Chemistry

The p-Block Elements.

Question:

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.

Answer:

(b) Both statements are correct but are independent of each other.

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The p-Block Elements.

Q 1.

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

Q 2.

 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 3.

Which of the following statements are true?
(a) Only type of interactions between particles of noble gases are due to weak dispersion forces.
(b) Ionisation enthalpy of.molecular oxygen is very close to that of xenon.
(c) Hydrolysis of XeF6 is a redox reaction.
(d) Xenon fluorides are not reactive.

Q 4.

 Why do noble gases have comparatively large atomic size?

Q 5.

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

Q 6.

 Write two uses of ClO2

Q 7.

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

Q 8.

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

Q 9.

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

Q 10.

In PCl5, phosphorus is in sp3d hybridised state but all its five bonds are not equivalent. Justify your answer with reason.

Q 11.

In the ring test of NO3 ion.Fe2+ion reduces nitrate ion to nitric oxide, which combines with Fe2+  (aq.) ion to form brown complex. Write the reactions involved in the formation of brown ring.

Q 12.

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

Q 13.

How is O3 estimated quantitatively?

Q 14.

Discuss the trends in chemical reactivity of group 15 elements.

Q 15.

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

Q 16.

Give the resonating structures of N02 and N2O5.

Q 17.

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

Q 18.

Why are halogens strong oxidising agents?

Q 19.

Write two uses of ClO2

Q 20.

Write the reactions of F2 and Cl2 with water.

Q 21.

SF6 is known but SCl6 is not. Why?

Q 22.

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

Q 23.

On heating compound (A) gives a gas (B) which is a constituent of air. This gas when treated with 3 mol of hydrogen (H2   ) in the presence of a catalyst gives another gas (C) which is basic in nature. Gas C on further oxidation in moist condition gives a compound (D) which is a part of acid rain. Identify compounds (A) to (D) and also give necessary equations of all the steps involved. –

Q 24.

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

Q 25.

How does ammonia react with a solution of Cu2+?

Q 26.

 What happens when PCl5 is heated?

Q 27.

Give the reason for bleaching action of Cl2.

Q 28.

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

Q 29.

 Knowing the electron gain enthalpy values of O—>O and O—>O2- as -141 and 702 kJ mol-1 respectively, how can you account for the formation of a large number of oxides having O2- species and not O?

Q 30.

Which aerosols deplete ozone?

Q 31.

 Describe the manufacture of H2SO4 by contact process?

Q 32.

 Why are halogens strong oxidising agents?

Q 33.

Write the reactions of F2 and Cl2 with water.

Q 34.

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

Q 35.

 How are XeOand XeOF4prepared?

Q 36.

Why are pentahalides more covalent than trihalidcs ?

Q 37.

Why is N2 less reactive at room temperature?

Q 38.

How does ammonia react with a solution of Cu2+?

Q 39.

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

Q 40.

List the important sources of sulphur.

Q 41.

Why does O3 act as a powerful oxidising agent?

Q 42.

How is the presence of SO2 detected ?

Q 43.

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

Q 44.

Why does nitrogen show catenation properties less than phosphorus?

Q 45.

On addition of cone. H2SO4 to a chloride salt, colourless fumes are evolved but in case of iodide salt, violet fumes come out. This is because
ncert-exemplar-problems-class-12-chemistry-p-block-elements-1

Q 46.

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 47.

In which of the following reactions cone. H2S04 is used as an oxidizing reagent?
ncert-exemplar-problems-class-12-chemistry-p-block-elements-25

Q 48.

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

Q 49.

Give reason to explain why ClF3 exists but FCl3 does not exist.

Q 50.

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