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.

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

Q 4.

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

Q 5.

Discuss the trends in chemical reactivity of group 15 elements.

Q 6.

Why does nitrogen show catenation properties less than phosphorus?

Q 7.

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 8.

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

Q 9.

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

Q 10.

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 11.

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

Q 12.

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

Q 13.

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

Q 14.

Give two examples to show the anomalous behaviour of fluorine.

Q 15.

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

Q 16.

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

Q 17.

Explain why fluorine forms only one oxoacid, HOF.

Q 18.

 How are XeOand XeOF4prepared?

Q 19.

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

Q 20.

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

Q 21.

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

Q 22.

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

Q 23.

Explain why fluorine forms only one oxoacid, HOF.

Q 24.

Which of the following statements are correct?
(a) Among halogens, radius ratio between iodine and fluorine is maximum.
(b) Leaving F – F bond, all halogens have weaker X – X bond than X – X’ bond in interhalogens.
(c) Among interhalogen compounds maximum number of atoms ate present in iodine fluoride.
(d) Interhalogen compounds are more reactive than halogen compounds.

Q 25.

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

Q 26.

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 27.

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 28.

 Why is N2 less reactive at room temperature?

Q 29.

 What is the covalence of nitrogen in N2O5 ?

Q 30.

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

Q 31.

What is the basicity of H3PO4?

Q 32.

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

Q 33.

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

Q 34.

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 35.

Why is dioxygen a gas but sulphur a solid?

Q 36.

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

Q 37.

Why does the reactivity of nitrogen differ from phosphorus?

Q 38.

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

Q 39.

How are XeO3  and XeOF4prepared?

Q 40.

Give the formula and describe the structure of a noble gas species which is isostructural with:  (i) ICI4 (ii) IBr2 (iii) Br03

Q 41.

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 42.

Write the structure of pyrophosphoric acid.

Q 43.

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

Q 44.

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

Q 45.

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 46.

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 47.

Assertion (A): SF6 cannot be hydrolysed but SF4 can be.
Reason (R): Six F atoms in SF6 prevent the attack of H2O on sulphur atom of SF6.

Q 48.

 What happens when PCl5 is heated?

Q 49.

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

Q 50.

 List the important sources of sulphur.