# 2004 - Written Paper - Q8(b)

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### #1jamiep

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Posted 30 May 2005 - 04:13 PM

Q8b : Calculate the concentration of hydroxide ions in the 1mol l-1 HCl acid used in the experiment.

I do not understand why the concentration of H+ ions is 1x10 0 so the answer is 1x10 -14 mol l-1.

Anyone?

### #2dfx

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Posted 30 May 2005 - 04:21 PM

The total is always 1 x10^-14 So if the concentration of OH is 1 x 10^0, consequently the concentration of H+ ions will be 1 x 10^-14.

### #3YIC

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Posted 30 May 2005 - 04:23 PM

In scientific notation, 1 = 10^0, 0.1 = 10^-1, 0.01 = 10^-2 , etc.
1 mol / litre = 10^ 0 mol / litre because there are no 0's before the 1. Therefore, the conc. is 10 ^ -14. (Just think of the powers having to add together to give -14, so if you have 10 ^ -2 the other one has to be 10 ^ -12)

I hope you understand now

### #4Tiger

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Posted 30 May 2005 - 04:24 PM

pH=-log[H+]
[H+]=1
Therefor pH=-log[1]=0
So [OH-]=1 x 10^-14

Hope thatz right.

### #5jamiep

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Posted 30 May 2005 - 04:29 PM

*Lightbulb*

Thanks for that guys, especially YIC, very clear!

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