Properties and uses of ammonia

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

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.

Hydrogen as a fuel

Presently Most widely used energy resource  is fossil fuels. However  fossil fuels are associated with many disadvantageous features such as

• non- renewable

Fossil fuels when once used it is again cannot be used and it takes billions of years to form it back from fossilized plants and animals. It is said the remaining fossil fuels will not be enough to fulfill the  increasing energy requirements in future.

• Causes environmental pollution

By burning fossil fuels number of pollutant gases are evolved. Namely Carbon dioxide which causes green house effect causing global warming and acid rain. Carbon monoxide which is a well known poisonous gas which causes breathing difficulties. Unburn hydrocarbons causing global warming.

• Expensive

Process of mining and refining of fossil fuels are very expensive processors and also it is a limited resource found only in few parts of the world. As a result prizes of fossil fuels are rising day by day.

To avoid these disadvantages caused by fossil fuels, scientists are trying to invent alternative fuel sources.

Hydrogen is one the main alternative and also Hydrogen is considered as the potential fuel for future.

Advantages of using Hydrogen as a fuel

• Hydrogen can produce lot of heat by burning

Compared to the fossil fuels by burning 1 g of Hydrogen produces more enregy

• Hydrogen is non- renewable

Main resource to produce hydrogen would be water. water is a  renewable source therefore hydrogen is also a renewable resource.

• Does not produce pollutants by burning

Only product produced by burning hydrogen is water which is not a environmental pollutant.

However the use of hydrogen is limited by some disadvantages .

Disadvantages of using Hydrogen

• Expensive

Production of Hydrogen by electrolysis of water is an expensive process.

• Difficulty of transport

Hydrogen being a gas is difficult to transport. It can be first reacted with metal halides and stored before the use.

• Explosiveness

Hydrogen is considered as an explosive gas because it produces lot of heat by burning and produce a sound. However under normal room temperatures hydrogen will not burn explosively

Identification of ions and gases

Different tests can be performed to test for different gases

1. Oxygen

Oxygen is a colorless odorless gas. As it is the gas helping to burn it can be tested by 

:entering a glowing splint in to the gas 

then the glowing splint will be relighted.

Method of preparation of Oxygen gas: add Manganese dioxide into hydrogen peroxide and collect via upward delivery

2. Chlorine

Chlorine is a toxic gas having a pale yellow color.As it has bleaching properties it can be tested by

: Keeping a damp red/blue litmus paper

then the litmus paper will become white( bleached)

Method of preparation of Chlorine gas: add HCl in to solid potassium permangenate

3. Hydrogen 

Hydrogen is a colorless odorless gas that can burn and can be used as a fuel. Test for Hydrogen is 

: enter a burning splint 

then it will burn with a characteristic 'pop' sound

Method of preparation of Hydrogen: add HCl in to zinc

4. Ammonia  

Ammonia is a gas having a characteristic odor but no color. As it forms alkaline ammonium hydroxide by dissolving in water it can be tested by

: keeping a damp red litmus paper

then it will turn blue

Method of preparation for ammonia: add sodium hydroxide to ammonium chloride