Occurrence of metals - class-XII

Out of many minerals in which a metal may be found, only a few are viable to be used as source of that metal. Such minerals are known as ores.
Not all elements exists in pure states. Some elements exist in combined states.Among them the viable ones are there ores and the pure metal is obtained after undergoing various metallurgical processes.
Pyrolusite-($MnO _2$) is an oxide ore of Manganese.

The impurities of the furnace are acidic. So to remove them, basic fluxes are added to remove it as slag.

Aluminium is the first most abundant metal element and Iron is the next element.

Flux is added to remove impurities as slag. So impurities like Sulphur, Silicon and Phosphorous are removed from case Iron by adding flux. Here flux is $CaC{ O } _{ 3 }$

Metals below carbon in the reactivity series can be extracted using carbon. Carbon reduces the metal oxides that are extracted when heated. 

$MnO + SiO _2 \rightarrow MnSiO _3(Slag)$

Electrolytic reduction method is used for entraction of highly electropositive elements.

Cinnabar (HgS) is an ore of mercury, which is a low-reactivity metal. Heating cinnabar in air readily reduces it to liquid mercury without needing an extra reducing agent because thermal decomposition alone is sufficient.

Gold because of its inert nature does not combine with oxygen, hydrogen or humidity easily and thus occur in native state or free state.

(i) Mineral is a naturally occurring substance that is solid and inorganic represented by chemical formula and has ordered structure. Minerals are differentiated based on their physical and chemical properties.
(ii) Ore is a type of rock that contains sufficient minerals with metals which are economically extracted by mining. Metal ores are generally oxides,sulphides,silicates. The ores are processed to extract metals.
(iii) Gangue are the impurities which are mixed closely with the ores. It is unwanted material which is of no market value and it is waste rock or mineral or sand etc.

Impurities like sand,stones and rocky material present with ores are removed by employing various processes either physical or chemical in many steps and these are known as gangue.

To obtain a metal from its ore is called extraction of metal. The various process involved in the extraction of metals from the ores and refining are known as metallurgy.

Ores contain some impurities in the form of clay or rocky material known as gangue.

The process of extracting metals from their ores is called as metalurgy.The process employed in the extraction of the ore depends on the nature of the ore and the impurities present in it.The following are the basic steps for a metallurgical operation;

1. Crushing and grinding of the ore.
2. Concentration of the ore 
3. Working of the ore 
4. Purification or refining of the metal

Metallurgy is the science of extracting metals from their ores and modifying the metals for use. It is a commercial method.

The process containing the extraction or refining of metals is known as metallurgy.

During the extraction and processing of lithium, specifically from mineral sources like lepidolite or pollucite, rubidium and caesium are frequently obtained as valuable by-products due to their chemical similarities and concurrent occurrence.

Calcination is a process of heating to high temperature in air or oxygen, however calcination is also used to mean a thermal treatment process in the absence or limited supply of air or oxygen.

Silver and Gold occur in native state (free state). 

Reaction to form slag
$CaO+SiO _2\rightarrow CaSiO _3$ (slag)

Slag formed in extraction of metals are lighter and having low melting point than metal so they generally appear in upper layer of solutions.

Metallurgy involves concentration, roasting/calcination, reduction, and refining. Corrosion is a degradation process, not a step in metal extraction.

1. Argentite $Ag _2S$
2.  Galena $PbS$
3.  Chalcocite $Cu _2S$
4.  Copper pyrite (chalco pyrite)$ [CuFeS _2]$
5.  Cassiiterite $SnO _2$
6.  Dolomite  [$ Ca Mg (CO _3) _2$]
7.  Bauxite $Al(OH) _3$

∴ Sulphide containing ores are$ Ag, Cu, Pb.$

Option A is correct.

electrometallurgical method is used for the extraction of metals which are reactive in nature.

Calcination is used for carbonates and hydrated oxides to remove CO2 or water. ZnO and MgO are already oxides and do not require calcination.

During concentration of ores, lighter earthy particles are freed from the heavier particles using water. This is carried out by gravity separation or hydraulic washing or levigation.
During leaching, the soluble material is extracted from insoluble material by dissolving out in a suitable solvent.

$\underset {(P)}{SnCl _{2}} + Cl^{-} \rightarrow \underset {(X)}{SnCl _{3}^{-}}$
$\underset {(P)}{SnCl _{2}} + Me _{3}N \rightarrow \underset {(Y)}{SnCl _{2} [N(CH _{3}) _{3}]}$
$\underset {(P)}{SnCl _{2}} + 2CuCl _{2}\rightarrow \underset {(Z)}{SnCl _{4}} + CuCl$.

Flux is used to remove the gangue to form easily fusible slag.
$\underset {flux} {SiO _2} +\underset {gangue} {FeO}\rightarrow \underset {slag} {FeSiO _3}$

Ag and Pt are found in native (free) state.
Native silver usually occurs associated with coppr and gold, e.g., in alluvial sands.

