Which one of the following is paramagnetic in nature?
✓
$NO$
B
$\mathrm{N}_2 \mathrm{O}$
C
$\mathrm{N}_2 \mathrm{O}_5$
D
All of the above
Answer
Correct option: A.
$NO$
Whenever two electrons are paired together in an orbital, or their total spin is $0$, they are diamagnetic electrons. Atoms with all diamagnetic electrons are called diamagnetic atoms.
A paramagnetic electron is an unpaired electron. $NO$ has one unpaired electron. Hence, it is paramagnetic in nature.
Which among the following substances is not a component of the mixture used for glazing pottery?
✓
Feldspar
B
Silica
C
Borax
D
Alumina
Answer
Correct option: A.
Feldspar
Ceramic glaze is an impervious layer or coating of a vitreous substance which has been fused to a ceramic body through firing. Glaze can serve to colour, decorate or waterproof an item.
Pottery glaze is made up of five basic components. These components are silica, alumina, flux, colourants and modifiers.
Borax bead test is used to identify the coloured metal ions in given salt. The coloured metal ions form their corresponding metaborate with boron and their colour used to identify them.
Electronic configuration of only one $p-$block element is exceptional. One molecule of that element consists of how many atoms of it?
✓
One
B
Two
C
Three
D
Four
Answer
Correct option: A.
One
The electronic configuration of an only $p-$block element is exceptional. One molecule of that element consists of only one atom of it.
As the exception is found in only He, as helium has the electronic configuration to be $1s^2$. But other member of the same group has $\ce{ns^2np^6}$ configuration.
So, this is an exceptional case where He does not resemble its group in its configuration.
And as He is a noble gas element so it is monoatomic gas.
Which of the following oxides is acidic in nature?
✓
$ \mathrm{B}_2 \mathrm{O}_3 $
B
$ \mathrm{Al}_2 \mathrm{O}_3$
C
$ \mathrm{Ga}_2 \mathrm{O}_3 $
D
$ \mathrm{In}_2 \mathrm{O}_3 $
Answer
Correct option: A.
$ \mathrm{B}_2 \mathrm{O}_3 $
$ \mathrm{B}_2 \mathrm{O}_3 $ is acidic in nature. It reacts with basic oxides to form metal borates. Acidic nature decreases on moving down the group.
The hydrides of the first elements in groups $15 - 17$, namely $\ce{NH3,H2O}$ and $HF$ respectively, show abnormally high values for melting and boiling points. This is due to:
A
Small size of $N, O$ and $F$
✓
The ability to form extensive intermolecular $H-$bonding
C
The ability to form extensive intramolecular $H-$bonding
D
Effective van der Waal's interaction
Answer
Correct option: B.
The ability to form extensive intermolecular $H-$bonding
The hydrides of the first elements in groups $15 - 17$, namely $\ce{NH_3, H_2O}$ and $HF$ respectively, show abnormally high values for melting and boiling points. This is due to the ability to form extensive inter$-$molecular $H-$bonding. In these hydrides, $H$ atom is attached to highly electronegative $N, O$ or $F$ atoms resulting in stronger hydrogen bonds which lead to molecular associations. Large amount of energy is needed to break these hydrogen bonds.
Which element has the highest valency with respect to oxygen?
A
Sodium
B
Aluminium
✓
Chlorine
D
Sulphur
Answer
Correct option: C.
Chlorine
The valence of an element with respect to oxygen is twice the number of oxygen atoms with which one atom of that element chemically combines.
The valency of chlorine with respect to oxygen is $7$.
Elements of group $14$ used in semiconductors are:
A
$\text{C, Si, Ge}$
B
$\text{Si, Ge, Sn}$
✓
$\text{Si, Ge}$
D
$\text{B, Si, Ge}$
Answer
Correct option: C.
$\text{Si, Ge}$
Silicon is found in the basis of all electronic devices. It is a semiconductor.
Germanium is another element used in semiconductors.
Ultrapure form of $Ge$ and $Si$ are used to make translators and semi conductors.
Cement, the important building material is a mixture of oxides of several elements. Besides calcium, iron and sulphur, oxides of elements of which of the group $(s)$ are present in the mixture?
A
group $2$.
✓
groups $2, 13$ and $14$.
C
groups $2$ and $13.$
D
groups $2$ and $14.$
Answer
Correct option: B.
groups $2, 13$ and $14$.
Cement is manufactured by combining substances which are lime$\text{(CaO)}$, clay contains silica $\text{(SiO)}$ and oxides of $Al, Mg$ and iron.
Reaction of ammonia with diborane gives initially $\mathrm{B}_2 \mathrm{H}_6 \cdot 2 \mathrm{NH}_3$ which on further heating gives:
✓
Borazine.
B
Borax.
C
Boric acid.
D
All of these.
Answer
Correct option: A.
Borazine.
