strength of acid

Question

1st statement:
Pure sulphuric acid is strong acid.
2nd
Pure sulphuric acid completely ionizes in water.

Why both statements are WRONG?

Answer 1

1st statement:

It is WRONG. PURE sulphuric acid means that it does not contain any WATER. Acid has to be ionized in water before it can exhibit ACIDIC PROPERTIES. So it cannot be regarded as an acid. (sulphuric acid is just the name only).

Note: for hydrogen chloride, it is NOT an acid too. Only if it ionizes in water, then it will become hydrochloric acid to exhibit acidic properties.

2nd statement:

It is also WRONG. Pure sulphuric acid does not completely ionizes in water. The ionization is a reversible action. At the end, both sulphuric acid molecules, H+ ions and SO4 2- ions exists. It is worth to note that the concentration of H+ ions is very high. So sulphuric acid is a strong acid

2006-12-27 20:44:58 補充：
Another way of explaining:Pure sulphuric acid and nitric acid are colourless liquids. They both consist of covalent molecules. (NOT IONIC) They do not show acidic properties because no hydrogen ions are present. But when they dissolve in water, IONS are formed

Answer 2

1st statement:
Pure sulphuric acid is strong acid.
No matter pure or not, sulphuric acid H2SO4 is a strong acid, that means it can completely ionized in dilute aqueous solution. The statement is correct.
2nd
Pure sulphuric acid completely ionizes in water.
The complete ionization has relation with concentration. It is impossible for a 98% H2SO4, the most concentrated H2SO4, to ionized completely in this concentration. But in a fairely dilute solution, H2SO4 completely ionized according to : H2SO4 ---> H+ + HSO4-
The 2nd statement is not a good statement as it is not accurate, it says nothing about the concentration. It is hard to say it is right or wrong, but not to be too precise, it should be a correct statement.