Question

Platinum is used as a catalyst in:
A. Oxidation of ammonia to form nitric acid
B. Hydrogenation of oils
C. Production of synthetic rubber
D. Synthesis of methanol

Answer 1

Hint: The formation of nitric acid from ammonia takes place through the oxidation process in which the oxygen atom reacts with ammonia. This process is known as Ostwald's process and an expensive metal is used as a catalyst.

Complete Solution :
 -Oxidation is the process in which the oxygen atom is added and the removal of hydrogen atom takes place.
-As we know that the molecular formula of ammonia is \[\text{N}{{\text{H}}_{3}}\]. So, it is oxidised to $\text{HN}{{\text{O}}_{3}}$ in two steps i.e. Catalytic oxidation reaction and absorption of nitrogen dioxide.
-Firstly, the primary oxidation takes place in which the chamber is filled with a 1:8 ratio of ammonia and oxygen with some catalyst such as platinum gauze or copper and nickel at a temperature of \[600{}^\circ \text{C}\].
-In the chamber the ammonia oxidises and forms nitric oxide:
$4N{{H}_{3}}+5{{O}_{2}}\xrightarrow{Pt}4NO+6{{H}_{2}}O$

-Now, secondary oxidation takes place in which the temperature of the nitric oxide is lowered.
-After the cooling process, it is transferred to another chamber in which nitric oxide is again oxidised to form nitrogen dioxide i.e.
$2NO+{{O}_{2}}\to 2N{{O}_{2}}$

Step 2 is the absorption of nitrogen dioxide
-In this process, the nitrogen dioxide absorbs water in the chamber and form nitric acid i.e.
$2N{{O}_{2}}+{{H}_{2}}O\to 2HN{{O}_{3}}+NO$

-The whole process was given by Wilhelm Ostwald and named the process Ostwald's process.
So, the correct answer is “Option A”.

Note: The reaction of the conversion of the ammonia to the nitric acid is the exothermic process because energy was released by the reaction. Moreover, sometimes this process can be dangerous due to the unfavourable condition such as the corrosiveness of nitric acid. So, one should take safety measures during the experiment.