Chemistry

The p-Block Elements.

Question:

What happens when H3PO4 is heated?

Answer:

On heating, H3PO3  disproportionates to form PH3 and H3PO4 with O.S. of-3and + 5.
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The p-Block Elements.

Q 1.

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 2.

How is O3 estimated quantitatively?

Q 3.

 Why is N2 less reactive at room temperature?

Q 4.

What is the basicity of H3PO4?

Q 5.

List the important sources of sulphur.

Q 6.

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

Q 7.

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

Q 8.

 Discuss the general characteristics of Group 15 elements with reference to their electronic configuration, oxidation state, atomic size, ionisation enthalpy and electronegativity.

Q 9.

Discuss the general characteristics of Group 15 elements with reference to their electronic configuration, oxidation state, atomic size, ionisation enthalpy and electronegativity.

Q 10.

How is ammonia manufactured industrially?

Q 11.

 What happens when PCl5 is heated?

Q 12.

The HNH angle value is higher than HPH, H AsH and HSbH angles. Why?
(Hint: Can be explained on the basis of sp3 hybridisation in NH3 and only s-p bonding , between hydrogen and other elements of the group).

Q 13.

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

Q 14.

 How is SO2 an air pollutant?

Q 15.

 How are XeOand XeOF4prepared?

Q 16.

 Arrange the following in the order of property indicated for each set: –
(i) F2 , Cl2 , Br2 , I2 – increasing bond dissociation enthalpy.
(ii) HF, HCI, HBr, HI – increasing acid . strength.
(iii) NH3, PH3, AsH3, SbH3, BiH3 – increasing Sol. base strength.

Q 17.

The HNH angle value is higher than HPH, H AsH and HSbH angles. Why?
(Hint: Can be explained on the basis of sp3 hybridisation in NH3 and only s-p bonding , between hydrogen and other elements of the group).

Q 18.

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

Q 19.

What are the oxidation states of phosphorus in  the following: –
(i) H3PO3 (ii)PCl3
(iii) Ca3P2(iv)Na3PO4
(v) POF3

Q 20.

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

Q 21.

Illustrate how copper metal can give different products on reaction with HN03.

Q 22.

 Describe the manufacture of H2SO4 by contact process?

Q 23.

Bond angle in PH4+ is higher than that in PH3. Why?

Q 24.

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

Q 25.

How are xenon fluorides XeF2, XeF4 and XeF6  obtained?

Q 26.

Why does O3 act as a powerful oxidising agent?

Q 27.

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

Q 28.

Why is dioxygen a gas but sulphur a solid?

Q 29.

Why are halogens coloured?

Q 30.

Write the reactions of F2 and Cl2 with water.

Q 31.

Why does O3 act as a powerful oxidising agent?

Q 32.

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

Q 33.

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 34.

PCl5 reacts with finely divided silver on heating and a white silver salt is obtained, which dissolves on adding excess aqueous NH3 solution. Write the reactions involved to explain what happens.

Q 35.

Mention the conditions required to maximise the yield of ammonia.

Q 36.

How does ammonia react with a solution of Cu2+?

Q 37.

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

Q 38.

Sea is the greatest source of some halogens. Comment.

Q 39.

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

Q 40.

How is ammonia manufactured industrially?

Q 41.

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

Q 42.

What happens when PCl5 is heated?

Q 43.

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

Q 44.

Why does the reactivity of nitrogen differ from phosphorus?

Q 45.

Give the disproportionation reaction of H3 P03 .

Q 46.

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

Q 47.

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 48.

Why are halogens coloured?

Q 49.

In qualitative analysis when H2S is passed through an aqueous solution of salt acidified with dil. HCl, a black precipitate is obtained. On boiling the precipitate with dil. HNO3, it forms a solution of blue colour. Addition of excess of aqueous solution of ammonia to this solution gives
ncert-exemplar-problems-class-12-chemistry-p-block-elements-3

Q 50.

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 ——-