Chemistry

The p-Block Elements.

Question:

List the uses of neoirand argon gases.

Answer:

Uses of Neon Neon is used in discharge tubes and fluorescent bulbs for advertisement display purposes. Glow’of different colours neon signs' can be produced by mixing neon with other gases. Neon bulbs and used in botanical gardens and in green' houses.
Uses of Argon Argon is used mainly to provide an inert atmosphere in high temperature metallurgical processes such as arc welding of metals and alloys. In the laboratory, it is used for handling substance which are air sensitive.
It is used in filling incandescent and fluorescent lamps where its presence retards the sublimation of the filament and thus increases the life of the lamp.It is also used in "neon signs"for obtaining lights of different colours.

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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.

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

Q 5.

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

Q 6.

Discuss the trends in chemical reactivity of group 15 elements.

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.

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

Q 48.

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

Q 49.

Which aerosols deplete ozone?

Q 50.

 How are XeOand XeOF4prepared?