Which of the following reactions best represents lab scale preparation of nitric acid?

In the contact process, SO2 is passed twice through the catalytic converted. Why?

What is the maximum covalency of the nitrogen atom?

Which allotrope of phosphorus is the most reactive?

Who first recognized sulfur as an element?

Which of the following does not exist as an octatomic solid?

What is formed when amphoteric oxides react with an alkali solution?

Why is nitrogen preferably used in welding process and cooling of substances?