Ammonia is a widely used chemical having characteristic properties.
Properties of ammonia
- is a gas having a characteristic pungent smell
- is alkaline - turns wet red litmus paper blue
- lighter than air - can be collected via upward delivery
- highly soluble in water - turns water alkaline
Preparation of Ammonia
Ammonia preparation involves a reversible reaction starting from hydrogen and Nitrogen
3H2 (g) +2N2 (g) ⇌ 2NH3 (g)
for the industrial preparation of ammonia
- Nitrogen is obtained by fractional distillation of atmospheric air
- Hydrogen is obtained by cracking oil
Essential conditions for the manufacture of ammonia by the Haber process
The process of preparing ammonia is also referred as Haber process
Conditions used in haber process
- Temperature 450 °C
- Pressure 200 atm
- Iron fillings as the catalyst
Reasons for using the above conditions can be explained by their effect on obtaining higher yields of ammonia by the reversible reaction of preparing ammonia.
refer about reversible reactions
refer about reversible reactions
Temperature:
The forward reaction is an exothermic reaction for the preparation of ammonia. If the temperature was increased, it will favor the backward reaction. However lower temperatures , even favoring the forward reaction, does not provide enough activation energy for the reaction to take place. The yield of ammonia will be less due to lack of collisions between the reactant particles. Therefore the temperature used in haber process is said to be a moderate temperature.
Pressure:
High pressures always favor the reaction producing less number of moles in a reversible reaction. Therefore a high temperature as 200atm is used in haber process for a higher yield of ammonia.
Catalyst:
A catalyst favors both forward reaction and the backward reaction in a reversible reaction making the time taken to reach the equilibrium reducing the activation energy of the reaction. Iron fillings is used as the catalyst in the haber process.
Uses of ammonia
One of the main uses of ammonia in industry is producing nitrogenous fertilizers. Nitrogenous fertilizers contain soluble nitrogen salts promoting plant growth.
Effect of adding Calcium hydroxide to soil with added nitrogenous fertilizers
Soil pH is a very important factor considered in plant growth. Soil pH requirement is different from one crop to another. Less soil pH or high acidity in soil is a problem faced by maney farmers which can be treated by adding alkalies like Ca(OH)2
However when alkalies are added, it causes loss of nitrogen from the soil by the added nitrogenous fertilizers.
e.g:
2NH4NO3 (s) + Ca(OH)2 (aq)-> Ca(NO3)2 (aq) + 2NH3 (g) +2 H2O (l)
According to the reaction Ammonia gas is produced by the reaction. As Ammonia is a gas it will cause the loss of nitrogen from soil.
11:19 PM
ammonia
Calcium hydroxide
catalyst
Conditions
Haber process
hydrogen
loss of nitrogen from soil
Nitrogen
nitrogenous fertilizers
obtained
Preparation
Pressure
Properties of ammonia
Temperature
Uses
