Class x chemistry

Study of compound Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula NH₃. A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a characteristic pungent smell.

Formula: NH3 IUPAC ID: Azane Molar mass: 17.031 g/mol Boiling point: -33.34 °C Density: 0.73 kg/m³

Ammonia gas is usually prepared in the laboratory by gently heating ammonium chloride (NH4Cl) and slaked lime [Ca(OH)2].

NH3 is prepared in the laboratory by heating an ammonium salt with + NaOH. This is a standard test in the laboratory for NH4 compounds.

NH4Cl + Ca (OH)2 ------NH3 +CaCl2 +H2O

Industrial method –

What is Haber Process? Haber–Bosch process or just Haber process is basically one of the most efficient and successful industrial procedures to be adopted for the production of ammonia. German chemists Fritz Haber along with his assistant in the 20th century developed high-pressure devices and catalysts to carry out the process on a laboratory scale. Later, Carl Bosch in the year 1910 took the design and created a machine for industrial-level production. This was indeed an important development in the field of science. Let us look and understand the process below.

Explaining the Process and Conditions The Haber process provides a good case study to illustrate how industrial chemists use their knowledge of the factors that affect chemical equilibria to find the best conditions needed to produce a good yield of products at a reasonable rate.

In the Haber process, “the atmospheric nitrogen (N2) is converted to ammonia (NH3) by reacting it with hydrogen (H2)”. Here a metal catalyst is used and high temperatures and pressures are maintained. The raw materials for the process are

 Air, which supplies the nitrogen.  Natural gas and water which supply the hydrogen and the energy needed to heat the reactants.  Iron which is the catalyst and does not get used up. Let us take a look at the diagram below.

Haber Process – Manufacturing of Ammonia

1. As per the diagram, in the Haber process, we take nitrogen gas from the air and combine it with hydrogen atom obtained from natural gas in the ratio 1:3 by volume. 2. The gases are passed through four beds of catalyst, with cooling takes place in each pass. This is done to maintain equilibrium constant. 3. While different levels of conversion occur in each pass where unreacted gases are recycled. 4. Normally an iron catalyst is used in the process, and the whole procedure is conducted by maintaining a temperature of around 400 – 450oC and a pressure of 150 – 200 atm. 5. The process also involves steps like shift conversion, carbon dioxide removal, steam reforming, and methanation. 6. In the final stage of the process, the ammonia gas is cooled down to form a liquid solution which is then collected and stored in storage containers.

Reaction Rate and Equilibrium The Haber process for the synthesis of ammonia is based on the reaction of nitrogen and hydrogen. The chemical reaction is given below. Notably, in this process, the reaction is an exothermic reaction one where there is a release of energy.

N2(g) + 3H2(g) → 2NH3(g) Nitrogen in the reaction is obtained by separating nitrogen from the air through liquefaction and hydrogen is obtained from natural gas by steam reforming.

CH4(g) + H2O → H2(g) + CO(g) According to Le Chatteleir principle, the production of ammonia is favoured by high pressure and low temperature. The Haber process is typically carried out at pressures between 200 and 400 atmospheres and temperature of 500oC. In the commercial production of ammonia, NH3 is continuously removed as it is produced. Removing the products causes more nitrogen and hydrogen to combine according to Le Chatelier’s principle. The reaction is a reversible reaction. However, the reaction is affected by changes in temperature, pressure and catalyst used mainly in the composition of the equilibrium mixture, the rate of the reaction and the economics of the whole process

FAQs 1. How is ammonia manufactured by Haber’s process? Ans: Production of ammonia by the cycle of Haber. It is widely provided by the nitrogen (N2) and hydrogen (H2) Haber cycle. The Haber process takes nitrogen gas from the atmosphere and combines it to form ammonia gas with molecular hydrogen gas. 2. Why is iron catalyst used for Haber process? Ans: Iron is used in the Haber cycle as a cheap catalyst. It allows in acceptable time to reach a reasonable yield. State three conditions of reaction regulated in industrial reactions. 3. How do we get hydrogen for Haber process? Ans: Methane from natural gas is the main source of hydrogen. In a high-temperature and - pressure pipe inside a reformer with a nickel catalyst, the process, steam reforming, is carried out separating the carbon and hydrogen atoms in the natural gas. 4. What factors affect the Haber process? Ans: The yield of ammonia can be changed by increasing the pressure or temperature of the reaction because the Haber cycle is a reversible reaction. Increasing the reaction pressure increases ammonia yield

Physical properties---Ammonia is a colourless gas with a characteristically pungent smell. It is lighter than air, its density being 0.589 times that of air. It is easily liquefied due to the strong hydrogen bonding between molecules; the liquid boils at −33.3 °C (−27.94 °F), and freezes to white crystals at −77.7 °C (−107.86 °F).