Question

Name a metallic nitrate that is not to be used for the preparation of nitric acid in the lab.

Answer 1

Hint :We know that the nitric acid can be obtained by the thermal decomposition of a metal nitrate salt. This is followed by presence of a strong acid acting as a dehydrating agent to produce residual product of nitric acid.

Complete Step By Step Answer:
Sodium nitrate refers to an alkali metal nitrate salt having a chemical formula $ NaN{{O}_{3}} $ . This chemical compound is also called Chile saltpetre because vast deposits of the same were previously extracted in Chile, and also to differentiate it from normal saltpetre potassium nitrate. Moreover, the mineral form of sodium nitrate is also termed as nitrate, nitratine or soda nitre.
In this extractive distillation process with dehydrating agent like concentrated sulphuric acid:
The reactants are heated by the hot furnace gases due to which vapour of nitric acid is produced. The nitric acid vapours get collected in stoneware receivers, after they are cooled/condensed through the water-cooled silica pipes. This is the distillation step. The residual of sodium bisulphate solution formed during the reaction is removed by an outlet at the bottom of iron retort.
The metallic nitrate used for preparation of nitric acid in the lab is sodium nitrate or potassium nitrate. In lab nitric acid is prepared by heating potassium nitrate $ \left( KN{{O}_{3}} \right) $ or sodium nitrate $ \left( NaN{{O}_{3}} \right) $ and concentrated sulphuric acid $ \left( {{H}_{2}}S{{O}_{4}} \right) $ in a glass retort. Reaction is:
 $ NaN{{O}_{3\left( s \right)}}+{{H}_{2}}S{{O}_{4\left( conc \right)}}\to NaHS{{O}_{4\left( aq \right)}}+HN{{O}_{3\left( l \right)}} $
Nitric acid is the most common and important oxoacid of nitrogen. Laboratory grade nitric acid contains $ 68\text{ }% $ of $ HN{{O}_{3}} $ by mass and has a specific gravity of $ 1.504. $ In gaseous state nitric acid is a planar molecule and on aqueous medium nitric acid behaves as a strong acid giving hydronium and nitrate ions. So in the lab nitric acid is prepared by metal nitrate of sodium or potassium.

Note :
Remember that nitric acid is a strong acid with highly nitrating, oxidizing, hydrolyzing and activating ability making it essential in chemical production and fertilizer industry. It has high solubility in water and efficiency to make some metals passive, making it commercially suitable.