Type of solid and Their properties Questions in English

(C) $O_2$ is paramagnetic.
Benzene and water are diamagnetic.
$Fe$ (Iron) is ferromagnetic.

(A) Scanning electron microscopy $(SEM)$ is a technique used to image the surface of a sample by scanning the surface with a focused beam of electrons.
It provides detailed information about the topography and morphology (structure) of the material surface.
Therefore,the correct option is $A$.

(D) Ceramic materials,specifically high-temperature superconductors like $YBa_2Cu_3O_7$,exhibit superconductivity at temperatures significantly higher than conventional metallic superconductors.
While many ceramic superconductors operate in the range of $90 \ K$ to $150 \ K$,the specific context of this question refers to the discovery of materials that show superconductivity at temperatures around $150 \ K$.
Therefore,the correct option is $D$.

(D) Silicon belongs to group $14$ and gallium belongs to group $13$.
When $Si$ is doped with $Ga$,a $p$-type semiconductor is produced.
This is because group $13$ elements have only $3$ valence electrons,while group $14$ elements have $4$.
This creates an electron-deficient bond or an electron vacancy (hole) in the crystal lattice.
These holes can move through the crystal like a positive charge,giving rise to electrical conductivity.

(B) $MnO$ exhibits antiferromagnetism.
They have a domain structure similar to ferromagnetic substances,but their domains are oppositely oriented and cancel out each other's magnetic moment.

(D) Some transition metal oxides exhibit electrical conductivity similar to metals.
Specifically,$TiO$,$CrO_{2}$,and $ReO_{3}$ are known to behave like metals in terms of their electrical properties.

(D) The correct matches are as follows:
$P$. Molecular solid: $H_2O$ $(iii)$
$Q$. Ionic solid: $MgO$ $(iv)$
$R$. Metallic solid: $Mg$ $(ii)$
$S$. Network solid: $SiC$ $(i)$
Therefore,the correct sequence is $P-iii, Q-iv, R-ii, S-i$.

(C) In quartz $(SiO_2)$,the lattice points are occupied by silicon and oxygen atoms,which are held together by a continuous network of covalent bonds.
Therefore,quartz is classified as a covalent or network crystal.

(C) Statement $(C)$ is incorrect.
Amorphous solids are isotropic in nature,meaning their physical properties (such as electrical conductivity or refractive index) are the same in all directions.
Crystalline solids,on the other hand,are anisotropic.

(D) network crystalline solid,also known as a covalent network solid,consists of atoms linked by a continuous network of covalent bonds throughout the crystal.
$NaCl$ is an ionic solid.
$Ice$ is a molecular solid held by hydrogen bonds.
$I_2$ is a molecular solid held by London dispersion forces.
$AlN$ (Aluminum Nitride) is a covalent network solid with a wurtzite-like structure.
Therefore,the correct option is $(D)$.

(C) In dry ice (solid $CO_2$),the constituent particles are molecules.
These molecules are held together by weak intermolecular forces such as London dispersion forces or dipole-dipole interactions.
Therefore,it is classified as a molecular crystal.
Rock salt $(NaCl)$ is an ionic crystal,while quartz $(SiO_2)$ and diamond $(C)$ are covalent (network) crystals.

(C) $Ag$ is a metallic solid.
$ZnS$ is an ionic solid.
$CO_{2(s)}$,$SO_{2(s)}$,$HCl_{(s)}$,and $H_2O_{(s)}$ are molecular solids (Total = $4$).
$SiO_2$ and $AlN$ are network solids (Total = $2$).
Therefore,the number of molecular solids is $4$ and the number of network solids is $2$.

(A) Molecular solids are composed of molecules held together by weak van der Waals' forces or hydrogen bonds.
Because of these weak intermolecular forces,molecular solids are generally soft and have low melting points.
Many molecular solids are also volatile in nature.
Therefore,the correct option is $A$.

(B) $1$. $SiO_2$ is a covalent network solid,which is an insulator and has a very high melting point. This is correct.
$2$. $MgO$ is an ionic solid,not a covalent solid. It consists of $Mg^{2+}$ and $O^{2-}$ ions held together by strong electrostatic forces of attraction. It is an insulator in the solid state and has a high melting point. Therefore,the description 'covalent solid' for $MgO$ is incorrect.
$3$. $H_2O_{\text{(ice)}}$ is a molecular solid held by hydrogen bonding,which is an insulator and has a low melting point. This is correct.
$4$. $Ag_{(s)}$ is a metallic solid,which is a conductor of electricity and has a high melting point. This is correct.
Thus,the incorrect set is $B$.

(A) The correct matching is based on the magnetic properties of the given substances:
$(A)$ Ferromagnetic: $CrO_2$ is a well-known ferromagnetic substance.
$(B)$ Antiferromagnetic: $MnO$ exhibits antiferromagnetism due to the alignment of magnetic moments in opposite directions.
$(C)$ Ferrimagnetic: $Fe_3O_4$ (magnetite) is a classic example of a ferrimagnetic substance.
$(D)$ Paramagnetic: $O_2$ is paramagnetic due to the presence of unpaired electrons in its molecular orbitals.
Therefore,the correct sequence is $A-2, B-3, C-4, D-1$.

