strong and weak acids

sqrt of 5

19

I really don't understand this question 😭😭

Reply 1

username3249896

12

e.g pH of 0.001 mol dm^-3 HCl = 3
pH of 1 mol dm^-3 CH3COOH (pKa = 4.76) = 2.4

Reply 2

sqrt of 5

OP

19

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?

Reply 3

Pigster

20

Original post by sqrt of 5

I really don't understand this question 😭😭

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.

Reply 4

username2703735

18

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.

Reply 5

sqrt of 5

OP

19

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.

(edited 5 years ago)

Reply 6

damnit1

9

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

Reply 7

sqrt of 5

OP

19

now i understand @BobbJo's example! Can i also use that one to answer the question?

Reply 8

sqrt of 5

OP

19

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?

(edited 5 years ago)

Reply 9

damnit1

9

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

Reply 10

thotproduct

19

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.