JEE Questions for Chemistry Class 12 P Block Elements Quiz 8 - MCQExams.com

Red P does not react with NaOH. Only white P reacts with NaOH or KOH to from PH₃.

Since As is less electronegative than P, therefore its oxides will be less acidic than those of P. However, higher the oxidation state of the element more acidic is the oxide. Thus As₄O₆ (where oxidation of As is + 3 ) is a weaker acid than As₄O₁₀ (where oxidation state of As is + 5 )

H₃PO₂ is named as hypophosphorous acid. As it contains only one P – OH group, its basicity is one.

Both P₄O₁₀ and P₂O₅  may be regarded as anhydrides of H₃PO₄ but since P₂O₅ occurs as a dimer so the right answer is P₄O₁₀ and not P₂O₅
P₄O₁₀ + 6H₂O → 4H₃PO₄

Both CN^‒ and N₂ are isoelctronic containing 10 valence electrons each but N₂ is chemically inert because of the presence of pure covalent bonds between identical atoms of similar electronegativity and thus there is no bond polarity. In case of CN^‒ ion the bond between C and N has some ionic character due to the difference in electronegativity of C and N. Thus due to this polartity in bonds, CN^‒ ion is more reactive.

Nitrogen is inert because it has large bond dissociation energy (946 kJ mol^-1 ).

Out of N, S and C, nitrogen has the highest electronegativity and it decrease in the order N > S > C. Thus the oxide of nitrogen in its highest (+ 5) oxidation state will the most acidic. Next to N₂O₅ in the decreasing order of acidity will be SO₂, then CO₂ and finally CO which is neutral.

B is sp²-hybridized in BCl₃ and has no lone pair of electrons whereas N is sp³ – hybridized in NCl₃ and has a lone pair of electrons due to which it has a pyramidal structure

H₅P₅O₁₅ is metaphosphoric acid which is pentameric i.e, (HPO₃)₅ and will give cyclic phosphate.

Cl^‒ ,S^2- ,P^3- are isoelectronic species. Their sizes increases as the nuclear charge decreases from Cl to P.

H₃CO₃ < H₃PO₄ < HCl < HI.

NaH₂PO₂ is derived from H₃PO₂ which is monobasic. Hence it is a neutral salt

B.P. follows this order.

Acidic strength decreases in the order Cl₂O₇ > SO₂ P₄O₁₀

In case of phosphorus, pπ  - pπ  bonding is weak and thus P₂ molecule is unstable.

Dipole moment of NH₃ is larger than NF₃. BF₃ has no dipole moment.

1 E₁ of N is higher than that of O due to exactly half filled (more symmetrical) electronic configuration of N which imparts realatively more stability to the atom.

Undecomposed AgBr forms a soluble complex with hypo
AgBr + 2Na₂S₂O₃ → Na₂ [Ag(s₂O₃ )₂ ] + NaBr
It is washed with water and the image is fixed.

(c) sulphuric acid

Na₂S₂O₃ + Cl₂ + H₂O → Na₂SO₄ + S + 2HCl

2Na₂S₂O₃ + I₂ → Na₂S₄O₆ + 2NaI
sod. tetrathionate (colourless)

BaO₂ + H₂SO₄ → BaSO₄ + H₂O₂
                Dil.
Here, in the products the most electronegative element is oxygen.
In BaSO₄ , O has an oxidation state -2 while in H₂O₂ it is -1.

Alkaline solution of pyrogallol absorbs oxygen quickly.

Final acid obtained by contact process in H₂S₂O₇ (oleum )

H₂S is acidic in aqueous solution because H - S bond is weaker and has more tendency to release a proton while H₂O is neutral because O – H bond is stronger and has a little tendency to release a proton.

Caro’s acid is H₂SO₅ which contains one S – O – OH peroxy linkage.

Ozone protects the earth’s inhabitants by abosorbing UV radiations and not gamma radiations.

Oxidation number of S in S₈ = 0, in S₂F₂ = + 1 and in H₂S = -2.

In the reaction 2 SO₂ + O₂ → 2 SO₃ , V₂O₅ acts as a catalyst.