Occurrence Questions in English

(B) The elements that are least reactive are found in their native or free state in nature.
Among the given options,$Au$ (Gold) is a noble metal with very low reactivity,hence it is found in its native state.
Therefore,the correct option is $(B)$.

(D) . Pyrolusite is the mineral form of manganese dioxide $(MnO_2)$. It is an oxide ore of manganese,not a carbonate,sulphur,or silicon ore.

(A) $Al$ (Aluminum) is the most abundant metal in the earth's crust,accounting for approximately $8.1\%$ by weight.

(B) Among the given options,only $Sulphur$ is found in its free state in nature,typically as $S_8$ molecules. Other elements like $Iodine$,$Phosphorus$,and $Magnesium$ are highly reactive and are primarily found in combined states as compounds.

(B) On April $20, 1902$,Marie and Pierre Curie successfully isolated radioactive radium salts from the mineral pitchblende in their laboratory in Paris.
In $1898$,the Curies discovered the existence of the elements radium and polonium during their research on pitchblende.

(B) The most abundant element in the Earth's crust is oxygen,which accounts for approximately $46.1 \%$ by weight.
It is followed by silicon $(28.2 \%)$ and aluminium $(8.23 \%)$.

(B) Naturally occurring substances from which a metal can be profitably (or economically) extracted are called $Ores$.

(D) $Bauxite$ is an ore of $Aluminum$.
$Dolomite$ is an ore of $Magnesium$.
$Chalcopyrites$ is an ore of $Copper$.
$Ilmenite$ $(FeTiO_3)$ is an ore of $Titanium$.
Therefore,the correct option is $D$.

(D) Pitchblende,also known as uraninite,is a radioactive,uranium-rich mineral ore with the chemical composition $UO_2$. It is the primary ore of uranium $(U)$. Additionally,it is historically significant as the source from which Marie Curie isolated radium $(Ra)$. Therefore,pitchblende is a source of both uranium and radium.

(C) An ore is a type of rock that contains sufficient minerals with important elements including metals that can be economically extracted from the rock.
$A$ mineral is called an ore when a metal can be profitably extracted from it.

(A) The correct statement is that Bauxite is an ore of aluminium.
The chemical formula for Bauxite is $Al_2O_3 \cdot 2H_2O$.
Magnetite is an ore of iron $(Fe_3O_4)$.
Haematite is an ore of iron $(Fe_2O_3)$.
Pyrites (Iron Pyrites) is an ore of iron $(FeS_2)$.

(D) Nitrates are highly soluble in water. Due to their high solubility,they are easily washed away by rain and do not accumulate in the earth's crust to form stable mineral deposits. Therefore,they are the least likely to be found in minerals compared to chlorides,sulphates,or sulphides.

(A) Cinnabar is the most common and is the chief ore of mercury.
Its chemical formula is $HgS$.

(B) Gypsum is $CaSO_4 \cdot 2H_2O$,which is a mineral of calcium.
Bauxite $(Al_2O_3 \cdot 2H_2O)$,Cryolite $(Na_3AlF_6)$,and Corundum $(Al_2O_3)$ are all minerals/ores of aluminum.

(D) Cryolite $(Na_3AlF_6)$ is an example of a halide ore.
Other options:
Galena $(PbS)$ and Cinnabar $(HgS)$ are sulfide ores.
Bauxite $(Al_2O_3 \cdot 2H_2O)$ is an oxide ore.

(D) Pig iron is the most impure form of iron and contains the highest proportion of carbon $(2.5 - 4\%)$. It is a manufactured product,not a naturally occurring mineral or ore.
Malachite is an ore of copper with the formula $Cu(OH)_2 \cdot CuCO_3$.
Zinc blende is an ore of zinc with the formula $ZnS$.
Bauxite is an ore of aluminium with the formula $Al_2O_3 \cdot 2H_2O$.

(B)
Chile saltpetre is the common name for sodium nitrate,which has the chemical formula $NaNO_3$.
Therefore,it is an ore of sodium.

