Chemistry

The p-Block Elements.

Question:

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

Answer:

Nitrogen does not have vacant d-orbitals on its valence shell. Therefore, it cannot extend its dπ-pπ bonding is not possible. As a result, the molecules of R3N = 0 does not exist. However, phosphorus and rest of the members of the group 15 have vacant d-orbitals in the valence shell which can be involved in dπ-pπ bonding. Under the circumstances, R3P=0 molecule can exist.

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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.

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

Q 7.

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 8.

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 9.

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

Q 10.

Mention three areas in which H2SO4 plays an important role.

Q 11.

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

Q 12.

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

Q 13.

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 14.

Explain why fluorine forms only one oxoacid, HOF.

Q 15.

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

Q 16.

What happens when H3PO4 is heated?

Q 17.

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 18.

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

Q 19.

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

Q 20.

Write the structure of pyrophosphoric acid.

Q 21.

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

Q 22.

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 23.

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

Q 24.

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.

Q 25.

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

Q 26.

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

Q 27.

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

Q 28.

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

Q 29.

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

Q 30.

Why is dioxygen a gas but sulphur a solid?

Q 31.

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

Q 32.

Give the resonating structures of N02 and N2O5.

Q 33.

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

Q 34.

Why does nitrogen show catenation properties less than phosphorus?

Q 35.

Why are halogens strong oxidising agents?

Q 36.

A brown ring is formed in the ring test for NO3 ion. It is due to the formation of
ncert-exemplar-problems-class-12-chemistry-p-block-elements-10

Q 37.

PH3 forms bubbles when passed slowly in water but NH3 dissolves. Explain.

Q 38.

 What is the covalence of nitrogen in N2O5 ?

Q 39.

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

Q 40.

 What happens when PCl5 is heated?

Q 41.

What is the basicity of H3PO4?

Q 42.

 List the important sources of sulphur.

Q 43.

Give two examples to show the anomalous behaviour of fluorine.

Q 44.

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

Q 45.

Discuss the trends in chemical reactivity of group 15 elements.

Q 46.

Give the resonating structures of N02 and N2O5.

Q 47.

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

Q 48.

Which aerosols deplete ozone?

Q 49.

 How are XeOand XeOF4prepared?

Q 50.

 Why do noble gases have comparatively large atomic size?