Chemistry

The p-Block Elements.

Question:

 Why do noble gases have comparatively large atomic size?

Answer:

 The members of the noble gas family have comparatively large atomic size as compared to rest of the members present in the same period. Actually, for these elements, van der Waals’ radii are considered while for rest of the elements either covalent radii or metallic radii are taken into account. Since van der Waals’ radii arise simply due to van der Waals’ forces of attraction, these are expected to have comparatively large magnitude.

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The p-Block Elements.

Q 1.

How is O3 estimated quantitatively?

Q 2.

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

Q 3.

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

Q 4.

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

Q 5.

Discuss the trends in chemical reactivity of group 15 elements.

Q 6.

Match the items of Column I and Column II and mark the correct option.
ncert-exemplar-problems-class-12-chemistry-p-block-elements-49
ncert-exemplar-problems-class-12-chemistry-p-block-elements-50

Q 7.

Complete the following reactions:
(i)C2H2 + O2 -> (ii) 4Al + 3 O2 ->

Q 8.

Mention three areas in which H2SO4 plays an important role.

Q 9.

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

Q 10.

Justify the placement of O, S, Se, Te and Po in the same group’of the periodic table in terms of electronic configuration, oxidation state and hydride formation.

Q 11.

Explain why fluorine forms only one oxoacid, HOF.

Q 12.

Write a balanced equation for the hydrolytic reaction of PC is in heavy water.

Q 13.

What happens when H3PO4 is heated?

Q 14.

In the preparation of H2S06 by contact process, why is S03 not absorbed directly in water to form H2S04?

Q 15.

Out of H2O and H2S, which one has higher bond angle and why?

Q 16.

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

Q 17.

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 18.

Assertion (A): HNO3 makes from passive.
Reason (R): HNO3 forms a protective layer of ferric nitrate on the surface of iron.

Q 19.

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

Q 20.

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

Q 21.

Why has it been difficult to study the chemistry of radon?

Q 22.

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

Q 23.

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

Q 24.

Why is dioxygen a gas but sulphur a solid?

Q 25.

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

Q 26.

Give the resonating structures of N02 and N2O5.

Q 27.

Write main differences between the properties of white phosphorus and red phosphorus.

Q 28.

Why does nitrogen show catenation properties less than phosphorus?

Q 29.

Why are halogens strong oxidising agents?

Q 30.

Reduction potentials of some ions are given below. Arrange them in decreasing order of oxidizing power.
ncert-exemplar-problems-class-12-chemistry-p-block-elements-18

Q 31.

Write a balanced chemical equation, for the reaction showing catalytic oxidation of NH3 by atmospheric oxygen.

Q 32.

Write the structure of pyrophosphoric acid.

Q 33.

Phosphorus forms a number of oxoacids. Out of these oxoacids phosphinic acid has strong reducing property. Write its structure and also write a reaction showing its reducing behaviour.

Q 34.

 What is the covalence of nitrogen in N2O5 ?

Q 35.

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

Q 36.

 What happens when PCl5 is heated?

Q 37.

What is the basicity of H3PO4?

Q 38.

 List the important sources of sulphur.

Q 39.

Give two examples to show the anomalous behaviour of fluorine.

Q 40.

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

Q 41.

Discuss the trends in chemical reactivity of group 15 elements.

Q 42.

Give the resonating structures of N02 and N2O5.

Q 43.

Explain why NH3 is basic while BiH3 is only feebly basic.

Q 44.

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

Q 45.

Which aerosols deplete ozone?

Q 46.

 How are XeOand XeOF4prepared?

Q 47.

 List the uses of neoirand argon gases.

Q 48.

Why are pentahalides more covalent than trihalidcs ?

Q 49.

How does ammonia react with a solution of Cu2+?

Q 50.

Why does O3 act as a powerful oxidising agent?