When crystals of lead nitrate are heated strongly in a dry test tube :

When we heat lead nitrate [P(NO₃)₂] in a boiling tube, we observe the emission of brown fumes. Which one of the following is the brown gas?

Lead nitrate on heating gives

Copper sulphate crystals available in the market are blue coloured crystals. By careful heating, they turn to white colour. Which one of the following is responsible for the blue colour ?

When air is blown from mouth into a test tube containing limewater, the limewater turns milky. This is due to the presence of

Which one of the following materials is present in a guard tube (drying tube) that is used for preparation of HCl gas?