial concentration/2^(t/τ) where τ is the half-life. This is related to the answer to my first question.

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