a) The combustion of an organic compound in the presence of excess oxygen produced a gas , which makes clear lime water turbid. What element can be identified?

Question

b) A sample of this compound is treated with hot molten sodium metal, the obtained mixture is dissolved in water and is then filtered. To a portion of the obtained filtrate an iron ll nitrate solution is added, followed by adding an iron lll nitrate solution and a compound is formed which gives a blue color to the solution. 
Write the formula of the compound and give its name. 

Thank you.