Occurrence Questions in English

(C) The chemical formulas for the given ores are:
$Cuprite = Cu_2O$
$Chalcocite = Cu_2S$
$Chalcopyrite = CuFeS_2$
$Malachite = Cu(OH)_2 \cdot CuCO_3$
Among these,$Chalcopyrite$ $(CuFeS_2)$ is the ore that contains both $Iron$ $(Fe)$ and $Copper$ $(Cu)$.

(C) Magnetite $(Fe_3O_4)$,Siderite $(FeCO_3)$,Limonite $(Fe_2O_3 \cdot 3H_2O)$,and Haematite $(Fe_2O_3)$ are common ores of iron.
Smithsonite is an ore of zinc with the chemical formula $(ZnCO_3)$.
Therefore,Smithsonite is not a mineral of iron.

(C) Carnalite is an important ore of magnesium.
Its chemical formula is $KCl \cdot MgCl_2 \cdot 6H_2O$.

(B) Metals that are low in the reactivity series are found in their native state because they do not react easily with oxygen,moisture,or other atmospheric gases.
$Cu$ (Copper) is one such metal that is found in its native state as nuggets in the Earth's crust.
$Al$,$Fe$,and $Mg$ are more reactive and are typically found in the form of oxides,carbonates,or sulfides.

(C) The most abundant metal in the earth's crust is $Al$ (Aluminum),which constitutes approximately $8.1\%$ by weight of the earth's crust.
Therefore,the correct option is $(C)$.

(D) The primary ore used for the industrial extraction of copper is $Chalcopyrite$ $(CuFeS_2)$.
While $Cuprite$ $(Cu_2O)$ is also a copper mineral,$Chalcopyrite$ is the most abundant and commercially significant source of copper.

(A) The chemical formulas for the principal ores of silver are as follows:
$1$. Argentite: $Ag_2S$
$2$. Horn silver: $AgCl$
$3$. Pyrargyrite: $AgSbS_2$
Therefore,the correct sequence is $Ag_2S, AgCl$ and $AgSbS_2$.

(A) The most important ore of tin $(Sn)$ is Cassiterite,which is chemically $SnO_2$.
$A$: Cassiterite $(SnO_2)$
$B$: Cryolite $(Na_3AlF_6)$
$C$: Cerussite $(PbCO_3)$
Therefore,the correct option is $(A)$.

(B) The chemical formulas for the given ores are:
$1$. Pyrolusite: $MnO_2$ (Oxide ore)
$2$. Malachite: $CuCO_3 \cdot Cu(OH)_2$ (Carbonate ore)
$3$. Diaspore: $Al_2O_3 \cdot H_2O$ (Oxide/Hydroxide ore)
$4$. Cassiterite: $SnO_2$ (Oxide ore)
Therefore,Malachite is a carbonate ore.

(D) The primary ore used for the extraction of copper is copper pyrite,which is chemically represented as $CuFeS_2$ (also known as Chalcopyrite). Therefore,the correct option is $(D)$.

(C) The impurities,such as sand,rocky materials,or earthy substances,associated with minerals used in metallurgy are collectively called $Gangue$.

(C) Refractory metals are a class of metals that are extraordinarily resistant to heat and wear. The primary reason they are used in the construction of furnaces is that they possess very high melting points,which allows them to maintain their structural integrity at extreme temperatures.

(D) Alumina is the common name for aluminum oxide,which has the chemical formula $Al_2O_3$.

(D) The correct mineral-formula pairs are:
Galena: $PbS$
Cassiterite: $SnO_2$
Dolomite: $CaCO_3 \cdot MgCO_3$
Magnesite: $MgCO_3$
Therefore,the correct option is $(D)$.

(C) Malleability is the property of a metal to be beaten into thin sheets.
Among all metals,$Gold$ $(Au)$ is known to be the most malleable metal.
It can be beaten into extremely thin leaves,often used in decorative applications.

(D) The correct answer is $(D)$.
$Pt$ (Platinum) is a noble metal,which means it is chemically inert and does not react easily with oxygen,moisture,or other substances in the environment.
Therefore,it is found in nature in its native or free state.

