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Topic: Rate of reaction on temperature and surface area  (Read 5221 times)

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Offline Au197

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Rate of reaction on temperature and surface area
« on: May 27, 2012, 07:10:37 AM »
I have a chemistry report to do on the rate of reaction on Berocca tablets. The problem I'm having is with the data.

Firstly

1 tablet in 23 degrees disolves in 250 seconds
Halves in 175 seconds
quarters in 158 seconds
and powdered in 39 seconds to completely disolve.

The temperature is fine, I'm getting more than double the rate with 2.8 times the temperature.

But looking at the surface area I can't understand why, with Halves you have an extra 350mm2 surface area, and with quarters you have an extra 800mm2 surface area. So why is the rate of reaction significantly more between 1 and halves, than it is for halves and quarters?

Part 2 of the question, does the amount of water affect the rate of reaction over time. I understand there must be a saturation point in which the water may not take any more of the powder in. So does this rate of reaction slow down as more of the tablet is being introduced to the water?

Offline Wald_ron

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Re: Rate of reaction on temperature and surface area
« Reply #1 on: May 27, 2012, 05:44:34 PM »
Maybe , when you cut it in half, you are roughing up the edges more than you think.

If you want, try 4 tablets compared to 2
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Offline fledarmus

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Re: Rate of reaction on temperature and surface area
« Reply #2 on: May 29, 2012, 10:08:10 AM »
As Wald_ron indicates, you are making the implicit assumption that the surface you create when you split the tablets is identical to the surface of an uncut tablet. What happens if you change your analysis to account for two different types of surface?

Offline Au197

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Re: Rate of reaction on temperature and surface area
« Reply #3 on: June 04, 2012, 08:02:09 AM »
Thanks guys, they told me not to worry about it, just to report that there was a change

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