Which of the following is the correct order of bond angles in the given hydrides?

Which of the following ions does not exist in an aqueous solution?

The important method for the fixation of nitrogen is

Phosphorus is manufactured by heating in an electric furnace a mixture of

Identify the $INCORRECT$ statement$(s)$ among the following:
$(I)$ Moist ammonia gas can be dried by using anhydrous $CaCl_2$
$(II)$ Phosphine is a weaker base than ammonia
$(III)$ $R_3SiCl$ produces very complex cross-linked polymeric silicone on hydrolysis
$(IV)$ When metallic copper reacts with $6 \ M$ $HNO_3$,$NO_2$ is the only product

Explain the molecular structure and properties of phosphorus trichloride $(PCl_{3})$.