Chemistry

The p-Block Elements.

Question:

Why are pentahalides more covalent than trihalidcs ?

Answer:

The group 15 elements have 5  e-1 s in their valence shell. It is difficult to lose 3e-1s to form E3+ and even more difficult to lose 5e-1  s to form E5+. Thus, they have very little tendency to form ionic compounds. Further, since the elements in +5 state have less tendency to lose e-1s than in the +3 state, elements in +5 state have more tendency to share e-1  s and hence pentahalides are more covalent than trihalides.

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The p-Block Elements.

Q 1.

Give the reason for bleaching action of Cl2.

Q 2.

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

Q 3.

Why are halogens strong oxidising agents?

Q 4.

 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 5.

Describe the manufacture of H2SO4 by contact process?

Q 6.

How does ammonia react with a solution of Cu2+?

Q 7.

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

Q 8.

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

Q 9.

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

Q 10.

Give the resonating structures of N02 and N2O5.

Q 11.

Which of the following acid forms three series of salts?
(a) H2PO2  (b) H3BO3 (C)H3PO4(d)H3PO3

Q 12.

Match the formulas of oxides given in Column I with the type of oxide given in Column II and mark the correct option.
ncert-exemplar-problems-class-12-chemistry-p-block-elements-47

Q 13.

How is O3 estimated quantitatively?

Q 14.

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

Q 15.

Write two uses of ClO2

Q 16.

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 17.

 Why is N2 less reactive at room temperature?

Q 18.

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

Q 19.

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

Q 20.

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

Q 21.

How is the presence of SO2 detected ?

Q 22.

What inspired N. Bartlett for carrying out reaction between Xe and PtF6?

Q 23.

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

Q 24.

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 25.

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 26.

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

Q 27.

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

Q 28.

Which aerosols deplete ozone?

Q 29.

Why is N2 less reactive at room temperature?

Q 30.

Which of the following options are not in accordance with the properly mentioned against them?
ncert-exemplar-problems-class-12-chemistry-p-block-elements-20

Q 31.

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 32.

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

Q 33.

Give two examples to show the anomalous behaviour of fluorine.

Q 34.

Name two poisonous gases which can be prepared from chlorine gas

Q 35.

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

Q 36.

Why is dioxygen a gas but sulphur a solid?

Q 37.

 How is SO2 an air pollutant?

Q 38.

Explain why fluorine forms only one oxoacid, HOF.

Q 39.

 Write two uses of ClO2

Q 40.

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

Q 41.

 Why do noble gases have comparatively large atomic size?

Q 42.

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

Q 43.

Mention the conditions required to maximise the yield of ammonia.

Q 44.

What happens when H3PO4 is heated?

Q 45.

Why is H2O a liquid and H2S a gas ?

Q 46.

Which of the following does not react with oxygen directly?  Zn, Ti, Pt, Fe

Q 47.

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

Q 48.

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

Q 49.

Comment on the nature of two S-O bonds formed in S02 molecule. Are the two S-O bonds in this molecule equal ?

Q 50.

Mention three areas in which H2SO4 plays an important role.