Lecture 7 – Ammonia & the Harber’s Process

Nitrogen and Ammonia:

Ammonia is an industrially important gas and is widely used to manufacture fertilizers. It is industrially manufactures using Hydrogen and Nitrogen by the Harber’s Process.

Harber’s Process:

Nitrogen, obtained from the fractional distillation of liquid air and Hydrogen from Cracking of crude oil are made to react together in volumes of 1 : 3, respectively, at 450°C and 300atm in presence of Iron as a catalyst to yield Ammonia.

This is a reversible reaction; therefore the conditions are strictly maintained to ensure the maximum yield of Ammonia. It is an exothermic reaction; giving out heat and prefers low temperatures. The rate of the reaction however, decreases at low temperatures, therefore the temperature of 450°C is preferred to ensure a fast and maximum yield of ammonia,

Lecture 6 – Preparation of Salts: Precipitation

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 5a	www.bbc.co.uk
Figure 5b	socratic.org

Precipitation:

Precipitation is the method used to prepare insoluble salts. In this method 2 soluble solutions are reacted together to yield an insoluble salt. The insoluble salt is obtained by using filtering the solution and washing the residue insoluble salt with water and drying it, or decanting as shown in Figure 5a and 5b, respectively.

Figure 5a:

Figure 5b:

Example: Barium sulphate is prepared using aqueous solutions of barium chloride and sodium sulphate.

Salts and their solubilities:

Table 5: Salt and their solubilities are shown in the Table below.

Soluble	Insoluble
All nitrates	None
All Chlorides except	Silver chloride; AgCl Lead chloride PbCl2 Mercury chloride HgCl2
All Sulphates except	Cacium sulphate; CaSO4 Barium sulphate; BaSO4 Lead sulpahte; PbSO4
Sodium carbonate; Na2CO3 Potassium carbonate; K2CO3 Calcium carbonate; CaCO3	All Carbonates except

 

Lecture 5 – Preparation of Salts: Titration

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 3	www.rsc.org

Preparation of Salts:

Salts can be prepared by the reaction between acids and metals, bases and carbonates. (as explained in the properties of Acids). The techniques used are as follows:

1. Titration
2. Precipitation

Titration:

In titration; an acid of a known or unknown concentration is added from a burette to a base of known or unknown concentration in a flask. The acid is added till the required colour change is obtained using an indicator. The change of the colour of the indicator marks the end of the neutralization reaction. This method is used to prepare soluble salts.

Figure 3:

Soluble salts prepared by this method are obtained from their solutions, by heating the solution to evaporate excess water from the solution and then crystallization the solution to form salt crystals. 

Mathematics of Titration:

The equation of titration is given by:

Let’s consider the following equation for explaining the equation of titration:

M = Concentration of acid/alkali in moles/dm³

V = Volume of acid/alkali used in cm³

n = number of moles used according to the balanced chemical equation

Example: here, n_acid = 1 but n_alkali = 2, because 1 mole of the acid requires 2 moles of the alkali.