Chemistry

The p-Block Elements.

Question:

What is the basicity of H3PO4?

Answer:

ncert-solutions-for-class-12-chemistry-the-p-block-elements-7

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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.

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

Q 4.

Give the resonating structures of N02 and N2O5.

Q 5.

Why are halogens strong oxidising agents?

Q 6.

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 7.

Match the formulas of oxides given in Column I with the type of oxide given in Column II and mark the correct option.
ncert-exemplar-problems-class-12-chemistry-p-block-elements-47

Q 8.

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

Q 9.

How is the presence of SO2 detected ?

Q 10.

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

Q 11.

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

Q 12.

Write two uses of ClO2

Q 13.

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

Q 14.

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 15.

 Why is N2 less reactive at room temperature?

Q 16.

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

Q 17.

Give the reason for bleaching action of Cl2.

Q 18.

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

Q 19.

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

Q 20.

How are xenon fluorides XeF2, XeF4 and XeFobtained?

Q 21.

Why is N2 less reactive at room temperature?

Q 22.

How is O3 estimated quantitatively?

Q 23.

Which of the following acid forms three series of salts?
(a) H2PO2  (b) H3BO3 (C)H3PO4(d)H3PO3

Q 24.

How does ammonia react with a solution of Cu2+?

Q 25.

Name two poisonous gases which can be prepared from chlorine gas

Q 26.

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

Q 27.

Which aerosols deplete ozone?

Q 28.

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

Q 29.

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

Q 30.

Describe the manufacture of H2SO4 by contact process?

Q 31.

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

Q 32.

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 33.

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 34.

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

Q 35.

Give two examples to show the anomalous behaviour of fluorine.

Q 36.

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

Q 37.

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

Q 38.

What are the oxidation states of phosphorus in  the following: –
(i) H3PO3 (ii)PCl3
(iii) Ca3P2(iv)Na3PO4
(v) POF3

Q 39.

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 40.

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 41.

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

Q 42.

Give the resonating structures of N02 and N2O5.

Q 43.

Why is dioxygen a gas but sulphur a solid?

Q 44.

 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 45.

Why does O3 act as a powerful oxidising agent?

Q 46.

Comment on the nature of two S-O bonds formed in S02 molecule. Are the two S-O bonds in this molecule equal ?

Q 47.

Mention three areas in which H2SO4 plays an important role.

Q 48.

Why does NH3 form hydrogen bond but PH3 does not?

Q 49.

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

Q 50.

The HNH angle value is higher than HPH, H AsH and HSbH angles. Why?
(Hint: Can be explained on the basis of sp3 hybridisation in NH3 and only s-p bonding , between hydrogen and other elements of the group).