Explain charcoal cavity test.

Charcoal cavity test.

• Take a small piece of charcoal block and make a fine hole (cavity) in the centre of it.
• Take a small amount of red mercury oxide and put it into the fine hole on the charcoal.
• The hole is known as a cavity and this test is known as a charcoal cavity.
• After some time red mercury oxide turns to a silver grey globule of metallic mercury.
• This indicates that mercury oxide is reduced to the metal mercury.
• $\mathrm{HgO}\left(\mathrm{s}\right)+\mathrm{C}\left(\mathrm{s}\right)\underset{}{\to \mathrm{Hg}\left(\mathrm{l}\right)+\mathrm{CO}\left(\mathrm{g}\right)}$
• Mercury oxide(red) + Charcoal $\underset{}{\to }$ Mercury (Silver grey) + Carbon monoxide.