Chemistry

The p-Block Elements.

Question:

 How is SO2 an air pollutant?

Answer:

(1) SOdissolves in moisture present in air to form H2SO4 which damages building materials especially marble (acid – rain).- CaCO3 + H2SO3 ——->CaSO3 + H20 + CO2
(2)It corrodes metals like Fe and steel. It also brings about fading and deterioration of fabrics, leather, paper, etc., and affecting the colour of paints.
(3)Even in low concentration (= 0.03 ppm), it has damaging effect on the plants. If exposed for a long time, i.e., a few days or weeks, it slows down the formation of chlorophyll i. e., loss of green colour. This is called chlorosis.
(4)It is strongly irritating to the respiratory track. It cause throat and eye irritation, resulting into cough, tears and redness in eyes. It also cause breathlessness and effects larynx i. e. „ voice box.

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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.

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

Q 5.

Discuss the trends in chemical reactivity of group 15 elements.

Q 6.

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

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.

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 13.

Explain why fluorine forms only one oxoacid, HOF.

Q 14.

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

Q 15.

What happens when H3PO4 is heated?

Q 16.

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 17.

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

Q 18.

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

Q 19.

Write the structure of pyrophosphoric acid.

Q 20.

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

Q 21.

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

Q 22.

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

Q 23.

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

Q 24.

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

Q 25.

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

Q 26.

Why is dioxygen a gas but sulphur a solid?

Q 27.

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

Q 28.

Give the resonating structures of N02 and N2O5.

Q 29.

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

Q 30.

Why does nitrogen show catenation properties less than phosphorus?

Q 31.

Why are halogens strong oxidising agents?

Q 32.

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 33.

PH3 forms bubbles when passed slowly in water but NH3 dissolves. Explain.

Q 34.

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 35.

 What is the covalence of nitrogen in N2O5 ?

Q 36.

 What happens when PCl5 is heated?

Q 37.

What is the basicity of H3PO4?

Q 38.

 List the important sources of sulphur.

Q 39.

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

Q 40.

Give two examples to show the anomalous behaviour of fluorine.

Q 41.

Discuss the trends in chemical reactivity of group 15 elements.

Q 42.

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

Q 43.

Give the resonating structures of N02 and N2O5.

Q 44.

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

Q 45.

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

Q 46.

Which aerosols deplete ozone?

Q 47.

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

Q 48.

 How are XeOand XeOF4prepared?

Q 49.

 Why do noble gases have comparatively large atomic size?

Q 50.

 List the uses of neoirand argon gases.