Question

Carborundum is
(A) SiC
(B) $A{{l}_{2}}{{O}_{3}}.{{H}_{2}}O$
(C) $A{{l}_{2}}{{\left( S{{O}_{4}} \right)}_{3}}$
(D) $AlC{{l}_{3}}$

Answer 1

Looking at the options, we can analyse that all the given are nothing but ores. So basically, carborundum is the name of one of the following given options. Now if we know the names of ores, it becomes very easy to solve this question.

Complete step by step solution:
-Metal compounds found in nature are called minerals. Minerals from which we can extract metals conveniently as well as economically are called ores. It contains impurities which are called gangue. Ores are classified as
1. Native ores: They have metals in their free state like silver, gold.
2. Oxidized ores: They contain metal oxides like carbonates, phosphates,silicates,etc.
3. Sulphurised ores: They contain metal sulphides.
4. Halide ores: They contain metal halides.
-Extraction of metals from ores is called metallurgy. Carborundum is also an ore which is used to extract silicon. It is a semiconductor and is used in electronic devices as it is the basis of fabrication of electronic devices like diodes, MOSFETs, transistors, etc.
-Carborundum is also called silicon carbide and is denoted as SiC. It is a semiconductor that contains silicon and carbon. It occurs in nature only in the form of meteorites and so is prepared synthetically by the sintering process.
-Carborundum is coloured crystalline compound and its colour varies from yellow to green to bluish-black. It is insoluble in water but is soluble in molten alkalis and molten iron. It has a very good electron mobility due to which it is used in semiconductor devices. It has a refractive index of 2.55.
-As it does not exist naturally on earth, it is synthesized by combining silica sand which is found abundant in nature to carbon in an Acheson graphite electric resistance furnace. The temperature of the furnace is kept between 1600${}^\circ C$ to 2500${}^\circ C$. Silica fume is then heated with graphite to form SiC.
-SiC does not melt at any temperature known to us. It is also highly inert. This is also the reason why it is used in semiconductor devices. It has high electric field breakdown strength and also high current density. It has no phase transitions.
-SiC can form both p-type and n-type semiconductors by doping it with trivalent atoms like aluminium or boron and pentavalent atoms like arsenic and antimony. It also undergoes superconductivity.
-SiC is used in cutting tools, making plates of ballistic vests, automobile parts, crucibles, electric systems like lightning arresters and power lines, electronic elementary circuits, power electronic devices like FETs and diodes, making of LEDs and to make astronomical telescopes.

Thus option A is the correct one.

Note: Pure SiC is colourless. The bluish-black colour is obtained due to impurities present in the compound. These impurities are iron impurities. Lusters are present in the crystal which is formed by a passive layer of silicon dioxide which is formed on the surface due to reaction with atmospheric oxygen.