Reaction of ammonia with diborane gives initially $\mathrm{B}_2 \mathrm{H}_6 \cdot 2 \mathrm{NH}_3$ which is formulated as $\left[\mathrm{BH}_2\left(\mathrm{NH}_3\right)_2\right]^{+}$. $\left[\mathrm{BH}_4\right]^{-}$further heating gives borazine, $\mathrm{B}_3 \mathrm{N}_3 \mathrm{H}_6$ known as "inorganic benzene" in view of its ring structure with alternate $BH$ and $NH$ groups.
Which element froms maximum compound in chemistry?
A
$O$
B
$H$
C
$Si$
✓
$C$
Answer
Correct option: D.
$C$
Carbon is the element which forms the highest number of compounds especially organic compounds due to its catenation $($long chain formation$)$ ability. Carbon, with $4$ valence atoms and by virtue of being small in size is most suited to form the highest number of compounds.
Quartz is the second most abundant mineral in the Earth's continental crust, after feldspar. Its crystal structure is a continuous framework of $\ce{SiO_4}$ silicon$–$oxygen tetrahedral, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of $\ce{SiO_2}$. Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent, $U.V$. light can pass through quartz.
Among $\ce{III-A}$ group elements, the elements with highest and lowest $I.P$. values are:
A
$B, Tl$
✓
$B, In$
C
$B, Al$
D
$B, Ga$
Answer
Correct option: B.
$B, In$
$I.P$. does not smoothly decrease down in $\text{III−A}$ group. The decrease from $B$ to $Al$ is associated with increase in size. The observed discontinuity in the $I.P.$ values between $Al$ and $Ga$, and between In and $Tl$ are due to the inability of $d-$ and $f-$electrons, which have low screening effect to compensate the increase in nuclear charge.
In the electrothermal process, the compound displaced by silica from calcium phosphate is:
A
Calcium
B
Phosphine
C
Phosphorus
✓
Phosphorus pentoxide
Answer
Correct option: D.
Phosphorus pentoxide
In the electrothermal process, the compound displaced by silica from calcium phosphate is phosphorus pentoxide. It is then reduced by coke in electric furnace to get white phosphorus.
$\mathrm{Ca}_3\left(\mathrm{PO}_4\right)_2+{ }_3 \mathrm{SiO}_2 \rightarrow{ }_3 \mathrm{CaSiO}_3+\mathrm{P}_2 \mathrm{O}_5$
When the glossy bead is dipped in metal oxide and heated, the corresponding metal metaborates are formed.
The characteristic colour of these metaborates enables us to identify the metal.
In which of the following the inert pair effect is most prominent ?
A
$C$
B
$Ge$
C
$Si$
✓
$Pb$
Answer
Correct option: D.
$Pb$
Due to poor or ineffective shielding of the $ns^2$ electrons of the valence shell by intervening d$-$ and f$-$electrons, the $s-$electrons are reluctant to participate in bond formation.
$\ce{CO_2}$ is gas, while $\ce{SiO_2}$ is solid because:
A
$\mathrm{CO}_2$ is a linear molecule, while $\mathrm{SiO}_2$ is angular.
B
van der Waals' forces are very strong in $\mathrm{SiO}_2$.
C
$\mathrm{CO}_2$ is covalent, while $\mathrm{SiO}_2$ is ionic.
✓
$Si$ cannot form stable bonds with $O$, hence $Si$ has to form a $3D$ lattice.
Answer
Correct option: D.
$Si$ cannot form stable bonds with $O$, hence $Si$ has to form a $3D$ lattice.
$\ce{SiO_2}$ is solid because $Si$ cannot form stable bonds with $O$, hence $Si$ has to form a $3D$ lattice of $\ce{SiO_2}$ molecules and form solid structure.
A compound $X$, of boron reacts with $\ce{NH_3}$ on heating to give another compound $Y$ which is called inorganic benzene. The compound $X$ can be prepared by treating $\ce{BF_3}$ with Lithium aluminium hydride. The compounds $X$ and $Y$ are represented by the formulas.
Which of the following member of the carbon family does not have an allotrope?
A
$Si$
B
$Sn$
C
$C$
✓
$Ge$
Answer
Correct option: D.
$Ge$
In carbon family only carbon, silicon and tin forms allotrope. Carbon has multiple allotrope, Silicon has two known allotropes that exist at room temperature and Tin also has two allotropes.Ge does not have an allotrope.
Solid $\mathrm{CO}_2$ is called dry ice becaouse it is used for making ice bath for organic reaction in laboratory. It is prepared by cooling $\mathrm{CO}_2$ gas at high pressure.
Boric acid is not a protonic acid but it acts as a Lewis acid by:
✓
Accepting electrons from a hydroxyl ion.
B
Donating electrons to a chloride ion.
C
Donating electrons to a proton.
D
Accepting proton from water.
Answer
Correct option: A.
Accepting electrons from a hydroxyl ion.
Boric acid is not a protonic acid, but it acts as a Lewis acid by accepting electrons from a hydroxyl ion.
$\text{B(OH)}_3+2\text{HOH}\xrightarrow{\ \ \ \ \ \ \ }[\text{B}(\text{OH})_4]^-+\text{H}_3\text{O}^+$.