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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: Firehchicken on January 29, 2018, 09:56:20 PM

Title: Question on rate of reaction
Post by: Firehchicken on January 29, 2018, 09:56:20 PM

Hi, the correct answer is E) for the question in the picture.

I am at loss here, my choice was B) since the coefficients match stoichiometrically when comparing the expression and the reaction..???

I emailed my professor, now he is saying the correct answer is C). whereas the mark scheme clearly says E) is the correct answer.

Title: Re: Question on rate of reaction
Post by: Borek on January 30, 2018, 02:43:46 AM

I am before my coffee, but I would go with B as well.

Title: Re: Question on rate of reaction
Post by: mjc123 on January 30, 2018, 04:45:09 AM

Did you read my post in http://www.chemicalforums.com/index.php?topic=94029.0?
I said there:
"Rate = (1/α)*d[X]/dt
where α is the coefficient of reagent X in the equation (negative for reactants, positive for products)."
So you divide by the coefficient, not multiply. (And the coefficients in B don't match the equation - they are multiplied by 2. And "rate of reaction" means "of the reaction as written". So the rate of the reaction 2A  :rarrow: 2B is twice the rate of the reaction A  :rarrow: B.)
Thus the correct answer is C. Mark schemes may make errors.