Chemistry

The p-Block Elements.

Question:

 Why does nitrogen show catenation properties less than phosphorus ? (C.B.S.E. Foreign 2009)

Answer:

The valence shell electronic configuration of N is 2s22p3. In order to complete the octet, the two nitrogen atoms share three electron pairs in the valence p-sub-shell and get linked by triple bond (N=N). Thus molecular nitrogen exists as discrete diatomic species and there is no scope of any self linking or catenation involving a number of nitrogen atoms. However, in case of phosphorus, multiple bonding is not feasible due to comparatively large atomic size of the element. Molecular phosphorus exists as tetra-atomic molecule (P4) in white phosphorus. These tetrahedrons are further linked by covalent bonds to form red variety which is in polymeric form. Thus, catenation in nitrogen is less than in phosphorus.

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The p-Block Elements.

Q 1.

Write the conditions to maximise the yield of H2SO4 by Contact process.

Q 2.

 Write balanced equations for the following:
(i) NaCl is heated witlrsulphuric acid in the presence of MnO2
(ii) Chlorine gas is passed into a solution of Nal in water.

Q 3.

Which of the following statements are true?
(a) Only type of interactions between particles of noble gases are due to weak dispersion forces.
(b) Ionisation enthalpy of.molecular oxygen is very close to that of xenon.
(c) Hydrolysis of XeF6 is a redox reaction.
(d) Xenon fluorides are not reactive.

Q 4.

 Write two uses of ClO2

Q 5.

 Why do noble gases have comparatively large atomic size?

Q 6.

Write the order of thermal stability of the – hydrides of Group 16 elements.

Q 7.

Can PCl5 act as an oxidising as well as a reducing agent Justify.

Q 8.

In PCl5, phosphorus is in sp3d hybridised state but all its five bonds are not equivalent. Justify your answer with reason.

Q 9.

In the ring test of NO3 ion.Fe2+ion reduces nitrate ion to nitric oxide, which combines with Fe2+  (aq.) ion to form brown complex. Write the reactions involved in the formation of brown ring.

Q 10.

What happens when sulp’hur dioxide is passed through an aqueous solution of Fe(III) salt?

Q 11.

 Why does nitrogen show catenation properties less than phosphorus ? (C.B.S.E. Foreign 2009)

Q 12.

How is O3 estimated quantitatively?

Q 13.

Discuss the trends in chemical reactivity of group 15 elements.

Q 14.

How is nitrogen prepared in the laboratory? Write the chemical equations of the reactions . involved.

Q 15.

Give the resonating structures of N02 and N2O5.

Q 16.

Nitrogen exists as diatomic molecule and phosphorus as P4. Why?

Q 17.

Why are halogens strong oxidising agents?

Q 18.

Write the reactions of F2 and Cl2 with water.

Q 19.

With what neutral molecule is CIO isoelectronic? Is that molecule a Lewis base?

Q 20.

Explain why does the stability of oxoacids of chlorine increase in the order given below:
HClO < HClO2 < HClO3 < HClO4

Q 21.

On heating compound (A) gives a gas (B) which is a constituent of air. This gas when treated with 3 mol of hydrogen (H2   ) in the presence of a catalyst gives another gas (C) which is basic in nature. Gas C on further oxidation in moist condition gives a compound (D) which is a part of acid rain. Identify compounds (A) to (D) and also give necessary equations of all the steps involved. –

Q 22.

 Why is BiH3 the strongest reducing agent amongst all the hydrides of group 15 elements? (C.B.S.E. 2013)

Q 23.

 What happens when PCl5 is heated?

Q 24.

Give the reason for bleaching action of Cl2.

Q 25.

 Why does R3P=0 exist but R3N=0 does not (R is an alkyl group) ?

Q 26.

 Knowing the electron gain enthalpy values of O—>O and O—>O2- as -141 and 702 kJ mol-1 respectively, how can you account for the formation of a large number of oxides having O2- species and not O?

Q 27.

Which aerosols deplete ozone?

Q 28.

 Why are halogens strong oxidising agents?

Q 29.

Write the reactions of F2 and Cl2 with water.

Q 30.

 With which neutral molecule is ClO isoelectronic? Is this molecule Lewis acid or base ? (Pb. Board 2009)

Q 31.

 How are XeOand XeOF4prepared?

Q 32.

Why are pentahalides more covalent than trihalidcs ?

Q 33.

Why is N2 less reactive at room temperature?

Q 34.

How does ammonia react with a solution of Cu2+?

Q 35.

What happens when white phosphorus is heated with concentrated NaOH solution in an inert atmosphere of CO2 ?

Q 36.

List the important sources of sulphur.

Q 37.

Why does O3 act as a powerful oxidising agent?

Q 38.

Write two uses of ClO2

Q 39.

Which of the following statements are correct?
(a) All three N – O bond lengths in HNO3 are equal.
(b) All P – Cl bond lengths in PCl5 molecule in gaseous state are equal.
(c) P4  molecule in white phosphorus have angular strain therefore white phosphorus is very reactive.
(d) PCl5 is ionic in solid state in which cation is tetrahedral and anion is octahedral.

Q 40.

In which of the following reactions cone. H2S04 is used as an oxidizing reagent?
ncert-exemplar-problems-class-12-chemistry-p-block-elements-25

Q 41.

SF6 is known but SCl6 is not. Why?

Q 42.

Match the compounds given in Column I with the hybridization and shape given in Column II and mark the correct option.
ncert-exemplar-problems-class-12-chemistry-p-block-elements-44

Q 43.

How does ammonia react with a solution of Cu2+?

Q 44.

Why is bond angle in PH+4 ion higher than in PH3 ? (Pb. Board 2009)

Q 45.

 What happens when H3PO4 is heated?

Q 46.

Why does O3 act as a powerful oxidising agent?

Q 47.

Why is the reactivity of nitrogen different from that of phosphorus?

Q 48.

Discuss the trends in chemical reactivity of group 15 elements.

Q 49.

Give the resonating structures of N02 and N2O5.

Q 50.

Explain why inspite of nearly the same electronegativity, nitrogen forms hydrogen bonding while chlorine does not.