Acids and bases

[Miya Eberlein 1J]

how can we tell if an acid is weak or strong?

[vidish]

A strong acid would completely ionise in water, however which acids would do that you could memorise the names of the six strong acids we are supposed to know.

hydrochloric acid HCl
hydrobromic acid HBr
hydroiodic acid HI
sulfuric acid H2SO4
nitric acid HNO3
perchloric acid HClO4

Every other acid would be considered a weak acid.

[Richard_4E]

A strong acid must be able to lose the hydrogen ion easily.
In addition the weaker or longer the A-H bond is, the easier it is for H20 to remove the H+ and the more acidic something is.
For example HI is more acidic than HCl which is more acidic than HF since HI has longer(weaker) bonds than HCl.
Also for oxo acids like HClO4, the more oxygens it contains, the more acidic it is.
For example, HClO4 is more acidic than HClO2