Test: 35 Year JEE Previous Year Questions: The p-Block Elements

Alum furnishes Al³⁺ ions which bring about coagulation of negatively charged clay particles, bacteria etc.

In the formation of  XeF₂, sp³d hybridisation occurs which gives the molecule a trigonal bipyramidal structure.

In the formation of XeF₄, sp³d² hybridization occurs which gives the molecule an octahedral structure.

In the formation of XeF₆, sp³d³ hybridization occurs which gives the molecule a pentagonal bipyramidal structure.

NOTE :  In phosphorous the 3d- orbitals are available.
Hence phosphorous can from pentahalides also but nitrogen can not form pentahalide due to absence of dorbitals

hence oxidation no of Cl in OCl– is
–2 + x₂ = –1
x₂ = 2–1 = +1
now oxidation no. of another Cl is –1 as it is present as Cl^–.

On mixing phosphine with chlorine gas PCl₅ and HCl forms. The mixture cools down.
PH₃ + 4Cl₂ –––––→  PCl₅ + 3HCl

In graphite, carbon is sp² hybridized. Each carbon is thus linked to three other carbon atoms forming hexagonal rings. Since only three electrons of each carbon are used in making hexagonal ring, fourth electron of each carbon is free to move. This makes graphite a good conductors of heat and electricity.
Further graphite has a two dimensional sheet like structure. These various sheets are held together by weak van der Waal’s force of attraction. due to these weak forces of attraction, one layer can slip over the other. This makes graphite soft and a good lubricating agent.

Glass is a translucent or transparent amorphous supercooled solid solution or we can say super cooled liquid of silicates and borats having a general formula R₂O. MO. 6 SiO₂. where R = Na or K and M = Ca, Ba, Zn or Pb.

Among  the given compounds, the  is most basic. Hence has highest proton affinity

It is mer cury because it exists as liquid at room temperature.

Fluorine is the strongest oxidizing agent due to low heat of dissociation and high heat of hydration which compensate the lower value of electron affinity.

Property of He -It is used in weather balloons and tires of airplanes as He is non inflammable. He is heavier than H. So the correct option is c.

The maximum valency of beryllium is +2 while that of aluminium is +3.

Hypophosphorous acid 

The H–X bond strength decreases from HF to HI. i.e.
HF > HCl > HBr > HI. Thus HF is most stable while HI is least stable. This is evident from their decomposition reaction: HF and HCl are stable upto 1473K, HBr decreases slightly and HI dissociates considerably at 713K. The decreasing stability of the hydrogen halide is also reflected in the values of dissociation energy of the H–X bond

The solution of aluminium chloride in water is acidic due to hydrolysis.        

AlCl₃ + 3H₂O –––––→ Al(OH)₃ +  3HCl.
On heating  it till dryness Al(OH)₃ is converted into Al₂O₃

In SiO₂ (quartz), each of O-atom is shared between two SiO₄^4– tetrahedra

In diborane structure B₂H₆ there are two 2c-2e bonds and two 3c–2e bonds (see structure of diborane).
Structure of B₂H₆ :

The   is stronger than  The more the oxidation state of N, the more is the acid character.

The correct order of ionisation enthalpies is

F > P > S > B

NOTE : On moving along a period ionization enthalapy increases from left to right and decreases from top to bottom in a group. But this trend breaks up in case of atom having  fully or half filled stable orbitals.
In this case P has a stable half filled electronic configuration hence its ionisation enthalapy is greater in comparision to S. Hence the correct order is

B <  S < P < F.

During disproportionation same compound undergo simultaneous oxidation and reduction.

Chlorine reacts with excess of ammonia to produce ammonium chloride and nitrogen.

(NH₄)₂SO₄ + 2H₂O → 2H₂SO₄ + NH₄OH H₂SO₄ is strong acid and increases the acidity of soil.

The correct formula of inorganic benzene is B₃N₃H₆ so (d) is incorrect statement

Boric acid  is a lewis acid so (a) is
incorrect statement.
The coordination number exhibited by beryllium is 4 and not 6 so statement (b) is incorrect.
Both BeCl₂ and AlCl₃ exhibit bridged structures in solid state so (c) is correct statement.

The products of the concerned reaction react each other forming back the reactants.

XeF₆ + 3H₂O → XeO₃+ 6HF .

The ease of for mation an d stability  of hydrides decreases rapidly from NH3 to BiH₃. This is evident from their dissociation temperature which decreases from NH₃ to BiH₃. As we go down the group the size of central atom increases and thus metal-hydrogen bond becomes weaker due to decreased overlap between the large central atom and small hydrogen atom.

Oxidation of sulphur varies from – 2 to + 6 in its various compounds

Boron cannot form BF₆^3– due to non-availability of d-orbitals.

All the members form volatile halides of the type AX₃.  All  halides are pyramidal in shape.  The bond angle decreases on moving  down the group due to decrease in bond pair-bond pair repulsion.

Acidic strength increases as the oxidation number of central atom increases.
Hence acidic strength order is  

(+7)         (+5)         (+3)        (+1)
HClO4 > HClO3 > HClO2 > HClO

Nitric oxide is par amagn etic in th e gaseous state because of the presence of one unpaired electron in its outermost shell.
The electronic configuration of NO is

CsI3 dissociates as

CsI₃ → Cs⁺ + I₃^–

ICl

Order of reactivity of halogens
Cl₂ > Br₂> I₂

But, the interhalogen compounds are generally more reactive than halogens (except F₂), since the bond between two dissimilar electronegative elements is weaker than the bond between two similar atoms i.e, X – X

Nitrogen and oxgen in air do not react to form oxides of nitrogen in atmosphere because the reaction between nitrogen and oxygen  requires high temperature.

Xe. As we move down the group, the melting and boiling points show a regular increase due to corresponding increase in the magnitude of their van der waal forces of attraction as the size of the atom increases.

Phosphorous acids contain P in + 3 oxidation state.