Strong/Weak acids and bases (1 Viewer)

[Lucas_]

When asked if an acid is a strong or weak is there a way we can "determine" this or do we just have to memorise which are which?

Example:
1. Classify the following as strong acids or weak acids:
a) HCL
b) H₂CO₃
c) H₂SO₄
d) H₃PO₄
e) CH₃COOH

2. Classify the following as strong or weak bases:
a) NaOH
b) NH₄OH
c) KOH

Thanks

EDIT: I have researched all of these answers but i'm still curious if there is a way. I'm thinking it has to do will the level of dissocation in water.

 

[nightweaver066]

Strong acids are acids that completely dissociate in to its ions in solution.

Weak acids are acids that partially dissociate in to its ions in solution.

All organic acids are weak acids.

Similar for bases.

In strong acids, the anion tends to be composed to a very electronegative element, e.g. Cl-, SO4(2-), NO3-

1. a) S
b) W
c) S
d) W
e) W

2. a) S
b) W
c) S

 

[bleakarcher]

Strong acids are acids that completely dissociate in to its ions in solution.

Weak acids are acids that partially dissociate in to its ions in solution.

All organic acids are weak acids.

Similar for bases.

In strong acids, the anion tends to be composed to a very electronegative element, e.g. Cl-, SO4(2-), NO3-

1. a) S
b) W
c) S
d) W
e) W

2. a) S
b) W
c) S

i iz confused?

 

[nightweaver066]

i iz confused?

*Most are (all organic acids i've encountered were all weak so far).

 

[kingkong123]

*Most are (all organic acids i've encountered were all weak so far).

*all organic acids are weak (don't ionise 100%)

 

[rolpsy]

In general, most acids are weak, however you should know that:
hydrochloric (HCl),
nitric (HNO₃),
sulfuric (H₂SO₄),
hydrobromic (HBr), and
hydroiodic (HI)
acids are all strong.

Strong bases you should know: NaOH, KOH, LiOH, RbOH, and CsOH.


A combination of electronegativity & the size of the ion attached to the hydrogen (i.e. the conjugate base) determine whether it is a strong/weak acid. (This explains why hydrofluoric acid (HF) is weak – the fluoride ion is tiny, making it unstable.)

edit: I should probably clarify. The strength of an acid depends on the stability of its conjugate base.

*all organic acids are weak (don't ionise 100%)

Triflic acid is an organic acid and one of the strongest acids known (as a side note it is used for catalysis of esterification)
...
but yes almost all organic acids are weak.

 

[Kimyia]

When asked if an acid is a strong or weak is there a way we can "determine" this or do we just have to memorise which are which?
EDIT: I have researched all of these answers but i'm still curious if there is a way. I'm thinking it has to do will the level of dissocation in water.

Yes, strong acids/bases ionise 100% while weak acids/bases only partially ionise.
As to which is strong and which is weak if your just given a formula and no other information, I think it just comes down to recognising whether its strong or weak from memory.

 

[Lucas_]

Thank you all for your responses

 

[xDarkSilent]

strong acids are normally laboratory acids

and

weak acids are normally household acids

(also another way to remember them)

 

[eshay lad 69]

the taste test is a classic way of testing and has never failed me.

 

[Shadowless]

the taste test is a classic way of testing and has never failed me.

+1

 

[xDarkSilent]

LOL ^