1.
a) Salt: any chemical compound formed from the reaction of an acid with a base, with all or part of the hydrogen of the acid replaced by a metal or other cation.
Acid + alkali → salt + water
b)
Tetraoxosulfate (VI), SO2−4,SO42−, is the second conjugate base from the dissociation of sulfuric acid, H2SO4.H2SO4. This acid is a diprotic acid and thus can donate two protons in an aqueous solution to form HSO−4HSO4− after the first dissociation and SO2−4SO42− after the second dissociation.
The fact that tetraoxosulfate (VI) is dibasic means in terms of Brønsted-Lowry acid-base theory, the ion can accept two protons, or in other words, the parent acid donates two protons upon dissociation. This can be shown by the equation of the reaction between the parent sulfuric acid and potassium hydroxide where two hydrogens are replaced:
H2SO4+2KOH → K2SO4+2H2O
2. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications. In nature, there are many systems that use buffering for pH regulation.
For example, blood in the human body is a buffer solution.
Buffer Solutions are used for fermentation in the making of alcohol
I've only answered 1 & 2