(D) Although $Corundum$,$Kaolin$,$Cryolite$,and $Bauxite$ are all ores of $Aluminium$,$Bauxite$ is the primary ore used for the industrial extraction of $Aluminium$ in $India$. This is because $Bauxite$ is found in much greater abundance compared to $Corundum$ and $Kaolin$.

(D) Bauxite is the most important ore of aluminium.
It is a hydrated aluminium oxide mineral with the chemical formula $Al_2O_3 \cdot 2H_2O$.
It is primarily used for the extraction of aluminium metal through the Bayer process followed by the Hall-$H$éroult process.

(C) $Cryolite$ is a mineral with the chemical formula $Na_3AlF_6$.
Its chemical name is $Sodium \ hexafluoroaluminate(III)$.

(C) Bauxite is the principal ore of aluminium. Its chemical composition is generally represented as $Al_2O_3 \cdot xH_2O$,where $x$ typically ranges from $1$ to $3$. Among the given options,$Al_2O_3 \cdot 2H_2O$ (also known as diaspore or boehmite depending on structure) is the most commonly cited representative formula for bauxite in textbooks.

(A) Aluminium is the most abundant metal in the earth's crust. It does not occur in the free state as it is a reactive metal.
Ores of aluminium include $Bauxite$,$Cryolite$,and $Corundum$. $Bauxite$ $(Al_2O_3 \cdot 2H_2O)$ is the most important and main ore of aluminium.

(A) Bauxite is $Al_2O_3 \cdot 2H_2O$.
Corundum is $Al_2O_3$.
Diaspore is $Al_2O_3 \cdot H_2O$.
Anhydrite is $CaSO_4$,which is a mineral of calcium,not aluminium.

(D) The chemical formulas for the given minerals are:
$1$. Cryolite: $Na_{3}AlF_{6}$ (contains $Al$)
$2$. Mica: $K_{2}O \cdot 3Al_{2}O_{3} \cdot 6SiO_{2} \cdot 2H_{2}O$ (contains $Al$)
$3$. Feldspar: $KAlSi_{3}O_{8}$ (contains $Al$)
$4$. Fluorspar: $CaF_{2}$ (does not contain $Al$)
Therefore,Fluorspar is the correct answer.

(A) The important oxide ores of iron are Haematite $(Fe_2O_3)$ and Magnetite $(Fe_3O_4)$.
$A$ is the correct option because Haematite is an oxide ore of iron.
$B$ (Siderite) is $FeCO_3$ (carbonate ore).
$C$ (Pyrites) is $FeS_2$ (sulphide ore).
$D$ (Malachite) is $CuCO_3 \cdot Cu(OH)_2$ (copper ore).

(C) Cryolite $(Na_3AlF_6)$ is an ore of fluorine and aluminium.
Bauxite $(Al_2O_3 \cdot 2H_2O)$ is the primary ore of aluminium.
Haematite $(Fe_2O_3)$ is the most important ore used for the industrial manufacture of iron.
Chalcopyrite $(CuFeS_2)$ is an ore of copper.

(D) Magnetite is a naturally occurring iron oxide mineral with the chemical formula $Fe_3O_4$. It is one of the principal ores of iron.

(C) The chemical formulas for the given ores are as follows:
$1$. Haematite: $Fe_2O_3$ (Ore of iron)
$2$. Magnetite: $Fe_3O_4$ (Ore of iron)
$3$. Cassiterite: $SnO_2$ (Ore of tin)
$4$. Limonite: $Fe_2O_3 \cdot 3H_2O$ (Ore of iron)
Therefore,Cassiterite is the ore that does not represent an ore of iron.

(B) The chemical formula of the iron ore haematite is $Fe_2O_3$.

(B) The chemical formula of Azurite is $2CuCO_3 \cdot Cu(OH)_2$.
It is a basic copper carbonate mineral.
Therefore,Azurite is an ore of $Cu$ (Copper).
Thus,the correct option is $(B)$.

(D) is the correct answer. Malachite is a carbonate ore of copper with the chemical formula $Cu(OH)_2 \cdot CuCO_3$. It is a significant source for the extraction of copper.

(B) Malachite is a green-colored copper carbonate hydroxide mineral with the chemical formula $CuCO_3 \cdot Cu(OH)_2$.
It is a significant ore of copper.

