Occurrence Questions in English

(C) The chief ore of aluminium is bauxite $(Al_2O_3 \cdot 2H_2O)$.
Corundum $(Al_2O_3)$ and cryolite $(Na_3AlF_6)$ are also ores of aluminium.
Epsomite is a hydrous magnesium sulfate mineral with the formula $MgSO_4 \cdot 7H_2O$,which is an ore of magnesium,not aluminium.

(B) Haematite is $Fe_2O_3$,magnetite is $Fe_3O_4$,and Limonite is $FeO(OH) \cdot nH_2O$,while Magnesite is $MgCO_3$.
$\therefore$ Magnesite does not contain iron.

(C) Noble metals are expected to occur in the native state because of their low reactivity with other elements. These metals,such as $Au$,$Ag$,and $Pt$,do not easily react with oxygen,moisture,or other chemicals in the environment.

(D) Oxygen is the most abundant element in the earth's crust,accounting for approximately $46.6\%$ by weight.

(D) The most abundant metal in the earth's crust is Aluminium $(Al)$,followed by Iron $(Fe)$.
Therefore,the two most abundant metals are $Fe$ and $Al$.

(A) The naturally occurring chemical substances in the earth's crust are minerals. Ores are minerals from which metals can be extracted conveniently and profitably. Ores are usually associated with earthy or undesired materials such as sand,stones,etc.,which are collectively known as $Gangue$.

(C) Aluminium is the most abundant metal in the Earth's crust. It is primarily found in the form of oxide ores,such as bauxite $(Al_2O_3 \cdot 2H_2O)$.
Silver is typically found as sulfide or chloride ores.
Lead is mainly found as galena $(PbS)$.
Copper is found as sulfide ores like copper pyrites $(CuFeS_2)$ or oxide ores,but it is not its primary occurrence compared to aluminium.

(A) The three most abundant elements in the Earth's crust by mass are oxygen $(O)$,silicon $(Si)$,and aluminum $(Al)$.
Oxygen constitutes approximately $46.6\%$,silicon $27.7\%$,and aluminum $8.1\%$ of the Earth's crust.

(A) $Al$ is the most abundant metal in the earth's crust.
Aluminum is the third most abundant element $(7.4\,\%)$ of the earth's crust.
Oxygen and silicon are the first and second most abundant elements,but they are non-metals and metalloids,respectively.

(D) Stainless steel is an alloy primarily composed of iron,chromium,and carbon.
Chromium is the essential alloying element that provides corrosion resistance by forming a thin,passive layer of chromium oxide on the surface of the steel.
Therefore,among the given options,$Cr$ is the correct component.

(B) The reaction $SnCl_2 + HgCl_2 \to SnCl_4 + Hg$ indicates that $X$ is $Sn$ and $Y$ is $Hg$.
Thermal decomposition of $HgO$ occurs as: $HgO \xrightarrow[> 400^oC]{\Delta} Hg + \frac{1}{2} O_2$.
The primary ore of mercury $(Hg)$ is $HgS$,which is known as Cinnabar.

(D) Calamine is $ZnCO_3$ and Cerrusite is $PbCO_3$,both are carbonate ores.
Rutile is $TiO_2$ and Cuprite is $Cu_2O$,both are oxide ores.
Zinc blende is $ZnS$ and Pyrites (like Iron pyrites $FeS_2$ or Copper pyrites $CuFeS_2$) are sulphide ores.
Malachite $(CuCO_3 \cdot Cu(OH)_2)$ and Azurite $(2CuCO_3 \cdot Cu(OH)_2)$ are carbonate ores of $Cu$,not sulphate ores.
Therefore,the statement in option $D$ is incorrect.

(B) The correct chemical compositions of the given ores are as follows:
$1$. Sylvine: $KCl$ (Potassium ore)
$2$. Malachite: $Cu(OH)_2 \cdot CuCO_3$ (Copper ore)
$3$. Cinnabar: $HgS$ (Mercury ore)
$4$. Fluorite (Fluorspar): $CaF_2$ (Calcium ore)
Comparing these with the given options,the pair $B$ (Malachite $-$ Magnesium) is incorrectly matched,as Malachite is an ore of Copper,not Magnesium.

(B) The metal used for making joints in jewellery is copper $(Cu)$.

(C) Cuprite is an oxide mineral composed of copper$(I)$ oxide,$Cu_2O$.
Chalcocite,copper$(I)$ sulfide,$Cu_2S$,is an important copper ore mineral.
Chalcopyrite has the chemical formula $CuFeS_2$.
Malachite is a copper carbonate hydroxide mineral with the formula $Cu_2CO_3(OH)_2$.
Therefore,Chalcopyrite ore contains both copper and iron.

(A) The chemical formula of Chloroapatite is $Ca_5(PO_4)_3Cl$. It is a phosphate mineral,not a sulphur mineral.
Fool's gold is $FeS_2$,Sphalerite is $ZnS$,and Chalcopyrite is $CuFeS_2$,all of which are minerals of sulphur.

