[dhoom3]

General Chemistry 2, Little Help needed!
I have 4 problems, which of i have done most of all but number 3. Just stuck here and there in all problems.

                   [  Concentrations (Mol/L)   ]                             [ Mol / L * Sec ]
                   [CH3COCH3]    [Br2]    [H+]                              [Initial Rate]
                         0.30         0.05     0.05                               5.7 X 10^-5
                         0.30         0.10     0.05                               5.7 X 10^-5
                         0.30         0.05     0.10                               12.0 X 10^-5
                         0.40         0.05     0.20                               31.0 X 10^-5
                         0.40         0.05     0.05                               7.6 X 10^-5                         

1) CH3COCH3 + Br2 + H+  :rarrow:CH3COCH2Br + Br-
    a) Determine Rate expression, Give rate order with respect to each reactant as well as the overall rate order.
             What i got -> Rate 3 / Rate 1,  ( 12.0 X 10^-5Mol/L*Sec ) / ( 5.7 X 10^-5Mol/L*Sec )
                                                       = ( K (.30 )^x (.05)^y (.10)^z ) / ( K (.30)^x (.05)^y (.05)^z )
                                                     So, Rate 3/ Rate 1 = 2.1, (close to 2) and (.10 / .05)^z = 2
                                                     So, Z = 2 (Correct?)
                             -> Rate 5/ Rate 1, I get X = 1 (Correct?)
                             -> Rate 2/Rate 1, I get y = 2 (Correct?)

    b) Determine Value for Rate Constant K with correct units.
              What i got -> K = Rate / [CH3COCH3]¹[Br2]²[H+]¹
                                 (Once someone answers and i make sure part a is correct, ill know the part b values)
    c) Determine Initial Rate of reaction When [H+] = .05 M [CH3COCH3] & [Br2] = .10 M
              What i got -> Rate = ( K (from part b) ) (.50M)(.10M)²(.10M)
                                  (Once again, continuing from part b, just need to make sure part b is right)


2) The First order Rate Constant for the reaction A  B has been measured at a series of temperatures:

       K ( s ^-1 )          T ( ^oC )
        10.6                                10
        47.4                                20
        162                                 30
        577                                 40
  -> Determine GRAPHICALLY the activation energy (Ea) for the reaction.
              What i got -> I graphed the points and graph is curve going up. but i just dont know how/where to drive the problem to after that.
                                 If little bone/hint/help tossed here will be appreciated.


Thank you in advance. 

[Astrokel]

Your rate expression is wrong.

Assuming r = k [CH₃COCH₃]^x[Br₂]^y[H⁺]^z

Using data 1&2,

r₁/r₂ = (k [0.30]^x [0.05]^y [0.05]^z) / (k [0.30]^x [0.10]^y [0.05]^z)

You can cancel off pretty much common terms and work with indices and you will realize concentration of Br₂ has no effect on your rate thus it will be 0 order. Try using other datas and work out this way. Otherwise you can determine through observations.

2) A curve? Rearrange your arrhenius' equation to the form of Y = mX + C.

[dhoom3]

a)   i noticed that when i do rate3/rate1  where only [H+] is changed. It has direct effect on Initial Rate. ( .10 / .05 ) = 2   and 12.0 x 10^-5 / 5.7 x 10^-5 = 2.1 (app. 2). Does this mean it has direct affect? means Rate order of z = 1?

When i do rate5 / rate 1, where only [CH3COH3] is changed. .40/.30 = 1.3 ( app. 1 ) and 7.6 / 5.7 = 1.3 (app. 1) . So X = 1?
and
Y, when Br2 is changed it has no effect on initail rate. What would that mean? order = 0?  then what how would i set up to find my constant K,
If y = 0 then would Constant K Equation be   

K = Rate / [CH3COH3]¹[H+]¹ ,   cuz of [Br2]⁰ it would just be canceled correct?


2) hmm.. I think the equation you talking about is, ln K = -(Ea/R) (1/T) + ln A   so ln K = Y, -(Ea/R) = m, (1/T) = x, ln A = B
but i just dont understand the problem i know i have to find slope.. but just dont know how to even start the problem.
Do i just do
Slope = ( 577 - 10.6) / ((40+273) - (10+273)), and multiply that by R?

[Astrokel]

a) is correct.

2) you would have to multiply the gradient by -R. That's only if you are plotting ln K against 1/T and you should get a straight line, no?

[dhoom3]

Amm.. No, im sure i am doing something terribly wrong...

In the book i see one of the problem solved graphically with line going  " \ "   and they collected data from it.. :\ hmm now there is where i get confused. am i just lost or hmmm

What equation(s) i use here?
How would i do this problem.. just lost.