Name the gas in each of the following :
(i) The gas evolved on reaction of Aluminium with boiling concentrated caustic alkali solution.
(ii) The gas produced when excess ammonia reacts with chlorine.
(iii) A gas which turns acidified potassium dichromate clear green.
(iv) The gas produced when copper reacts with concentrated nitrit acid.
(v) The gas produced on reaction of dilute sulphuric acid with a metallic sulphide.
