Chemistry

The p-Block Elements.

Question:

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

Answer:

 Molecular nitrogen exists as a diatomic molecule (N2) in which the two nitrogen atoms are linked to each other by triple bond (N≡N). It is a gas at room temperature. Multiple bonding is not possible in case of phosphorus due to its large size. It exists as P4 molecule (solid) in which P atoms are linked to one another by single covalent bonds. Because of greater bond dissociation enthalpy (946 kJ mol-1) of N≡N bond, molecular nitrogen is very less reactive as compared to molecular 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.

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

Q 6.

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

Q 7.

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

Q 8.

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 9.

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

Q 10.

 Why do noble gases have comparatively large atomic size?

Q 11.

How is O3 estimated quantitatively?

Q 12.

Discuss the trends in chemical reactivity of group 15 elements.

Q 13.

Give the resonating structures of N02 and N2O5.

Q 14.

Why are halogens strong oxidising agents?

Q 15.

Write the reactions of F2 and Cl2 with water.

Q 16.

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

Q 17.

 What happens when PCl5 is heated?

Q 18.

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

Q 19.

Give the reason for bleaching action of Cl2.

Q 20.

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

Q 21.

 Why are halogens strong oxidising agents?

Q 22.

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

Q 23.

 How are XeOand XeOF4prepared?

Q 24.

Why are pentahalides more covalent than trihalidcs ?

Q 25.

Why is N2 less reactive at room temperature?

Q 26.

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

Q 27.

List the important sources of sulphur.

Q 28.

Why does O3 act as a powerful oxidising agent?

Q 29.

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

Q 30.

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

Q 31.

Write two uses of ClO2

Q 32.

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

Q 33.

SF6 is known but SCl6 is not. Why?

Q 34.

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

Q 35.

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 36.

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 37.

How does ammonia react with a solution of Cu2+?

Q 38.

 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 39.

Which aerosols deplete ozone?

Q 40.

Write the reactions of F2 and Cl2 with water.

Q 41.

How are xenon fluorides XeF2, XeF4 and XeFobtained?

Q 42.

Why is BiH3 the strongest reducing agent amongst all the hydrides of Group 15 elements?

Q 43.

How does ammonia react with a solution of Cu2+?

Q 44.

What happens when PCl5 is heated?

Q 45.

How is the presence of SO2 detected ?

Q 46.

Illustrate how copper metal can give different products on reaction with HN03.

Q 47.

Why does nitrogen show catenation properties less than phosphorus?

Q 48.

Describe the manufacture of H2SO4 by contact process?

Q 49.

How are XeO3  and XeOF4prepared?

Q 50.

In qualitative analysis when H2S is passed through an aqueous solution of salt acidified with dil. HCl, a black precipitate is obtained. On boiling the precipitate with dil. HNO3, it forms a solution of blue colour. Addition of excess of aqueous solution of ammonia to this solution gives
ncert-exemplar-problems-class-12-chemistry-p-block-elements-3