General Knowledge - General Science - Discussion

Hydrogen sulphide is answer it reacts with metal.

Safe corrosion will look reddish, black to brown or green to blue. Safe corrosion will occur if the brass has been kept clean and dry. If it is brownish or black this will be due to oxidization of the copper which occurs when exposed to air; this a natural phenomenon and is non-destructive. This is usually called "tarnish" and can be removed by careful cleaning and polishing. If the corrosion is green, continuous and non-flaky this again is safe corrosion.

First we have to remember what are the components of brass?

When copper are colour less they are oxidize.

I think it will not discolour. It may become black in colour, because of the presence of CU and Zn. If it react with H2S it forms CuS AND ZnS.

It is H2 sulfide because brass contain them since it is an alloy made of it and tin.

Oxygen is correct because it easily reacts with corban compounds due to that it changes its colour.

I think because other options are less reactive than H2s, and it reacts to give that colour.

Brass react with hydrogen sulphide results hot and cold condition so it becomes colourless.

Because brass is metal it get react with sulphide.