Can coal, petroleum and natural gas be prepared in the laboratory from dead organisms ?

Non-Stoichiometric cuprous oxide, Cu_2O can be prepared in laboratory. In this oxide, copper to oxygen ratio is slightly less than 2:1. Can you account for the fact that this substance is a p-type semiconductor?

How pure N_2 gas is prepared in laboratory? Write the necessary equation for the reaction.

Name two poisonous gases which can be prepared from chlorine gas.

Why can't we prepare a colloidal solution of a gas in gas type?

An object of size 7.0cm is placed at 27cm in front of a concave mirror of focal length 18cm. At what distance from the mirror should a screen be placed,so that a sharp focussed image can be obtained? Find the size and the nature of the image.