(B) Argentite,also known as silver glance,has the chemical formula $Ag_2S$. It is a primary ore of silver.

(A) Argentite is an ore of silver with the chemical formula $Ag_2S$.
Stibnite is an ore of antimony with the chemical formula $Sb_2S_3$.
Haematite is an ore of iron with the chemical formula $Fe_2O_3$.
Bauxite is an ore of aluminium with the chemical formula $Al_2O_3 \cdot 2H_2O$.

(D) Calamine is a mineral consisting of zinc carbonate,$ZnCO_3$.
It is an important ore of zinc.

(A) Calamine is $ZnCO_3$,Cryolite is $Na_3AlF_6$,Gibbsite is $Al(OH)_3$,and Malachite is $CuCO_3 \cdot Cu(OH)_2$.
Out of the above ores,Calamine is the only ore of $Zinc$.

(C) Zinc blende is $ZnS$,not $ZnCl_2$.

(C) Siderite is $FeCO_3$,Haematite is $Fe_2O_3$,and Galena is $PbS$.
Among the given ores,only Galena $(PbS)$ is the primary ore of lead from which it is commercially extracted.

(C) The ores of lead are:
$1$. Galena $(PbS)$
$2$. Anglesite $(PbSO_4)$
$3$. Cerrusite $(PbCO_3)$
Calamine is an ore of zinc $(ZnCO_3)$.
Therefore,the correct option is $(C)$.

(C) Galena is the principal ore of lead.
Its chemical formula is $PbS$ (lead sulfide).

(A) Bauxite is $Al_2O_3 \cdot 2H_2O$.
Malachite is $CuCO_3 \cdot Cu(OH)_2$.
Zinc blende is $ZnS$.
Felspar is $KAlSi_3O_8$.
Among the given options,Bauxite is an oxide ore.
Hence,Option $A$ is the correct answer.

(D) Cryolite is $Na_{3}AlF_{6}$,which is a mineral ore of $Aluminium$.

(D) Cassiterite is an ore of $Sn$.
It is also called tinstone and has the molecular formula $SnO_2$.
It is a heavy,metallic,hard tin dioxide that serves as the major ore of tin.
It is colourless when pure,but appears brown or black when iron impurities are present.

(B) The incorrect statement is $B$.
Calamine is $ZnCO_3$ and siderite is $FeCO_3$,which are both carbonates.
Argentite is $Ag_2S$ (sulphide) and cuprite is $Cu_2O$ (oxide),so the statement that both are oxides is incorrect.
Zinc blende is $ZnS$ and pyrites (iron pyrites) is $FeS_2$,which are both sulphides.
Malachite is $Cu(OH)_2 \cdot CuCO_3$ and azurite is $2CuCO_3 \cdot Cu(OH)_2$,which are both ores of copper.

(A) The chemical formula for Horn silver is $AgCl$,which is a chloride ore of silver.
Zincite is $ZnO$ (oxide).
Bauxite is $AlO_x(OH)_{3-2x}$ (oxide/hydroxide).
Felspar is a silicate mineral.
Therefore,the correct option is $(A)$.

(A) Aluminium is the most abundant metal in the Earth's crust. However,it is extracted from bauxite $(AlO_x(OH)_{3-2x})$ because bauxite is the most abundant and economically viable ore of aluminium,making the extraction process commercially feasible.

(B) The correct option is $(B)$.
Cryolite is a mineral ore of aluminum with the chemical formula $Na_3AlF_6$ (sodium hexafluoroaluminate).

(A) An ore is a mineral from which a metal can be extracted conveniently and profitably. Since not all minerals contain a high enough concentration of metal to make extraction economically viable,all ores are minerals,but all minerals are not ores.

(C) Corundum is a crystalline form of aluminium oxide with the chemical formula $Al_2O_3$.
Therefore,it is an ore of $Al$ (Aluminium).

(D) Minerals are naturally occurring chemical substances in the earth's crust.
An ore is a mineral from which a metal can be extracted profitably and conveniently.
Therefore,all ores are minerals,but all minerals are not necessarily ores.