(A) Calamine is a zinc ore consisting primarily of zinc carbonate,$ZnCO_3$. It is a common source of zinc metal.

(B) Iron pyrites $(FeS_2)$ is also known as "Fools gold" because of its metallic luster and pale brass-yellow hue,which resembles gold.

(B) Brass is an alloy of $Cu$ and $Zn$. It typically contains $60-80\%$ copper and $20-40\%$ zinc.

(C) Bronze is an alloy primarily consisting of copper $(Cu)$ and tin $(Sn)$.
Specifically,bronze contains approximately $75-90\% \ Cu$ and $10-25\% \ Sn$.

(A) Emery is a natural rock that is used as an abrasive. It is composed primarily of corundum $(Al_2O_3)$ mixed with other minerals such as magnetite,hematite,or spinel. Therefore,it is considered an impure form of corundum.

(D) . Malachite $(Cu(OH)_2 \cdot CuCO_3)$ is a basic copper carbonate.

(A) The term $Cu_2O$ represents cuprous oxide,where copper is in the $+1$ oxidation state.
Cuprite is $Cu_2O$,which is a cuprous ore.
Malachite is $Cu(OH)_2 \cdot CuCO_3$,which contains cupric $(Cu^{2+})$ ions.
Chalcopyrite is $CuFeS_2$,which contains cupric $(Cu^{2+})$ ions.
Azurite is $Cu(OH)_2 \cdot 2CuCO_3$,which contains cupric $(Cu^{2+})$ ions.

(A) Horn silver is the common name for the mineral form of silver chloride,which has the chemical formula $AgCl$.

(D) The chemical formulas of the given minerals are:
$1$. Corundum: $Al_2O_3$
$2$. Diaspore: $AlO(OH)$ or $Al_2O_3 \cdot H_2O$
$3$. Bauxite: $Al_2O_3 \cdot 2H_2O$
$4$. Cryolite: $Na_3AlF_6$
Among these,$Na_3AlF_6$ (Cryolite) is a fluoride mineral and does not contain oxygen.

(C) Brass is an alloy of $Cu$ and $Zn$.
Solder is an alloy of $Pb$ and $Sn$.
Bronze is an alloy of $Cu$ and $Sn$.
Tin stone is the ore $SnO_2$.
Therefore,brass does not contain tin.

(D) Chromite ore is represented as $FeCr_2O_4$ or $FeO \cdot Cr_2O_3$.
In this compound,iron exists as $Fe^{2+}$ and chromium exists as $Cr^{3+}$.
Therefore,the oxidation state of iron is $+2$ and the oxidation state of chromium is $+3$.

(A) The main ore of silver is Argentite,which has the chemical formula $Ag_2S$.

(B) Cryolite is a mineral composed of sodium,aluminum,and fluorine.
Its chemical formula is $Na_3AlF_6$ (sodium hexafluoroaluminate).
It is primarily used in the electrolytic extraction of aluminum from alumina $(Al_2O_3)$ to lower the melting point of the mixture and increase its electrical conductivity.

(C) The chemical formulas for the given iron ores are:
$1$. Limonite: $Fe_2O_3 \cdot 3H_2O$ (Oxide ore)
$2$. Siderite: $FeCO_3$ (Carbonate ore)
$3$. Pyrite: $FeS_2$ (Sulfide ore)
$4$. Magnetite: $Fe_3O_4$ (Oxide ore)
Therefore,$FeS_2$ (Iron Pyrite) is the sulfide ore of iron.

(B) The chemical formula of copper glance is $Cu_2S$.
Since it contains sulfur,it is classified as a sulphide ore.

(B) Let us analyze the given options:
$A$: Calamine $(ZnCO_3)$ and Siderite $(FeCO_3)$ are indeed carbonates.
$B$: Argentite is $Ag_2S$ (a sulphide ore),not an oxide. Cuprite is $Cu_2O$ (an oxide ore). Since Argentite is a sulphide,this statement is incorrect.
$C$: Zinc blende $(ZnS)$ and Pyrites $(FeS_2)$ are indeed sulphides.
$D$: Malachite $(CuCO_3 \cdot Cu(OH)_2)$ and Azurite $(2CuCO_3 \cdot Cu(OH)_2)$ are indeed copper ores.
Therefore,the incorrect statement is $B$.

