Chemistry

The p-Block Elements.

Question:

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

Answer:

CIO has 17 + 8 +1 = 26 electrons.Also, OF2 has (8 + 2 x 9) = 26 electrons, and ClF has (17 + 9) = 26 electrons.Out of these, ClF can act as Lewis base. The chlorine atom has three lone pair of electrons which it donates to form compounds like ClF3, ClF5 and ClF7

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The p-Block Elements.

Q 1.

Discuss the trends in chemical reactivity of group 15 elements.

Q 2.

How is O3 estimated quantitatively?

Q 3.

Mention three areas in which H2SO4 plays an important role.

Q 4.

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

Q 5.

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

Q 6.

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

Q 7.

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

Q 8.

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

Q 9.

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

Q 10.

Which aerosols deplete ozone?

Q 11.

Write the reactions of F2 and Cl2 with water.

Q 12.

Mention three areas in which H2SO4 plays an important role.

Q 13.

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

Q 14.

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

Q 15.

Why are halogens strong oxidising agents?

Q 16.

List the uses of neoirand argon gases.

Q 17.

Write the structure of pyrophosphoric acid.

Q 18.

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

Q 19.

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 20.

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 21.

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 22.

Assertion (A): HI cannot be prepared by the reaction of KI with concentrated H2SO4.
Reason (R): HI has lowest H – X bond strength among halogen acids.

Q 23.

 Why is N2 less reactive at room temperature?

Q 24.

Why is bond angle in PH+4 ion higher than in PH3 ? (Pb. Board 2009)

Q 25.

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

Q 26.

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

Q 27.

Give the reason for bleaching action of Cl2.

Q 28.

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

Q 29.

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

Q 30.

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

Q 31.

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 32.

 List the uses of neoirand argon gases.

Q 33.

Why is N2 less reactive at room temperature?

Q 34.

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

Q 35.

Give the resonating structures of N02 and N2O5.

Q 36.

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

Q 37.

Which aerosols deplete ozone?

Q 38.

How is SO2 an air pollutant?

Q 39.

Explain why fluorine forms only one oxoacid, HOF.

Q 40.

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 41.

Which of the following pairs of ions are isoelectronic and isostructural?
ncert-exemplar-problems-class-12-chemistry-p-block-elements-6

Q 42.

Which of the following is correct for P4 molecule of white phosphorus?
(a) It has 6 lone pairs of electrons (b) It has six P – P single bonds
(c) It has three P – P single bonds (d) It has four lone pairs of electrons,

Q 43.

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 44.

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

Q 45.

SF6 is known but SCl6 is not. Why?

Q 46.

On reaction with Cl2, phosphorus forms two types of halides ‘A' and ‘B'. Halide A is yellowish-white powder but halide B' is colourless oily liquid. Identify A and B and write the formulas of their hydrolysis products.

Q 47.

White phosphorus reacts with chlorine and the product hydrolysis in the presence of water. Calculate the mass of HCl obtained by the hydrolysis of the product formed by the reaction of 62 g of white phosphorus with chlorine in the presence of water.

Q 48.

Phosphorus has three allotropic fonns —(i) white phosphorus (ii) red phosphorus and (iii) black phosphorus. Write the difference between white and red phosphorus on the basis of their structure and reactivity.

Q 49.

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 50.

Assertion (A): Both rhombic and monoclinic sulphur exist as S8 but oxygen exists as OÏ€.
Reason (R): Oxygen forms pπ-pπ multiple bond due to small size and small bond length but pπ-pπ bonding is not possible in sulphur.