Chemistry

The p-Block Elements.

Question:

On heating ammonium dichromate and barium azide separately we get
(a) N2 in both cases
(b) N2 with ammonium dichromate and NO with barium azide
(c) N2O  with ammonium dichromate and N2 with barium azide
(d) N2O with ammonium dichromate and N2O with barium azide

Answer:

(a)
ncert-exemplar-problems-class-12-chemistry-p-block-elements-12

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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.

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

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.

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

Q 5.

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

Q 6.

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 7.

 Write two uses of ClO2

Q 8.

Why are halogens strong oxidising agents?

Q 9.

Write the reactions of F2 and Cl2 with water.

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.

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

Q 12.

Give the reason for bleaching action of Cl2.

Q 13.

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

Q 14.

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

Q 15.

 Why do noble gases have comparatively large atomic size?

Q 16.

Why is N2 less reactive at room temperature?

Q 17.

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

Q 18.

List the important sources of sulphur.

Q 19.

Why does O3 act as a powerful oxidising agent?

Q 20.

How is O3 estimated quantitatively?

Q 21.

Discuss the trends in chemical reactivity of group 15 elements.

Q 22.

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

Q 23.

Give the resonating structures of N02 and N2O5.

Q 24.

Write two uses of ClO2

Q 25.

 What happens when PCl5 is heated?

Q 26.

 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 27.

Write the reactions of F2 and Cl2 with water.

Q 28.

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

Q 29.

 How are XeOand XeOF4prepared?

Q 30.

How is the presence of SO2 detected ?

Q 31.

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

Q 32.

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 33.

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

Q 34.

How does ammonia react with a solution of Cu2+?

Q 35.

Why is the reactivity of nitrogen different from that of phosphorus?

Q 36.

Give the resonating structures of N02 and N2O5.

Q 37.

 Describe the manufacture of H2SO4 by contact process?

Q 38.

 Why are halogens strong oxidising agents?

Q 39.

How are xenon fluorides XeF2, XeF4 and XeFobtained?

Q 40.

Why are pentahalides more covalent than trihalidcs ?

Q 41.

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

Q 42.

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

Q 43.

Why does nitrogen show catenation properties less than phosphorus?

Q 44.

Describe the manufacture of H2SO4 by contact process?

Q 45.

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

Q 46.

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 47.

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 48.

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 ——-

Q 49.

Which of the following statements are correct?
(a) S – S bond is present in H2S2O6.
(b) In peroxosulphuric acid (H2SO5) sulphur is in +6 oxidation state.
(c) Iron powder along with Al2O3 and K2O is used as a catalyst in the preparation of NH3 by Haber's process
(d) Change in enthalpy is positive for the preparation of SO3 by catalytic oxidation of SO2.

Q 50.

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