Chemistry

The p-Block Elements.

Question:

How are XeO3  and XeOF4prepared?

Answer:

ncert-solutions-for-class-12-chemistry-the-p-block-elements-23

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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.

Discuss the trends in chemical reactivity of group 15 elements.

Q 12.

Give the resonating structures of N02 and N2O5.

Q 13.

Why are halogens strong oxidising agents?

Q 14.

Write the reactions of F2 and Cl2 with water.

Q 15.

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

Q 16.

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

Q 17.

Give the reason for bleaching action of Cl2.

Q 18.

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

Q 19.

 Why are halogens strong oxidising agents?

Q 20.

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

Q 21.

 How are XeOand XeOF4prepared?

Q 22.

Why are pentahalides more covalent than trihalidcs ?

Q 23.

Why is N2 less reactive at room temperature?

Q 24.

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

Q 25.

List the important sources of sulphur.

Q 26.

Why does O3 act as a powerful oxidising agent?

Q 27.

How is O3 estimated quantitatively?

Q 28.

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

Q 29.

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

Q 30.

Write two uses of ClO2

Q 31.

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

Q 32.

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

Q 33.

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 34.

How does ammonia react with a solution of Cu2+?

Q 35.

 What happens when PCl5 is heated?

Q 36.

 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 37.

Which aerosols deplete ozone?

Q 38.

Write the reactions of F2 and Cl2 with water.

Q 39.

How does ammonia react with a solution of Cu2+?

Q 40.

What happens when PCl5 is heated?

Q 41.

How is the presence of SO2 detected ?

Q 42.

Why does nitrogen show catenation properties less than phosphorus?

Q 43.

Describe the manufacture of H2SO4 by contact process?

Q 44.

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

Q 45.

If chlorine gas is passed through hot NaOH solution, two changes are observed in the oxidation number of chlorine during the reaction. These are —— and ——-

Q 46.

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 47.

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 48.

Name three oxoacids of nitrogen. Write the disproportionation reaction of that oxoacid of nitrogen in which nitrogen is in +3 oxidation state.

Q 49.

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 50.

An amorphous solid "A"bums in air to form a gas "B"which turns lime water milky. The gas is also produced as a by-product during roasting of sulphide ore. This gas decolourises acidified aqueous KMnO4  solution and reduces Fe3+ to Fe+2. Identify the solid "A"and the gas "B"and write the reactions involved.