i need help with chemistry kinetics problems?

Question

how do you do these? o_O i tried to do it a few times and i kinda got stuck.

A + 2 B => 3 C + D
Experiment 2 : A0 = 0.240 M, B0 = .120M, Initial rate of reaction = 2.00 M/h
2d. Assume that the reaction goes to completion. Under the conditions specified for experiment 2, what would be the final molar concentration of C?
I found the rate law equation to be: rate = 603 [A]^2[B]^2
how do you do this problem? o_O i don't think i understand the wording too much.

3b. Partial Pressure of A as a function of time at 100 C.
PA (mm Hg) ;; t (sec)
348 ;; 0
247 ;; 600
185 ;; 1200
105 ;; 2400
58 ;; 3600
Describe, without doing any calculations, how graphs can be used to determine whther this reaction is first or second order in A and how thse graphs are used to determine the rate constant.
what?! ._. we worked with rate laws and stuff, but not with pressures. is it the same as when you're working w/ T & rates?

please help me. ._. i understand it, but the wording is just... out there... thanks! :]

Answer 1

For the first question , the key words are FINAL MOLAR CONCENTRATION. This assumes that the reaction has gone to completion and kinetics are no longer involved. Since the balanced reaction is A + 2B ---> 3C, you can determine that the limited reagent is "B" and that "C" is created at a 2:3 ratio. At the end of the reaction there will be 0.180M in "C" since is was created in a 2:3 ratio starting with 0.120M "B".

As for the second question, graphs can be used to determine if the reaction kinetics are first order or second order. If you make a graph plotting the natural log of the pressure of "A" versus time ( ln(A) vs. t ), and you get a straight line graph, then the reaction will be exhibiting first order kinetics. If you make a graph plotting the inverse of the pressure of "A" versus time ( 1/(A) vs. t ) and you get a straight line graph, then the reaction will be exhibiting second order kinetics.