A powder of element X burns with a blue flame forming suffocate smelling gas which turns moist blue litmus to red and is a major air pollutant. X may be-

The powder of sulphur burns with the blue flame which produces suffocating smelling gas which is sulphur dioxide. As sulphur is a non-metal and oxides that are formed after its burning turns blue litmus to red. SO₂ is acidic in nature and it is one of the major air pollutants.