In the process of smelting, inorganic chlorides, fluorides, limestone and other materials are designated as "fluxes" when added to the contents of a smelting furnace or a cupola for the purpose of purging the metal of chemical impurities such as phosphorus, and of rendering slag more liquid at the smelting temperature.

In the smelting process the black Sn is mixed with anthracite and little limestone which acts as flux, now this mixture is heated to a degree centigrade of 1200-1300, as a result, $SnO _2$ is reduced to Sn. This crude is having many acid impurities which can be removed as slag.$SnO _2+2C \Rightarrow Sn+2C$.

Azurite is one of the basic copper (II) carbonate minerals, the other being bright green malachite. Simple copper carbonate (CuCO3) is not known to exist in nature. Azurite has the formula $Cu(CO _3) _2(OH) _2$ with the copper (II) cations linked to two different anions, carbonate and hydroxide.

Hence the composition of azurite mineral is $2CuCO _3.Cu (OH) _2$

Sodium (alkali metal) is highly reactive and so, it occurs as a compound i.e. in combined form like NaCl.

${Ca _3(PO _4) _2}$ is called as Thomas slag and is used in cement manufacturing and manufacturing of phosphorus fertilizer,so options A,B & C are correct stetements.
Options A,B & C  are correct.

Aluminum is the most abundant metal in the earth's crust but it is never found free in nature. Silicon is not a metal.

Silicon is the most abundant element in the earth crust. It is found in rocks .

The impurities present in the ore is known as gangue. The removal of impurities from the ore is known as concentartion of ore.

In smelting, a flux is added to react with non-fusible gangue to form a fusible product called slag.

The process of extraction, purification and refining of metals from ore is called metallurgy.

RCC is Reinforced concrete cement. It is a combination of concrete and steel to build a structure instead of using only concrete. Concrete is good in resisting compression and to gain resisting tension steel is added which has high tensile strength. To overcome the drawback of concrete, reinforced steel bars are used along with concrete.

Aluminium is the most abundant element in the earth's crust. It is most abundant in terms of quantity.

A noble metal is any metal that is found in its metallic form, either pure or alloyed, in nature. Over geological time scales, very few metals can resist natural weathering processes like oxidation, which is why generally only the less reactive metals such as gold and platinum are found as noble metals.

Coke, limestone flux, and iron ore are charged into the top of the furnace in a precise filling order which helps control gas flow and the chemical reactions inside the furnace. Hence, The flux used in the extraction of iron is limestone. 

In blast furnace, products are collected at bottom. So, molten metal should be at bottom and slag is at up. So slag should have low density compared to molten metal.

Zinc Sulphide and Calamine responds for the process because, in $ZnS$, only zinc comes at smelting and after process, high purity comes after distillation. similar to Calamine, after distillation, the metal obtained is pure.

Gold is less reactive element. In electrochemical series, it is lower than Hydrogen. It doesn't react with anything. So it occurs as native metal.

The principle ore of copper is copper pyrite $(CuFeS _2)$ and copper is extracted from this ore. 

Haematite is iron(III) oxide (Fe2O3), which is an oxide ore. Malachite is a carbonate, Chalcopyrite is a sulfide, and Zinc blende is a sulfide.

Slag is the fusible compound formed by the combination of flux and gangue.

$\underset{Flux}{CaO}+\underset{Gangue}{SiO _2} \rightarrow \underset{Slag}{CaSiO _3}$

At the temperature of the slag zone in the metallurgy of iron using blast furnace is $800^oC – 1000^oC$.

Option (C) is correct.

Hand picking is effective in solid mixtures as the impurities, that we want to separate are visible to eye.

Gold and silver are extracted from their native ores by leaching. Leaching involves the treatment of the ore with suitable reagent as to make it soluble while impurities remain insoluble.

Iron, Nickel, Chromium

Roasting is a process of heating of sulphide ore to a high temperature in the presence of air. It is a step of the processing of certain ores.

Ore of copper is malachite $CuCO _{3}.Cu(OH) _{2}$.

The ore that can be concentrated by magnetic separation method is pyrolusite $(MnO _{2})$.
In this method, the ferromagnetic and non-magnetic particles in the ore are separated by an electromagnetic separator.

Solution:- (B) Roads

Solution:- 

Solution:- (B) bessemer converter

As dressing is the process which have extraction and dressing. So, unwanted materials are removed through this method.

Lime stone in the manufacture of Hematite ore is called flux. It removes unwanted material combining with gangue. 

Slag formed in extraction of iron is consists of $CaSiO _3$ which is further used for making cement.
Also, formation of this slag prevents the re-oxidation of molten iron.

Matte contains mainly ${Cu} _{2}S$ and $FeS$. It also contains coke and sand. It is the molten metal obtained from the blast furnace.

Chromium (Cr) metal is present in Ruby as an impurity. Ruby has pink to blood-red colour. It is a  gemstone. It is a variety of the mineral corundum (aluminium oxide).