Anyone familiar with the Arrhenius equation?

[Melchiah]

I can't seem to come up with the same answer as the book for this problem, and I don't understand where I am going wrong. I am asked to determine the rate of reaction given a balanced equation, a Temperature, and some experimental values:

The Arrhenius equation: k = Ae^-(Ea/RT)

The reaction in question is a decomposition reaction, therefore it is First Order and has a rate law of rate = k[B]

Ea = 221 kJ/mol; A = 1.2E14/s; R = 8.314 J/(mol*K); T = 673 K; [B] = .012 mol/L

By the Arrhenius equation: k = 1.2E14/s * (e^-(221 kJ/mol *1000J/kJ * molK/8.314J * 1/673K))

Simplifying the exponent: -(221000/5595.322) = -39.497 (all units cancel in the exponent)

Rewrite the Arrhenius equation: k = 1.2E14/s * e^-39.497

Simplify again: k = 1.2E14/(e^39.497)s

Divide: k = 8.43E-4/s

Substitute back into rate law: rate = 8.4E-4/s * .012 mol/L

rate = 1.01E-5 mol/L s

Now, this answer is in the correct units for a reaction of first order, and compares with the units in the answer section. However, the numerical value the book shows for the rate of reaction is 8E-4 mol/Ls, which is approximately the value I solved k for. So my question is, if anyone here can follow the algebra, have I worked this correctly and did whoever wrote the answer section in the book just not apply k to the rate law, or have I blundered somewhere?

[Enkidu]

Can you post the exact question with the balanced equation and any other information given?

[Melchiah]

Reaction: CH3CH2I --> CH2CH2 + HI

Frequency Factor A = 1.2 x 10^14 s^-1

Activation Energy Ea = 221 Kj/mol

Temp = 673 K

Gas constant R = 8.314 J/molK

Molarity [M] of reactant = 0.012 mol/L

Arrhenius Equation: k = Ae^-(Ea/RT)

The question is to determine the rate of reaction given these data. The type of reaction can be inferred to be a decomposition of one molecule into its parts, therefore it is first order, and the rate law is rate = k[M]

[Kaylia]

School books are often wrong (2-5% of the problem are on higher level stuff). I must spend 5h a week wasting my time trying to understand physics/maths problems that didnt have the correct answer. It's really annoying.

Havent done chemistry in years, but if you can answer another problem like this, chance is the book is wrong, not you.

[Penthesilea]

Can't tell you how many times I've done chem problems and have been flustered and frustrated only to get an email from the professor a few days later saying that the books answers were wrong. Everything looks good on your end, just pick up some non-assigned problems that cover the same topic and do those.

[Ohemgee]

You're right with your algebra. Which book is this?

And I hated Gen. Chem, I don't think Arrhenius is on the MCAT at all. Ehhh

[Melchiah]

Chemistry: The Molecular Science 3rd Edition; Moore, Stanitski and Jurs

[Ohemgee]

High School I'm assuming. I had this black purple book that I never opened.

[Melchiah]

CH-117, General Chem II, UAB

[Ohemgee]

UAB? D:

Yeah well, I did that shit 2 years ago. Sad that I still remember it, even after the PCAT's.

[Melchiah]

http://main.uab.edu/

[Ohemgee]

http://www.nova.edu/

[ozz]

http://www.nova.edu/

my highschool's across the street from you :[

[Ohemgee]

http://www.nova.edu/

my highschool's across the street from you :[

McFatter or Nova? I hate you both, you and your buses.