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### determine K

Posted: **Wed Mar 07, 2018 9:16 pm**

by **Ekayana Sethi 2K**

For the first-order reaction A -->3 B +C, when [A]o is

0.015 mol!L"1 , the concentration of B increases to 0.018 mol!L"1

in 3.0 min. What is the rate constant for the reaction expressed

as the rate of loss of B?

### Re: determine K

Posted: **Wed Mar 07, 2018 10:27 pm**

by **sofiakavanaugh**

I think this is one were you first have to find [A]t. To do this you first write the increase in [B] in terms of [A], which means you need to multiply mol B/L x (1 mol A/3 mol B). Then you take your [A]o and subtract the number you just calculated from it. Since its first order, you use the integrated rate law ln[A]t=-kt + ln[A]o, plug in the number you just calculated for [A]t, your time is 3 min, and you also are given [A]o, and then rearrange the equation to get k. Note, make sure your units of k are correct, if they ask for it in seconds you may need to convert.

Hope this helps.

### Re: determine K

Posted: **Wed Mar 07, 2018 11:57 pm**

by **Ekayana Sethi 2K**

yes I know how to calculate in terms of A but what about in terms of B?

### Re: determine K

Posted: **Tue Mar 13, 2018 7:27 pm**

by **mayapartha_1D**

Because there are 3 moles of B and only one of A it should be the same process just use the equation that would include 1/3!