Tag: metallurgy
Questions Related to metallurgy
By annealing, steel :
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becomes soft
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becomes liquid
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become hard and brittle
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is covered with a thin film of $Fe _3O _4$
By annealing, steel becomes soft.
In anealing, steel is first heated to bright redness and then cooled slowly.
When $FeCr _2O _4$ is heated with carbon an alloy called ferrochrome is obtained.
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True
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False
Ferrochrome is produced by reduction of $Cr-ore$ (an oxide of Chromium and iron) with coal and coke.
In iron metallurgy, lime stone is used :
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To obtain heat energy
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To reduce iron oxide into iron
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As an iron ore
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To remove sand ($SiO _2$)
In the extraction of iron, the roasted ore is mixed with coke and lime stone (flux) and is then heated in the presence of air at high temperature in a furnace. Impurity of $SiO _2 $ is removed as calcium silicate $(CaSiO _3 slag)$.
$ CaCO _3\rightarrow CaO+CO _2$
$CaO+SiO _2\rightarrow CaSiO _3$
During smelting, an additional substance is added which combines with impurities to form a fusible product. It is known as :
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Slag
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Mud
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Gangue
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Flux
Flux is a substance which may be either acidic oxide $(Si{O} _{2})$ or basic oxide $(CaO, MgO)$. It combines with certain impurities (gangue particles) in order to form a substance called slag. This can be easily removed.
The pyrometallurgical operations involve the use of:
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High temperature
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Sulphide ores
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Electrolysis
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Complexation
Pyrometallurgy employs high temperatures to carry out smelting and refining operations to extract metals from their minerals.
Hydro-metallurgical process of extraction of metals is based on :
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Complex formation
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Hydrolysis
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Dehydration
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Dehydrogenation
Hydrometallurgy is a technique involving the use of aqueous chemistry for the recovery of metals from ores, concentrates, and recycled or residual materials. This process is used in extraction of less electro positive or less reactive metals like gold and silver by complex formation.
For the pyrometallurgical method used for the extraction of copper from sulphide ore, which statement(s) is/are correct?
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Pyrometallurgy is a dry method
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It involves concentration by leaching the sulphide ore with dil. $H _2SO _4$
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It involves concentration of the sulphide ore by froth flotation process
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It involves concentration by leaching for every ore
Smelting involves reduction of metal oxide with:
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Carbon
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Self reduction
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Magnesium
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Aluminium
Smelting is used to produce a base metal from its ore. The reducing agent is commonly a source of carbon such as coke, or in earlier times charcoal.
Copper can he extracted by hydrometallurgy but not zinc because:
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Copper is comparatively less active metal as its reduction potential is high. It can be displaced from solutions of $Cu^{2+}$ ion by more active metals.
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Zn displaced from solution of $Zn^{2+}$ ion, a more reactive metal than it, but then readily react with water forming their corresponding ions and evolve hydrogen gas.
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Both (A) and (B) are correct.
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Copper can never be extracted by hydrometallurgy.
Hydrometallurgy involves formation of aqueous complex compounds and is used in extraction of less electro positive or less reactive metals like gold and silver.
- Copper is also comparatively less active metal as its reduction potential is high and it can be displaced from solutions of $Cu^{2+}$ ion by more active metals.
- $Zn$ can also be displaced from solution of $Zn^{2+}$ ion by a more reactive metal than it, but then readily react with water forming their corresponding zinc ions and evolve hydrogen gas.
Metals which can be extracted by smelting process is/are:
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$Sn$
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$Cu$
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$Zn$
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$Al$
The process of extracting a metal from its oxide is known as 'smelting'. Most smelting processes involve direct reduction of the ore by carbon to metal and carbon dioxide. The production of primary aluminium is a good example of such a process.
Metals include copper, nickel, lead, zinc, silver, cobalt, gold, cadmium, etc.
Hence options A,B,C & D are correct.