Chemistry
State the colour of :
(i) pure nitric acid
(ii) nitric acid obtained in the laboratory
(iii) nitric acid obtained in the laboratory after passage of air or addition of water to it.
Nitric Acid
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Answer
(i) Colourless
(ii) Slightly yellowish brown due to decomposition of the acid which is negligible at ordinary temperature but substantial at high temperature
(iii) Colourless — bubbling of air drives out the reddish brown nitrogen dioxide gas from the warm acid and further oxidises nitrogen dioxide to nitric acid. Addition of water causes dissolution of the nitrogen dioxide gas which is soluble in water.
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In the laboratory preparation of nitric acid from – KNO3 or NaNO3 state :
(i) the acid used
(ii) the type of apparatus used
(iii) the precautions to be taken during the preparation
(iv) the method of collection of the acid
(v) the method of identification of the product i.e., acid formed.
Give reasons for the following — pertaining to the above laboratory preparation of nitric acid
(i) concentrated hydrochloric acid is not used as a reactant in the laboratory preparation.
(ii) the complete apparatus in the laboratory preparation does not contain parts made of rubber or cork.
(iii) the reaction temperature is maintained below 200°C
(iv) at high temperatures the sodium sulphate or potassium sulphate formed, forms a crust and sticks to the glass apparatus.
State which reaction of ammonia forms the first step of Ostwald's process.
Convert ammonia to nitric acid by Ostwald's process giving all conditions.