Chemistry

The p-Block Elements.

Question:

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

Answer:

Down the group, the atomic size of the element (E) increases and the bond length of the corresponding E—H bond also increases. This adversely affects the bond dissociation enthalpy. This means that amongst the trihydrides of the members of nitrogen family, the bond dissociation enthalpy of Bi—H bond is the least. Therefore, BiH3 is the strongest reducing agent among the hydrides of group 15 elements.

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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.

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 5.

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

Q 6.

Mention three areas in which H2SO4 plays an important role.

Q 7.

Explain why fluorine forms only one oxoacid, HOF.

Q 8.

What happens when H3PO4 is heated?

Q 9.

Discuss the trends in chemical reactivity of group 15 elements.

Q 10.

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

Q 11.

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 12.

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

Q 13.

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

Q 14.

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

Q 15.

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

Q 16.

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

Q 17.

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

Q 18.

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

Q 19.

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 20.

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

Q 21.

Give the resonating structures of N02 and N2O5.

Q 22.

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

Q 23.

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 24.

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

Q 25.

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

Q 26.

Write the structure of pyrophosphoric acid.

Q 27.

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

Q 28.

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 29.

 What is the covalence of nitrogen in N2O5 ?

Q 30.

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

Q 31.

 What happens when PCl5 is heated?

Q 32.

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

Q 33.

Give two examples to show the anomalous behaviour of fluorine.

Q 34.

Discuss the trends in chemical reactivity of group 15 elements.

Q 35.

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

Q 36.

Why is dioxygen a gas but sulphur a solid?

Q 37.

Which aerosols deplete ozone?

Q 38.

 How are XeOand XeOF4prepared?

Q 39.

Why are pentahalides more covalent than trihalidcs ?

Q 40.

Why does O3 act as a powerful oxidising agent?

Q 41.

How is O3 estimated quantitatively?

Q 42.

Mention three areas in which H2SO4 plays an important role.

Q 43.

Why does the reactivity of nitrogen differ from phosphorus?

Q 44.

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

Q 45.

Why does R3P = O exist but R3N = O does not (R = alkyl group)?

Q 46.

Why does nitrogen show catenation properties less than phosphorus?

Q 47.

Describe the manufacture of H2SO4 by contact process?

Q 48.

Why are halogens strong oxidising agents?

Q 49.

Write the reactions of F2 and Cl2 with water.

Q 50.

Which one of the following does not exist ?
(i)XeOF4 (ii)NeF2
(iii)XeF4 (iv)XeF6