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Topic: calculating rate of reaction  (Read 1718 times)

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Offline shek

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calculating rate of reaction
« on: February 25, 2016, 08:05:04 AM »
I have a question on calculating the average rate of reaction.
Here is the question:
CaCO3+2HCl  :rarrow: CaCl2+CO2+H2O
When 2g of lumps of calcium carbonate was added to 50cm3  of 2M HCl, the CaCO3 reacted and disappear in 120s.

What is the average rate of the whole reaction expressed in terms of rate of consumption of HCl in mol/dm/s?

solution is average rate of consumption =0.0167/(40.1+12+16x3)
=1.67x 10^-4
Average rate of consumption of HCl
=1.67x10^-4X2/0.05
=6.68x10^-3


but why does not it works?
rate of consumption of HCl
=0.01998(no of mol of CaCO3)x2/0.05/120
 I just do it according to the required units in the quedtion but there is errors

Mod Edit: fixed right arrow
« Last Edit: February 25, 2016, 08:01:05 PM by billnotgatez »

Offline Burner

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Re: calculating rate of reaction
« Reply #1 on: February 25, 2016, 09:35:10 AM »
solution is average rate of consumption =0.0167/(40.1+12+16x3)
=1.67x 10^-4
Average rate of consumption of HCl
=1.67x10^-4X2/0.05
=6.68x10^-3


but why does not it works?
rate of consumption of HCl
=0.01998(no of mol of CaCO3)x2/0.05/120
 I just do it according to the required units in the quedtion but there is errors

I got the same result using your two methods so I don't see any errors in your expression. However, I think that step-by-step calculations are better because they are easier to follow and check.
Year 1 science student in HKUST and a Chemistry geek.
If I make any mistakes in the forum, please don't hesitate to correct me as I want to learn.

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