Question

What kind of ion is contained in salts that produce an acidic solution?

Answer 1

see below

Explanation:

A salt dissolved in water can have a neutral, acidic or basic reaction, because of the ions by which it is formed.
What is happening is called hydrolysis.
If the salt is made from strong acid and a strong base (for example `NaCl, KNO_3, Li_2SO_4`) hydrolysis doesn't happen and the reaction is neutral.

If the salt is made from weak acid and a strong base (for example `Na_2CO_3, KNO_2, Li_2S`) it happens a basic hydrolysis.
If the salt is made from strong acid and a weak base (for example `NH_4Cl, AgNO_3, ZnSO_4`) it happens an acid hydrolysis.

If the salt is made from weak acid and a weak base (for example `MgCO_3, AgNO_2, (NH_4)2S`) it happens an acid or basic hydrolysis, depending on the strengthof the ions.