(C) Cinnabar is the common name for the mineral mercury$(II)$ sulfide,which has the chemical formula $HgS$. It is the primary ore of mercury $(Hg)$.

(D) The chemical formulas for the given ores are:
$1$. Cryolite: $Na_3AlF_6$ (a fluoride halide ore).
$2$. Fluorspar: $CaF_2$ (a fluoride halide ore).
$3$. Horn silver: $AgCl$ (a chloride halide ore).
$4$. Limonite: $Fe_2O_3 \cdot 3H_2O$ (an oxide ore).
Therefore,Limonite is not a halide ore.

(B) Argentite is a primary ore of silver with the chemical formula $Ag_2S$. It is commonly referred to as $Silver \ glance$ due to its metallic luster and appearance.

(D) Cassiterite is the primary ore of tin. Its chemical formula is $SnO_2$,which is tin$(IV)$ oxide. Therefore,the main constituent of cassiterite is oxide of tin.

(D) $1$. $Brass$ is an alloy of $Copper$ $(Cu)$ and $Zinc$ $(Zn)$.
$2$. $Bronze$ is an alloy of $Copper$ $(Cu)$ and $Tin$ $(Sn)$.
$3$. $Azurite$ is a copper mineral with the formula $Cu_3(CO_3)_2(OH)_2$.
$4$. $Calamine$ is a zinc mineral,primarily $Zinc$ $carbonate$ $(ZnCO_3)$.
Therefore,$Calamine$ does not contain $Copper$.

(D) Metals that are very low in the reactivity series are found in the free or native state because they are highly resistant to oxidation by atmospheric oxygen or moisture.
$Ag$ (Silver),$Au$ (Gold),and $Pt$ (Platinum) are noble metals and are found in the free state in nature.
Therefore,the correct option is $D$.

(A) mineral is a naturally occurring chemical substance in the earth's crust.
An ore is a mineral from which a metal can be extracted profitably and conveniently.
Therefore,the substance from which an element can be economically extracted is called an ore.

(B) The ores of magnesium include $MgCO_3$ (Magnesite),$MgSO_4 \cdot H_2O$ (Kieserite),and $MgCl_2 \cdot KCl \cdot 6H_2O$ (Carnallite).
Malachite is an ore of copper $(CuCO_3 \cdot Cu(OH)_2)$.
Magnetite is an ore of iron $(Fe_3O_4)$.
Calamine is an ore of zinc $(ZnCO_3)$.
Therefore,Kieserite is the correct ore of magnesium.

(B) $1$. Calamine is $ZnCO_3$ and siderite is $FeCO_3$. Both are carbonate ores. (Correct)
$2$. Argentite is $Ag_2S$ (sulphide) and cuprite is $Cu_2O$ (oxide). Since argentite is a sulphide ore,the statement that both are oxide ores is incorrect. (Incorrect)
$3$. Zinc blende is $ZnS$ and iron pyrites is $FeS_2$. Both are sulphide ores. (Correct)
$4$. Malachite is $Cu(OH)_2 \cdot CuCO_3$ and azurite is $Cu(OH)_2 \cdot 2CuCO_3$. Both are copper ores. (Correct)
Therefore,the incorrect statement is $B$.

(D) Let us analyze the composition of the given minerals:
$1$. Asbestos $(Mg_3Si_2O_5(OH)_4)$ and willemite $(Zn_2SiO_4)$ are indeed silicate minerals.
$2$. Anglesite $(PbSO_4)$ and barite $(BaSO_4)$ are sulfate minerals.
$3$. Sylvine $(KCl)$ and fluorspar $(CaF_2)$ are halide minerals.
$4$. Calamine $(ZnCO_3)$ and cerussite $(PbCO_3)$ are carbonate minerals of zinc and lead,respectively,not calcium. Therefore,statement $D$ is incorrect.

(D) Cassiterite,also known as tin stone,is the primary ore of tin $(Sn)$.
Its chemical formula is $SnO_2$.

(A) Galena is the chemical compound lead$(II)$ sulfide $(PbS)$.
It is the primary ore of lead $(Pb)$.

(B) The most important and commercially viable ore of iron is $Fe_2O_3$,which is known as Hematite.
It is widely used for the extraction of iron in blast furnaces due to its high iron content and ease of processing.

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

(B) Sphalerite,also known as zinc blende $(ZnS)$,is the primary ore of zinc.
It frequently contains cadmium $(Cd)$ as an impurity,which is recovered as a byproduct during the extraction of zinc.

(B) Ferrosoferric oxide is $Fe_3O_4$,which is a mixed oxide of $FeO$ and $Fe_2O_3$.
It is commonly known as Magnetite.

(B) Cuprite $(Cu_2O)$ is an oxide,while argentite $(Ag_2S)$ is a sulphide. Therefore,the statement that both are oxides is incorrect.
Calamine $(ZnCO_3)$ and siderite $(FeCO_3)$ are indeed carbonates.
Zinc blende $(ZnS)$ and pyrites $(FeS_2)$ are indeed sulphides.
Malachite $(CuCO_3 \cdot Cu(OH)_2)$ and azurite $(Cu_3(CO_3)_2(OH)_2)$ are indeed ores of copper.

