Oxides of N, P and As when dissolves in water to form oxy acids. Oxy acids of Sb and Bi are not stable.

Some important oxy acids:

Element Formula of the oxyacid Name of the oxyacid Oxidation state of element in oxyacid
Nitrogen H2N2O2 Hyponitrous acid +1
HNO2 Nitrous acid +3
HNO3 Nitric acid +5
Phosphorus H3PO2 Hypo phosphorus acid +1
H3PO3 Phosphorus acid +3
H3PO4 Phosphoric acid +5
(HPO4)n Metaphosphoric acid +5
H4P2O7 Pyrophosphoric acid +5
Arsenic H3AsO3 Arsenious acid +3
H3AsO4 Arsenic acid +5
Sb & Bi No stable acid

Oxyacids of Nitrogen , HNO3 , Nitric acid
Nitric acid is also known as aqua fortis (meaning strong water) which was given by alchemists.

Methods of preparation
(a) Laboratory preparation

KNO3 + H2SO4 → KHSO4 + HNO3

(b) Birkeland Eyde process

N2 + O2 ⇌ 2NO – 43,200 calories

The formation of nitric oxide is favoured by high temperature thus it is maintained at 3000°C.
The nitric oxide is cooled to 1000oC as to prevent its decomposition. Nitric oxide further combines with O2 .
2NO + O2 → 2NO2
The vapours then passed through water when nitric acid is produced.
2NO2 + H2O → HNO3 + HNO2
3HNO2 → HNO3 + 2NO + H2O

(c) Ostwald’s process (Modern process)
In this process the nitric acid is formed first when NH3 and air passed over platinum gauze at 750 – 900°C

The p Block Elements Chemistry Notes
The nitric oxide is then oxidised to NO2 by air which is cooled to 50°C and absorbed in water.
2NO + O2 → 2NO2
3NO2 + H2O → 2HNO3 + NO

Fuming nitric acid
When NO2 is dissolved in conc. nitric acid it forms fuming nitric acid. It is brown in colour. It is obtained by distilling concentrated HNO3 with a little starch.

Physical properties
HNO3 is colourless fuming with pungent smell soluble in water. Nitric acid usually acquires yellow
colour due to its decomposition by sunlight into NO2 .

The p Block Elements Chemistry Notes
Chemical properties

The p Block Elements Chemistry Notes

The p Block Elements Chemistry Notes

« Click Here for Previous Topic Click Here for Next Topic »

Class 12 Chemistry “The p Block Elements” All Topic Notes Class 12 Chemistry All Chapters Notes

You wish to report grammatical or factual errors within our online articles, you can let us know using the article feedback form.

comments