(C) The Earth's crust contains various elements. Among metals,$Aluminum$ $(Al)$ is the most abundant,accounting for approximately $8.3\%$ by weight. Silicon is the second most abundant element overall,but it is a metalloid,not a metal. Therefore,the correct answer is $Aluminum$.

(D) Argentite is a sulfide ore of silver with the chemical formula $Ag_2S$.

(C) Litharge is the common name for lead$(II)$ oxide,which has the chemical formula $PbO$.
Therefore,it is an ore/mineral of lead $(Pb)$.

(D) The chemical formula for Galena is $PbS$ (sulfide ore).
The chemical formula for Bauxite is $AlO_x(OH)_{3-2x}$ (oxide ore).
The chemical formula for Cinnabar is $HgS$ (sulfide ore).
The chemical formula for Cryolite is $Na_3AlF_6$ (halide ore).
Therefore,$Na_3AlF_6$ is a halide ore.

(C) mineral is a naturally occurring substance in the earth's crust containing metals in combined states. An ore is a mineral from which a metal can be extracted economically and profitably. Therefore,the key distinction is the profitability of the extraction process.

(D) The correct pairings are:
$Pb$ is extracted from $PbS$ (Galena).
$Fe$ is extracted from $Fe_2O_3$ (Haematite).
$Al$ is extracted from $Al_2O_3 \cdot 2H_2O$ (Bauxite).
$Mn$ is extracted from $MnO_2$ (Pyrolusite),whereas $Rutile$ is an ore of $Ti$ $(TiO_2)$.
Therefore,the pair $Mn - \text{Rutile}$ is incorrect.

(A) The chemical formulas for the given ores are:
$(a)$ Magnesite: $MgCO_3$ (Carbonate ore)
$(b)$ Siderite: $FeCO_3$ (Carbonate ore)
$(c)$ Zincite: $ZnO$ (Oxide ore)
$(d)$ Argentite: $Ag_2S$ (Sulphide ore)
Therefore,the correct set of carbonate ores is $(a)$ and $(b)$.

(C) Carnallite is a hydrated potassium magnesium chloride mineral.
Its chemical formula is $KCl \cdot MgCl_2 \cdot 6H_2O$.

(B) Calamine is a mineral composed of zinc carbonate $(ZnCO_3)$.
It is a primary ore of zinc.
Therefore,the correct option is $B$.

(D) Pyrolusite is a common mineral ore of manganese.
Its chemical formula is $MnO_2$ (manganese dioxide).
Therefore,the correct option is $D$.

(D) Ruby silver is a common name for the mineral pyrargyrite. Its chemical composition is $Ag_3SbS_3$. Therefore,the correct formula is $Ag_3SbS_3$.

(A) Aluminum is the most abundant metal in the Earth's crust,but it is highly reactive and found in ores. Bauxite $(AlO_x(OH)_{3-2x})$ is the most important ore of aluminum. It is preferred for extraction because it is available in large quantities and the extraction process is economically viable and relatively straightforward compared to other minerals like clay or mica.

(C) The chemical formula for Chalcopyrite is $CuFeS_2$.
It contains both copper $(Cu)$ and iron $(Fe)$ as metal components.
Cuprite is $Cu_2O$,Chalcocite is $Cu_2S$,and Malachite is $CuCO_3 \cdot Cu(OH)_2$.
Therefore,the correct option is $C$.

(B) The ores are as follows:
$1.$ Galena: $PbS$
$2.$ Calamine: $ZnCO_3$
$3.$ Cerussite: $PbCO_3$
$4.$ Cinnabar: $HgS$
Therefore,Calamine $(ZnCO_3)$ is the ore of zinc.

(B) $FeS_2$ (Iron pyrite) is commonly referred to as $'$Fools gold$'$ because of its metallic luster and pale brass-yellow hue,which resembles gold to the untrained eye.

(A) Pyrolusite is the common name for the mineral manganese dioxide,which has the chemical formula $MnO_2$. Since it is an oxide of manganese,it is classified as an oxide ore.