(D) The chemical formulas for 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,Cryolite $(Na_3AlF_6)$ is a fluoroaluminate mineral and does not contain oxygen atoms.

(C) $1$. Solder is an alloy of lead $(Pb)$ and tin $(Sn)$.
$2$. Bronze is an alloy of copper $(Cu)$ and tin $(Sn)$.
$3$. Brass is an alloy of copper $(Cu)$ and zinc $(Zn)$. It does not contain tin $(Sn)$.
$4$. Tin stone is the ore of tin,which is tin dioxide $(SnO_2)$.
Therefore,brass does not contain tin.

(A) Silver,copper,and lead are commonly found in the Earth's crust as sulfide ores:
$Ag_2S$ (silver glance),
$CuFeS_2$ (copper pyrites),and
$PbS$ (galena).

(C) Pure iron is soft and stretches easily when hot. It is not suitable for making tools and machines because it lacks the necessary hardness and strength.
To make it useful,iron is mixed with small amounts of carbon to form steel,which is much harder and more durable.
Therefore,the Assertion is correct,but the Reason is incorrect because pure iron is soft,not hard.

(D) Iron is a moderately reactive metal and is not found in a free state in nature; it is typically found in the form of oxides,carbonates,or sulfides.
Therefore,the Assertion is incorrect,and the Reason is correct.

(D) Malachite is a green copper carbonate hydroxide mineral with the chemical formula $CuCO_3 \cdot Cu(OH)_2$.

(D) The correct definition of $Gangue$ is the earthy or undesired materials (such as sand,clay,or rocks) associated with the ore. Option $D$ is incorrect because $Gangue$ is not the ore itself,but the impurities present in the ore.

(N/A) Minerals are naturally occurring chemical substances found in the Earth's crust,which contain metals in various forms.
Ores are specific minerals from which a metal can be extracted conveniently and economically.
For example,while there are many minerals containing zinc,only specific ones like zinc blende $(ZnS)$,calamine $(ZnCO_3)$,and zincite $(ZnO)$ are considered ores because the extraction of zinc from these is profitable.

(N/A) Radiocarbon dating of charcoal from slag has proven that smelting has been carried out continuously in the Khasi hills of Meghalaya. The layer of this slag dates back to the period from $353 \, BCE$ to $128 \, CE$.

(N/A) The major ores of these metals are summarized in the table below:

Metal	Ores and Compositions
Aluminium	Bauxite: $AlO_x(OH)_{3-2x}$,Kaolinite: $[Al_2(OH)_4Si_2O_5]$
Iron	Haematite: $Fe_2O_3$,Magnetite: $Fe_3O_4$,Siderite: $FeCO_3$,Iron pyrites: $FeS_2$
Copper	Copper pyrites: $CuFeS_2$,Malachite: $CuCO_3 \cdot Cu(OH)_2$,Cuprite: $Cu_2O$,Copper glance: $Cu_2S$
Zinc	Zinc blende (Sphalerite): $ZnS$,Calamine: $ZnCO_3$,Zincite: $ZnO$

Aluminium is the most abundant metal in the Earth's crust,accounting for approximately $8.3 \%$ by weight. Iron is the second most abundant metal in the Earth's crust.

(N/A) $(i)$. Minerals: The naturally occurring chemical substances in which metals occur in the native or combined state are called minerals. Minerals are obtained through mining.
$(ii)$. Ores: The minerals from which a metal can be extracted profitably and conveniently are called ores.
$(iii)$. Metallurgy: The entire scientific and technological process used for the isolation of a metal from its ore is known as metallurgy.
$(iv)$. Gangue: The earthly or undesired impurities such as sand,rocky material,or limestone present in an ore are known as gangue.

(C) The common ores of copper are $CuFeS_2$ (Chalcopyrite),$Cu_2S$ (Chalcocite),and $Cu_2O$ (Cuprite).
The common ores of zinc are $ZnS$ (Zinc blende or Sphalerite),$ZnCO_3$ (Calamine),and $ZnO$ (Zincite).
Option $C$ lists the most industrially significant ores for both metals.

(A) The abundance of elements in the Earth's crust is as follows:
$1$. Oxygen $(O)$: $46.6\%$
$2$. Silicon $(Si)$: $27.7\%$
$3$. Aluminium $(Al)$: $8.1\%$
$4$. Iron $(Fe)$: $5.0\%$
Therefore,the second and third most abundant elements are Silicon and Aluminium,respectively.

(A) German silver is an alloy that does not contain silver. It is a mixture of approximately $60 \% \ Cu$,$20 \% \ Zn$,and $20 \% \ Ni$.

(A) Tin occurs mainly as cassiterite,$SnO_{2}$,and lead occurs mainly as galena,$PbS$.