Question

state the role of nitric acid in assay of Ammonium Chloride​

Answer 1

state the role of nitric acid in assay of Ammonium Chloride

Answer 2

Nitric acid in Assay of Ammonium Chloride​

Explanation:

• Use the indirect test method to measure ammonium chloride. The sample is dissolved in water and treated with a formaldehyde solution that has been previously neutralised.
• (Methyleneimine is produced, which polymerizes into Hexamine.) Hydrochloric acid, corresponding to ammonium chloride, released quantitatively.
• By adding a dilute sodium hydroxide solution to a solution and gradually heating it, ammonium ions can be recognised. Ammonium ions will be transformed to ammonia gas if they are present.
• Ammonia has a peculiar smell that is suffocating. It also changes the colour of damp red litmus paper or damp universal indicator paper from red to blue.
• Nitric acid is concentrated and ammonia is used in anhydrous form (gas). Because of its highly exothermic nature, the reaction is quite violent.
• The freed HCl is titrated with a standard NaOH solution using phenolphthalein as an indicator, and the appearance of a pale pink colour indicates the endpoint.
• In an indirect calibration, the standard's value is expressed in a different quantity than the output, i.e., the measurement and the measurand are not the same.
• This is the most common kind of calibration in chemical analysis, for example, the calibration of a spectrophotometric method.