why CO2 is not organic this might be very childish question but i am comfused because they say that organic molecules are those that contain H and C if that is so how can you call carbontetrachloride organic, even it hasn't any H atoms
Carbon dioxide 
"is" neither organic nor inorganic, it's just carbon dioxide. 
This distinction is nothing but a convention to separate things 
between the textbooks and professors. 
Carbon dioxide forms carbonic acid in water and the usual salts. 
This was/is reason to think of it as inorganic. 
On the other hand, urea, the diamide of carbonic acid was thought
to be organic when Wöhler synthesized urea for the first time 
in lab, today it is categorized as inorganic.