Question

What happens if you add `"H"_2"SO"_4` into water? What about if you combine `"H"_2"SO"_4` and `"HNO"_3`?

Answer 1

The mixture heats up as the sulfuric acid protonates the water and the nitric acid.

Explanation:

(a) `"H"_2"SO"_4` + water

Concentrated `"H"_2"SO"_4` is about 98 % `"H"_2"SO"_4` and 2 % water,

Concentrated `"HNO"_3` is about 70 % `"HNO"_3` and 30 % water.

You probably already know that the reaction of #"H"_2"SO"_4 with water is highly exothermic.

The same thing happens with the water in nitric acid.

`"H"_2"SO"_4 + "H"_2"O" → "H"_3"O"^"+"+ " HSO"_4^"-" + "heat"`

(b) `"H"_2"SO"_4` + nitric acid

Sulfuric acid is a stronger acid nitric acid.

It protonates the nitric acid in an acid-base reaction.

`underbrace("H"_2"SO"_4)_color(red)("acid") + underbrace("HO-NO"_2)_color(red)("base") → " HSO"_4^"-" +"H"_2stackrel(+)("O")"-NO"_2"`

You don't see anything happening, but this what takes place in the mixture.