What are ''fuming" acids'?

1 Answer
Feb 12, 2016

Answer:

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.