Question

What are ''fuming" acids'?

Answer 1

The most common fuming acids are fuming nitric acid and fuming sulfuric acid.

Explanation:

Fuming nitric acid

Red fuming nitric acid consists of `"84 %HNO"_3, "13% N"_2"O"_4`, and `"1–2 % H"_2"O"`.

The color is due to the `"N"_2"O"_4`, which breaks down partially to form nitrogen dioxide.

`underbrace("N"_2"O"_4)_color(red)("colourless") ⇌ underbrace(2"NO"_2)_color(red)("reddish-brown")`

When you open a bottle of fuming nitric acid, some of the dissolved `"NO"_2` escapes into the atmosphere as a reddish-brown gas with a suffocating odour.

Fuming sulfuric acid

Fuming sulfuric is made by dissolving `"SO"_3` in `"H"_2"SO"_4`.

When you open a bottle of fuming sulfuric acid, some of the dissolved `"SO"_3` escapes into the atmosphere.

The colourless gas reacts with moisture in the air, creating a white cloud of tiny sulfuric acid droplets.

`"SO"_3 +"H"_2"O" → "H"_2"SO"_4`

The white cloud is the "fume" in fuming sulfuric acid.