p-Block Elements · JEE Main previous year questions

Given below are the statements about diborane (a) Diborane is prepared by the oxidation of $\mathrm{NaB}{\mathrm{H}}_4$ with ${\mathrm{I}}_2$ (b) Each boron atom is in $\mathrm{s}{\mathrm{p}}^2$ hybridized state (c) Diborane has one bridged 3 centre-2-electron bond (d) Diborane is a planar molecule The option with correct statements is :

1. A.(c) and (d) only
2. B.(a) only
3. C.(c) only
4. D.(a) and (b) only

Chemical nature of the nitrogen oxide compound obtained from a reaction of concentrated nitric acid and ${\text{P}}_4{\text{O}}_{10}$ (in $4:1$ ratio) is :

1. A.acidic
2. B.basic
3. C.amphoteric
4. D.neutral

The number of nitrogen atoms in a semicarbazone molecule of acetone is ______________.

The number of ionisable hydrogens present in the product obtained from a reaction of phosphorus trichloride and phosphonic acid is :

1. A.3
2. B.0
3. C.2
4. D.1

The chemical that is added to reduce the melting point of the reaction mixture during the extraction of aluminium is :

1. A.Cryolite
2. B.Bauxite
3. C.Calamine
4. D.Kaolite

Match List - I with List - II : $$\begin{array}{llll}& \text{List - I}& & \text{List - II}\\ & \text{Industrial process}& & \text{Application}\\ \text{(a)}& \text{Haber’s process}& \text{(i)}& \mathrm{HN}{\mathrm{O}}_3\text{ synthesis}\\ \text{(b)}& \text{Ostwald’s process}& \text{(ii)}& \text{Aluminium extraction}\\ \text{(c)}& \text{Contact process}& \text{(iii)}& \mathrm{N}{\mathrm{H}}_3\text{ synthesis}\\ \text{(d)}& \text{Hal-Heroult process}& \text{(iv)}& {\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4\text{ synthesis}\end{array}$$ Choose the correct answer from the options given below :

1. A.(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
2. B.(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
3. C.(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
4. D.(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)

The process that involves the removal of sulphur from the ores is :

1. A.Roasting
2. B.Smelting
3. C.Leaching
4. D.Refining

The presence of ozone in troposphere :

1. A.protects us from greenhouse effect
2. B.protects us from the UV radiation
3. C.protects us from the X-ray radiation
4. D.generates photochemical smog

3.12 g of oxygen is adsorbed on 1.2 g of platinum metal. The volume of oxygen adsorbed per gram of the adsorbent at 1 atm and 300 K in L is _________. $[R=0.0821\mathrm{L}\mathrm{atm}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}]$

In mildly alkaline medium, thiosulphate ion is oxidized by $Mn{O}_4^{-}$ to "A". The oxidation state of sulphur in "A" is _________.

The correct statement with respect to dinitrogen is :

1. A.${\mathrm{N}}_2$ is paramagnetic in nature
2. B.it can be used as an inert diluent for reactive chemicals
3. C.it can combine with dioxygen at $25^{\circ }\mathrm{C}$
4. D.liquid dinitrogen is not used in cryosurgery

The average molar mass of chlorine is $35.5\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$. The ratio of ${}^{35}\mathrm{Cl}$ to ${}^{37}\mathrm{Cl}$ in naturally occuring chlorine is close to :

1. A.$1:1$
2. B.$2:1$
3. C.$3:1$
4. D.$4:1$

1. A.(a), (c) and (d)
2. B.(b) and (c)
3. C.(c) and (d)
4. D.(a) and (d)

In a molecule of pyrophosphoric acid, the number of P - OH, P = O and P - O - P bonds/moiety(ies) respectively are :

1. A.4, 2 and 0
2. B.4, 2 and 1
3. C.3, 3 and 3
4. D.2, 4 and 1

The volume (in mL) of 0.1 N NaOH required to neutralise 10 mL of 0.1 N phosphinic acid is ___________.

