reaction rates question

[mangos]

how would you approach a question like this mathematically? i remember doing question like this in my phys lab final but i forget how to now

 

so the question only gives you the reactant concentraton A which as 2 trials of the same [A]. however, for , all the trails have different .

 

as such, finding the order of reaction of B is easy since i can elimante two trials of A.

 

however, how do i find the order of A then since none of the trials for B have 2 of the same concentrations?

 

thanks

[thehumanmacbook]

sorry this is off my phone but usually they will be factors or powers (X cubed) and you can take that into account accordingly in your constant calc.

[Tangy]

Okay let's use a table:

 

Reaction Rate--------A-------------- B

10 ------------------1---------------1

20------------------ 1---------------2

20------------------1/2 -------------4

 

(I really hope the above is not flawed and I hope I understood your question).

 

You can easily find B, but it's a bit tougher to find A.

 

To find B, keep A constant (so experiment 1 and 2), you notice that B increases by a factor of 2 and the reaction rate also increases by a factor of 2. Thus is to the power of 1.

 

Now for [A], you need to keep in mind that the reaction rate is linearly proportional to the reaction rate. Thus from experiment 2 to 3, you notice that A decreases by a factor of 2. B increases by a factor of 2. If we only took B into account, then reaction rate should have increased by 2. But it stayed the same. Thus the reaction rate must also be linearly proportional to A, because A decreased by half. To prove this, let's consider experiment 1 and 3. A decreases by half, and B increases by a factor of 4. One would expect that the reaction rate increases by a factor of 4 (from 10 to 40). But instead, it is only doubled. Thus, the decrease in A (by 2) also decreased the reaction rate by 2. Thus, the reaction rate is proportional to [A]^1 times ^1.

 

Hope that was helpful

[bored]

Okay let's use a table:

 

Reaction Rate--------A-------------- B

10 ------------------1---------------1

20------------------ 1---------------2

20------------------1/2 -------------4

 

(I really hope the above is not flawed and I hope I understood your question).

 

You can easily find B, but it's a bit tougher to find A.

 

To find B, keep A constant (so experiment 1 and 2), you notice that B increases by a factor of 2 and the reaction rate also increases by a factor of 2. Thus is to the power of 1.

 

Now for [A], you need to keep in mind that the reaction rate is linearly proportional to the reaction rate. Thus from experiment 2 to 3, you notice that A decreases by a factor of 2. B increases by a factor of 2. If we only took B into account, then reaction rate should have increased by 2. But it stayed the same. Thus the reaction rate must also be linearly proportional to A, because A decreased by half. To prove this, let's consider experiment 1 and 3. A decreases by half, and B increases by a factor of 4. One would expect that the reaction rate increases by a factor of 4 (from 10 to 40). But instead, it is only doubled. Thus, the decrease in A (by 2) also decreased the reaction rate by 2. Thus, the reaction rate is proportional to [A]^1 times ^1.

 

Hope that was helpful

 

 

But he said the concentration of A for both trials stays the same..

let me give this a try, (though it would be easier if you provide the table).

 

Reaction Rate--------A-------------- B

10 ------------------10---------------10

20------------------ 10---------------20

 

Rate = k [a]x y --> ntoe x and y are exponents.. im not gonna use the stupid ^ symbol

 

use the first rate..

10 = (10)^x (10) ^ y

20 = (10)^x (20) ^ y

 

devide these two equations..

 

1/2 = (1/2) ^ y, so now you know that y = 1..

now place this y into one of the equations..

 

10 = k(10)^x (10)^y

10 = k(10)^x (10)^1

1 = k(10)^x

 

k well that doesnt work.. you will just have to play around with numbers and try to find k or eliminate it.. cause if the concentration of A does not change, than you cant follow the systematic way.