Which of these is the strongest acid? #"HCl"#, #"H"_3"PO"_4#, #"CH"_3"COOH"#
2 Answers
The highest
#"HA"(aq) + "H"_2"O"(l) rightleftharpoons "H"_3"O"^(+)(aq) + "A"^(-)(aq)# (note that
#"H"_3"O"^(+)# and#"H"^(+)# are different representations for equivalent species.)
By definition, a strong acid dissociates pretty much completely, so it must give the most
This can be quantified by their acid dissociation constants,
#"HCl"# :#K_a ~~ 10^7#
#"H"_3"PO"_4# :#K_(a1) = 6.9 xx 10^(-3)#
#"CH"_3"COOH"# :#K_a = 1.76 xx 10^(-5)#
Based on the values of the
Because
Explanation:
When we talk of the strength of an acid, we refer to the following equilibrium reaction in water:
The further the equilibrium lies to the right hand side as we face the page, the STRONGER is the acid. (Sometimes we represent
For the LOWER hydrogen halides,
For acetic acid and phosphoric acid, the equilibrium would not go to completion:
Mind you phosphoric acid has a lower