1. A.
2. B.
3. C.
4. D.

The statement that is not true about ozone is :

1. A.In the stratosphere, CFCs release chlorine free radicals $(\mathrm{Cl})$ which reacts with ${\mathrm{O}}_3$ to give chlorine dioxide radicals
2. B.It is a toxic gas and its reaction with $\mathrm{NO}$ gives $\mathrm{N}{\mathrm{O}}_2$.
3. C.In the atmosphere, it is depleted by CFCs
4. D.In the stratosphere, it forms a protective shield against UV radiation

The shape / structure of $[\mathrm{Xe}{\mathrm{F}}_5{]}^{-}$ and $\mathrm{Xe}{\mathrm{O}}_3{\mathrm{F}}_2$, respectively, are

1. A.Pentagonal planar and trigonal bipyramidal
2. B.Trigonal bipyramidal and pentagonal planar
3. C.Octahedral and square pyramidal
4. D.Trigonal bipyramidal and trigonal bipyramidal

Two elements A and B have similar chemical properties. They don’t form solid hydrogencarbonates, but react with nitrogen to form nitrides. A and B, respectively, are :

1. A.Li and Mg
2. B.Cs and Ba
3. C.Na and Rb
4. D.Na and Ca

Amongst the following statements regarding adsorption, those that are valid are (a) $\Delta \mathrm{H}$ becomes less negative as adsorption proceeds (b) On a given adsorbent, ammonia is adsorbed more than nitrogen gas (c) On adsorption, the residual force acting along the surface of the adsorbent increases (d) With increase in temperature, the equilibrium concentration of adsorbate increases

1. A.(c) and (d)
2. B.(a) and (b)
3. C.(d) and (a)
4. D.(b) and (c)

If the magnetic moment of a dioxygen species is 1.73 B.M, it may be :

1. A.${\mathrm{O}}_2^{-}$ or ${\mathrm{O}}_2^{+}$
2. B.${\mathrm{O}}_2$, ${\mathrm{O}}_2^{-}$ or ${\mathrm{O}}_2^{+}$
3. C.${\mathrm{O}}_2$ or ${\mathrm{O}}_2^{+}$
4. D.${\mathrm{O}}_2$ or ${\mathrm{O}}_2^{-}$

1. A.B > D > A > C
2. B.D > B > C > A
3. C.B > A > D > C
4. D.B > D > C > A

The number of bonds between sulphur and oxygen atoms in ${\mathrm{S}}_2{\mathrm{O}}_8^{2-}$ and the number of bonds between sulphur and sulphur atoms in rhombic sulphur, respectively, are :

1. A.4 and 8
2. B.8 and 6
3. C.4 and 6
4. D.8 and 8

Kjeldahl's method cannot be used to estimate nitrogen for which of the following compounds?

1. A.${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{N}{\mathrm{H}}_2$
2. B.$\mathrm{N}{\mathrm{H}}_2-\mathrm{CON}{\mathrm{H}}_2$
3. C.${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{N}{\mathrm{O}}_2$
4. D.$\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2-\mathrm{C}\equiv \mathrm{N}$

A metal (A) on heating in nitrogen gas gives compound B. B on treatment with ${\mathrm{H}}_2\mathrm{O}$ gives a colourless gas which when passed through $\mathrm{CuS}{\mathrm{O}}_4$ solution gives a dark blue-violet coloured solution. A and B respectively, are :

1. A.$\mathrm{Na}$ and $\mathrm{NaN}{\mathrm{O}}_3$
2. B.$\mathrm{Na}$ and $\mathrm{N}{\mathrm{a}}_3\mathrm{N}$
3. C.$\mathrm{Mg}$ and $\mathrm{M}{\mathrm{g}}_3{\mathrm{N}}_2$
4. D.$\mathrm{Mg}$ and $\mathrm{Mg}(\mathrm{N}{\mathrm{O}}_3{)}_2$