(B) Dry ice is the solid form of $CO_2$.
It is a molecular crystal that undergoes sublimation at atmospheric pressure.

(C) Silicon is a group $14$ element. When it is doped with a group $15$ element like phosphorus,it has one extra electron compared to the silicon atoms. This excess electron makes it an $n$-type semiconductor.

(B) $Quartz$ is a piezoelectric material.
Piezoelectric materials develop an electric charge due to the displacement of ions or movement of electrons upon the application of mechanical stress.

(A) $SiO_2$ (quartz) is a covalent network solid that forms a continuous three-dimensional network of tetrahedral $SiO_4$ units linked by shared oxygen atoms.
$MgO$,$CaF_2$,and $ZnS$ are examples of ionic solids.

(D) Molecules are the constituent particles of molecular solids. These are further subdivided into three categories: $1$. Non-polar molecular solids,$2$. Polar molecular solids,$3$. Hydrogen-bonded molecular solids. $HCl$,$H_2O$ (ice),and $CCl_4$ are examples of molecular solids.
Silicon dioxide $(SiO_2)$ is a covalent or network solid. In this structure,each silicon atom is covalently bonded in a tetrahedral manner to four oxygen atoms. Each oxygen atom is further bonded to another silicon atom,creating a giant three-dimensional network. Therefore,it is not a molecular solid.

(A) The correct matching is as follows:
$(A)$ Metallic solid: $Cu$ $(4)$
$(B)$ Ionic solid: $NaCl$ $(3)$
$(C)$ Molecular solid: Ice $(2)$
$(D)$ Covalent (Network) solid: Diamond $(1)$
Therefore,the correct sequence is $A-4, B-3, C-2, D-1$.

(D) The given unit cell has atoms at all the corners and at two opposite face centres.
Thus,it is an end-centred unit cell.

(A) Piezoelectric materials are materials that have the ability to generate an internal electrical charge from applied mechanical stress.
Quartz $(SiO_2)$ is a well-known example of a piezoelectric material.
Hence,option $(A)$ is correct.

(D) Germanium $(Ge)$ belongs to group $14$ of the periodic table.
To create a $p$-type semiconductor,we need to dope it with an element from group $13$,which has one less valence electron than $Ge$.
This creates an electron-deficient bond or a 'hole',which acts as a positive charge carrier.
Among the given options,$Bi$,$Sb$,and $As$ belong to group $15$ (which would create an $n$-type semiconductor),while $Ga$ belongs to group $13$.
Therefore,doping $Ge$ with $Ga$ results in a $p$-type semiconductor.

(C) When silicon $(Si)$ is doped with an impurity having a valency less than $4$,a $p$-type semiconductor is obtained.
Silicon belongs to group $14$ and has a valency of $4$.
Elements like $As$ (Arsenic),$P$ (Phosphorus),and $Sb$ (Antimony) belong to group $15$ and have a valency of $5$,which results in $n$-type semiconductors.
$In$ (Indium) belongs to group $13$ and has a valency of $3$.
Therefore,doping $Si$ with $In$ creates electron holes,resulting in a $p$-type semiconductor.

(C) Metals are good conductors of electricity due to the presence of free electrons.
Electrical conductivity of semiconductors increases with an increase in temperature.
Silicon doped with boron (Group $13$ element) creates a $p$-type semiconductor.
Silicon doped with arsenic (Group $15$ element) creates an $n$-type semiconductor.

(C) In ferrimagnetic substances,the magnetic moments of the domains are aligned in parallel and antiparallel directions in unequal numbers.
The net magnetic moment is non-zero but small.
These substances are weakly attracted by a magnetic field compared to ferromagnetic substances and lose their ferrimagnetism on heating,becoming paramagnetic.
Examples include $Fe_3O_4$ (magnetite) and ferrites like $MgFe_2O_4$ and $NiFe_2O_4$.
Among the given compounds:
$1$. $Fe_3O_4$: Ferrimagnetic
$2$. $MgFe_2O_4$: Ferrimagnetic
$3$. $NiFe_2O_4$: Ferrimagnetic
$4$. $MnO$: Antiferromagnetic
$5$. $CrO_2$: Ferromagnetic
Thus,there are $3$ compounds that show ferrimagnetism.
Therefore,option $C$ is the correct answer.

(A) Based on the magnetic domain alignments:
$1$. Antiferromagnetism $(A)$ shows equal and opposite alignment of magnetic moments,resulting in zero net magnetic moment. This corresponds to $I$ $(\uparrow \downarrow \uparrow \downarrow \uparrow \downarrow)$.
$2$. Ferromagnetism $(B)$ shows all magnetic moments aligned in the same direction,resulting in a large net magnetic moment. This corresponds to $II$ $(\uparrow \uparrow \uparrow \uparrow \uparrow \uparrow)$.
$3$. Ferrimagnetism $(C)$ shows unequal and opposite alignment of magnetic moments,resulting in a net magnetic moment. This corresponds to $III$ $(\uparrow \uparrow \downarrow \uparrow \uparrow \downarrow)$.
Therefore,the correct match is $A-I, B-II, C-III$.