Why do we add nitric acid?

Nitric acid is used in the production of ammonium nitrate and calcium ammonium nitrate which find applications as fertilizers. Ammonium nitrate is also used in the manufacturing of urea ammonium nitrate (UAN) used in fertilizer formulations and also as explosives.

How does nitric acid react with iron?

When iron is dipped in conc. HNO3, it becomes chemically inert or passive due to the formation of a layer of iron oxide (Fe3O4) on its surface. Concentrated nitric acid can be used to coat metals like iron, chromium, aluminium, and calcium, forming a protective oxide film that prevents further reactions.

Why is nitric acid used in halide test?

The nitric acid is added first to remove any carbonate ions that might be present – they would produce a white precipitate of silver carbonate, giving a false positive result for chloride ions.

Why should nitric acid be added before testing a solution for sulfate ions?

Barium nitrate solution can be used instead of barium chloride solution. However, nitric acid is added first to acidify the test solution. Sulfuric acid cannot be used because it contains sulfate ions – these would interfere with the second part of the test.

Why is iron rendered passive in nitric acid?

As a potent oxidising agent, Conc nitric acid transforms the metal into ferric oxide that forms an insoluble protective layer on it. Due to the formation of a reddish brown layer of iron oxide which prevents its further reaction with the acid, iron is made passive with fuming nitric acid.

Does iron dissolve in nitric acid?

Nitric acid dissolves most metals including iron, copper, and silver, with generally the liberation of lower oxides of nitrogen rather than hydrogen. It can also dissolve the noble metals with the addition of hydrochloric acid.

Where does nitric acid come from?

Nitric acid is made by the reaction of nitrogen dioxide (NO2) with water. Normally, the nitric oxide produced by the reaction is re-oxidized by the oxygen in air to produce additional nitrogen dioxide. Adding sulfuric acid to a nitrate salt and heating the mixture with an oil bath can make almost pure nitric acid.

How does the halide test work?

Halide ions in solutions are detected using silver nitrate solutions. The test solution is acidified using a few drops of dilute nitric acid, and then a few drops of silver nitrate solution are added. bromide ions give a cream precipitate of silver bromide. iodide ions give a yellow precipitate of silver iodide.

Why is nitric acid added to anion tests?

The nitric acid is added first to remove any carbonate ions that might be present – they would produce a white precipitate of silver carbonate, giving a false positive result for chloride ions.