# strong and weak acids

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#1

I really don't understand this question ðŸ˜­ðŸ˜­
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1 year ago
#2
e.g pH of 0.001 mol dm^-3 HCl = 3
pH of 1 mol dm^-3 CH3COOH (pKa = 4.76) = 2.4
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#3
(Original post by BobbJo)
e.g pH of 0.001 mol dm^-3 HCl = 3
pH of 1 mol dm^-3 CH3COOH (pKa = 4.76) = 2.4
O_0' in simple words?
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1 year ago
#4
(Original post by sqrt of 5)

I really don't understand this question ðŸ˜­ðŸ˜­
Strong acids fuly ionise, whereas weak acids only partially ionise. Imagine a strong acid solution with only one acid molecule in it - you will only be able to have one ionisation take place and therefore only produce 1 H+ (which is what makes it acidic). Now consider a weak acid solution with 1000 acid molecules in it; if only 1 in 100 molecules ionise, then you've got yourself 10 H+ ions and it is therefore more acidic. The difference is, the weak acid has more acid molecules per unit volume, i.e. a higher concentration. Shazzam.
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1 year ago
#5
Strong acids will fully dissociate whereas weak acids only partially dissociate
Therefore a concentrated solution of a weak acid will dissociate less (release less) H+ ions than a dilute solution of strong acid.
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#6
(Original post by VMD100)
Strong acids will fully dissociate whereas weak acids only partially dissociate
Therefore a concentrated solution of a weak acid will dissociate less (release less) H+ ions than a dilute solution of strong acid.
(Original post by Pigster)
Strong acids fuly ionise, whereas weak acids only partially ionise. Imagine a strong acid solution with only one acid molecule in it - you will only be able to have one ionisation take place and therefore only produce 1 H+ (which is what makes it acidic). Now consider a weak acid solution with 1000 acid molecules in it; if only 1 in 100 molecules ionise, then you've got yourself 10 H+ ions and it is therefore more acidic. The difference is, the weak acid has more acid molecules per unit volume, i.e. a higher concentration. Shazzam.
i get your point, but the question also mentions the ph which is the thing that i dont understand.
Last edited by sqrt of 5; 1 year ago
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1 year ago
#7
(Original post by sqrt of 5)
i get your point, but the question also mentions the ph
pH is the measure of the amount of H(+) ions (pH literally stands for Potential of Hydrogen). Strong acids ionise completely, so the more H(+) ions are available therefore the pH will be closer to 1
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#8
now i understand BobbJo's example! Can i also use that one to answer the question?
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#9
(Original post by damnit1)
pH is the measure of the amount of H(+) ions (pH literally stands for Potential of Hydrogen). Strong acids ionise completely, so the more H(+) ions are available therefore the pH will be closer to 1
ok so strong acids have a low ph compared to weak acids because the acids particles don't full dissociate to release h+ ions. right?
Last edited by sqrt of 5; 1 year ago
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1 year ago
#10
Therefore you could have lots of a dilute acid, but because they don't ionise completely, not all the H+ ions are available as they're still part of bonds, this means there are less H+ ions so the pH will be less acidic. Whereas in strong acids the H+ ions dissociate completely, so all the H+ ions are available so the pH is more acidic. After all, acids dissolve in water to produce H+ ions
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1 year ago
#11
Consider the ionisations of both strong and weak acids. A strong acid, by definition will completely ionise, and a weak acid will establish an equilibrium and partially ionise. The strong acid, even whilst more dilute than the concentrated weak acid, will still ionise to produce more H+ ions, or a larger concentration if you will, which, again by definition is how pH is quantised (-log[H+]), larger concentration of H+, lower pH, more acidic, coolio.
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1 year ago
#12
(Original post by sqrt of 5)
ok so strong acids have a low ph compared to weak acids right?
Yes, exactly. Also a key fact for GCSE AQA is carboxlyic acids are weak acids - whereas the main HCl, H2SO4 and HNO3 are strong acids
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#13
(Original post by damnit1)
Yes, exactly. Also a key fact for GCSE AQA is carboxlyic acids are weak acids - whereas the main HCl, H2SO4 and HNO3 are strong acids
carbo whaaaaaaaaaaaaaaaaaaaaaaaat? you mean citric acid, ch3cooh and carbonic acid?

Now I fully understand this question! Thank you all
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1 year ago
#14
(Original post by sqrt of 5)
carbo whaaaaaaaaaaaaaaaaaaaaaaaat? you mean citric acid, ch3cooh and carbonic acid?

Now I fully understand this question! Thank you all
Chemicals with the 'COOH' functional group I think, but I'm getting ahead of myself.
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