Which of the following is a true acidic anhydride?

$N_2$ combines with metals to form:

Which one of the following is not correct?

Ammonia can be dried by

Which of the following is one of the products obtained when calcined phosphate rock is reduced with coke and sand in an electric furnace at $1773 \ K$?

In the Haber process,hydrogen is obtained by reacting methane with steam in the presence of a $NiO$ catalyst. This process is known as steam reforming. Why is it necessary to remove $CO$ when ammonia is obtained by the Haber process?