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Topic: Acids and Bases  (Read 4777 times)

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Offline Meowmix88

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Acids and Bases
« on: February 22, 2011, 06:48:59 PM »
IF the auto-protolysis (kw) constant of water is 10 degrees C is 2.93X10^-15, what would the pH of pure water be at 10 degrees celcius. Will it be acidic or Basic? Briefly explain


Calculate the pH of a 1.0 X 10^8 solution of HCL. Hint: Think carefully about this one. Consider all the sources of hydronium. Explain briefly your result.


Please give detailed answers or just help explain it beacuse i'm utterly confused!!!!!!

Offline Schrödinger

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Re: Acids and Bases
« Reply #1 on: February 23, 2011, 02:06:06 AM »
First question : Auto protolysis of water : H2O + H2::equil:: H3O+ + OH-

Write the equilibrium expression for this equation. Then find the concentration of H3O+.
Use pH = -log{[H3O+]}


Second question : In this question, not only do you need to consider the dissociation of HCl, but also the dissociation of water (as in the first question), since the concentration of HCl is extremely low. Using both these dissociation equations, find the hydronium ion concentration, and then pH.


Hope this helps :)
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Offline Borek

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Re: Acids and Bases
« Reply #2 on: February 23, 2011, 04:54:22 AM »
what would the pH of pure water be at 10 degrees celcius. Will it be acidic or Basic?

Can pure water be acidic or basic?
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Offline 13dente

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Re: Acids and Bases
« Reply #3 on: February 23, 2011, 01:29:33 PM »
what would the pH of pure water be at 10 degrees celcius. Will it be acidic or Basic?

Can pure water be acidic or basic?

Carefull with the expression pure water. What you mean with this? Ultrapure, desmineralized, distilled, potable are some types of water...
The pH of the solution varies with the temperature. This may be due the absorption of carbon dioxide to the solution, so the pH of the "pure" water could be slightly acidic or basic.

Offline Borek

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Re: Acids and Bases
« Reply #4 on: February 23, 2011, 01:35:58 PM »
Carefull with the expression pure water. What you mean with this? Ultrapure, desmineralized, distilled, potable are some types of water...

From the way question is worded it is obvious it wants the OP to ignore everything else but water - so for now I would settle for ultrapure.
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