half life problem

[tissy]

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I get some of these problems wrong...Can someone explain this..

What is the value of the rate constant for a first order reaction that has a half like of 1.5 hours?

Number 54 on topscore..don't understand the solution

 

[lifeisgood]

When you are talking about exponential decay (i.e. half-life problems) remember that the rate constant λ is related to the half life by the following equation:

λ = ln 2/(half-life)

You should know that ln 2 = 0.693. So all the problem is asking is what is 0.693/1.5, or better yet which of the answer choices multiplied by 1.5 will give you 0.693. The answer is obviously A.

Hope this helps.

 

[lifeisgood]

See Kaplan Blue Book p 319 top of the page and you'll see what I am talking about.

 

[tissy]

See Kaplan Blue Book p 319 top of the page and you'll see what I am talking about.

Thanks...