September 22, 2020, 08:38:13 AM
Forum Rules: Read This Before Posting

### Topic: Chemical kinetics  (Read 326 times)

0 Members and 1 Guest are viewing this topic.

#### INeedSerotonin

• Full Member
• Posts: 165
• Mole Snacks: +1/-0
• I want to learn chemistry.
##### 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

#### AWK

• Retired Staff
• Sr. Member
• Posts: 7522
• Mole Snacks: +525/-88
• Gender:
##### Re: Chemical kinetics
« Reply #1 on: November 10, 2019, 06:11:08 PM »
It's worth reading on Wikipedia about the "rate equation".
AWK

#### mjc123

• Chemist
• Sr. Member
• Posts: 1775
• Mole Snacks: +252/-11
##### 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.