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Topic: Reaction and product question  (Read 1621 times)

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Offline Pika007

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Reaction and product question
« on: March 28, 2014, 08:07:57 AM »
Hi
I recently got the following question, for some reason i can't seem to get the correct answer-

"For 25g of each of the following reactants, how many grams of CrSO4 will result?

4Zn + K2Cr2O7 + 7H2SO4 ---> 4ZnSO4 + 2CrSO4 + K2SO4 + 7H2O

I tried it twice and got either 12.6 or 25.2
Both answers are wrong, i can't figure out why. Any help would be much appreciated

Offline Borek

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Re: Reaction and product question
« Reply #1 on: March 28, 2014, 08:20:48 AM »
Show how you got these numbers.
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Offline Pika007

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Re: Reaction and product question
« Reply #2 on: March 28, 2014, 08:48:07 AM »
K2Cr2O7 is the only reactant on the right hand side that contains Cr, 25g of it at molar weight of 294.18 are 0.085 moles

On the left hand side Chromium is present only as 2CrSO4
I should still only have 0.085 moles of Cr2 (or 0.17 as Cr)
0.085*148.06(molar weight of CrSO4)=12.58 or ~12.6

This should be right by conservation of mass, and this way has also worked for other similar questions. I'd be glad to know what went wrong

Offline Borek

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Re: Reaction and product question
« Reply #3 on: March 28, 2014, 08:59:43 AM »
« Last Edit: March 28, 2014, 04:29:09 PM by Borek »
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Offline Pika007

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Re: Reaction and product question
« Reply #4 on: March 28, 2014, 03:36:38 PM »
Yeah, but this specific sheet wasn't supposed to have any. Obviously, this isn't the case....
I'll factor it in and try to see if i reach the correct answer, thanks

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