hemistry Form 4: Chapter 9 - Making of AlloyAn alloy is a mixture of two or more elements with a certain fixed composition in which metal is the major component.

The making of alloy is: To increase the strength and hardness of a pure metal. To prevent corrosion. To improve the appearance of a pure metal.

Pure Metal

Pure metal is made up of one type of atoms that are in same size. Therefore, when a force is applied, the layers of atoms can slide over one another. Thus, metals are ductile or can be stretched.

There are some empty spaces in between the pure metal atoms. When a metal is knocked or pressed, groups of atoms may slide and then settle into new positions. Thus, metals are malleable or can be shaped.

Alloy

Some of the spaces between the metal atoms are filled up by the foreign atoms which may be bigger or smaller than the original metal atoms.The presence of foreign atoms disrupts the orderly arrangement or the pure metal.The layers of metal atoms are prevented from sliding over one another easily. This makes alloys stronger and harder than pure metals.

Examples of alloy

AlloyComposition

Steel99 %iron+1 %carbon

Stainless steel74 %iron+18 % chromium+ 8 % nickel

Bronze90 %copper+10 %tin

Brass70 %copper+30 %zinc

Magnalium70 %aluminium+30 %magnesium

Duralumin95 %aluminium+4 %copper+1 %magnesium

Pewter97 %tin+3 %lead and antimony

Solder50 %tin+50 %lead

cupronickel25 %copper+75 %nickel

Chemistry Form 4: Chapter 9 - Haber Process1. The physical properties of ammonia are: Colourless and alkaline gas Strong pungent smell Highly soluble in water2. Ammonia usually produces white fumes of ammonium chloride when reacted with hydrogen chloride.3. The main uses of ammonia are: Manufacturing nitrogen fertilizers Manufacturing nitric acid through Ostwald process. To make explosives, dyes, household cleaners and nylon As a cooling agent.Making of AmmoniaAmmonia is manufactured by combining nitrogen and hydrogen in an important industrial process called the Haber process. The reaction is reversible and the production of ammonia is exothermic.

Nitrogen gas is obtained from the fractional distillation of liquid air. Hydrogen gas is obtained through the reaction between natural gas and steam. Nitrogen and hydrogen are mixed in the ratio of 1:3

Click on the diagram below to play!

How to separate ammoniaWhen the gases leave the reactor they are hot and at a very high pressure. Ammonia is easily liquefied under pressure as long as it isn't too hot, and so the temperature of the mixture is lowered enough for the ammonia to turn to a liquid. The nitrogen and hydrogen remain as gases even under these high pressures, and can be recycled.

An ammonia production plant. Photo courtesy of WMC Resources Ltd