Chemistry

The p-Block Elements.

Question:

What happens when H3PO4 is heated?

Answer:

On heating, H3PO3  disproportionates to form PH3 and H3PO4 with O.S. of-3and + 5.
ncert-solutions-for-class-12-chemistry-the-p-block-elements-8

previuos
next

The p-Block Elements.

Q 1.

 Which one of the following does not exist ?
(i)XeOF4 (ii)NeF2
(iii)XeF4 (iv)XeF6

Q 2.

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

What is the basicity of H3PO4?

Q 6.

Why does O3 act as a powerful oxidising agent?

Q 7.

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

Q 8.

Why is dioxygen a gas but sulphur a solid?

Q 9.

How is ammonia manufactured industrially?

Q 10.

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 [he formation of a large number of oxides having O2- species and not O?

Q 11.

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

Q 12.

Write two uses of ClO2

Q 13.

How are XeO3  and XeOF4prepared?

Q 14.

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 15.

Write the structure of pyrophosphoric acid.

Q 16.

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

Q 17.

Why is ICI more reactive than l2?

Q 18.

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

Q 19.

How can-you prepare Cl2 from HCl and HCl from CI2? Write reactions only.

Q 20.

Which one of the following does not exist ?
(i)XeOF4 (ii)NeF2
(iii)XeF4 (iv)XeF6

Q 21.

On heating with concentrated NaOH solution in an inert atmosphere of CO2, white phosphorus gives a gas. Which of the following statement is incorrect about the gas?
(a) It is highly poisonous and has smell like rotten fish.
(b) Its solution in water decomposes in the presence of light.
(c) It is more basic than NH3  
(d) It is less basic than NH3

Q 22.

Which of the following options are not in accordance with the properly mentioned against them?
ncert-exemplar-problems-class-12-chemistry-p-block-elements-20

Q 23.

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 24.

Which of the following statements are correct for SO2  gas?
(a) It acts as a bleaching agent in moist conditions.
(b) Its molecule has a linear geometry.
(c) Its dilute solution is used as disinfectant.
(d) It can be prepared by the reaction of dilute H2SO4 with metal sulphide.

Q 25.

Why is nitric oxide paramagnetic in gaseous state but the solid obtained on cooling is diamagnetic?

Q 26.

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 27.

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 28.

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 29.

How does ammonia react with a solution of Cu2+?

Q 30.

 What is the covalence of nitrogen in N2O5 ?

Q 31.

Why is bond angle in PH+4 ion higher than in PH3 ? (Pb. Board 2009)

Q 32.

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

Q 33.

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

Q 34.

Why does NH3 form hydrogen bond but PH3 does not?

Q 35.

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

Q 36.

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

Q 37.

 Why are halogens strong oxidising agents?

Q 38.

 Why do noble gases have comparatively large atomic size?

Q 39.

Why is H2O a liquid and H2S a gas ?

Q 40.

Mention three areas in which H2SO4 plays an important role.

Q 41.

Discuss the trends in chemical reactivity of group 15 elements.

Q 42.

Why does NH3 form hydrogen bond but PH3 does not?

Q 43.

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

Q 44.

Which aerosols deplete ozone?

Q 45.

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 46.

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

Q 47.

List the uses of neoirand argon gases.

Q 48.

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 49.

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 50.

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