Chemistry 12 Chapter 7 Exemplar Solutions the P Block Elements Part 4

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III. Short Answer Type

Question 38:

In the preparation of by Contact Process, why is not absorbed directly in water to form ?


Acid fog is formed, which is difficult to condense.

Question 39:

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


Question 40:

Write the structure of pyrophosphoric acid.


Pyrophosphoric acid

Pyrophosphoric Acid

Question 41:

forms bubbles when passed slowly in water but dissolves. Explain why?


forms hydrogen bonds with water therefore it is soluble in it but cannot form hydrogen bond with water so it escapes as gas.

Question 42:

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


[Hint: It has Trigonal bipyramidal geometry]

Question 43:

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


In gaseous state exists as monomer which has one unpaired electron but in solid state it dimerises to so no unpaired electron is left hence solid form is diamagnetic.

Question 44:

Give reason to explain why exists but does not exist.


Because fluorine is more electronegative as compared to chlorine.

Question 45:

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


Bond angle of is larger, because oxygen is more electronegative than sulphur therefore bond pair electron of bond will be closer to oxygen and there will be more bond-pair bond-pair repulsion between bond pairs of two bonds.

Question 46:

is known but is not. Why?


Due to small size of fluorine six can be accommodated around sulphur whereas chloride ion is comparatively larger in size, therefore, there will be interionic repulsion.

Question 47:

On reaction with , phosphorus forms two types of halides ‘A’ and ‘B’. Halide A is yellowish-white powder but halide ‘B’ is colourless oily liquid. Identify A and B and write the formulas of their hydrolysis products.


A is (It is yellowish white powder)

B is ((It is a colourless oily liquid)

Hydrolysis products are formed as follows:

Question 48:

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


(brown complex)

Question 49:

Explain why the stability of oxoacids of chlorine increases in the order given below:


Oxygen is more electronegative than chlorine, therefore dispersal of negative charge present on chlorine increases from to ion because number of oxygen atoms attached to chlorine is increasing. Therefore, stability of ions will increase in the order given below:

Thus due to increase in stability of conjugate base, acidic strength of corresponding acid increases in the following order

Question 50:

Explain why ozone is thermodynamically less stable than oxygen.


See the NCERT textbook for Class XII, page 186

Question 51:

reacts with water according to equation . Calculate the volume of solution required to neutralise the acid formed by dissolving of in .


(Neutralisation reaction

Product formed by of is neutralised by 8 mols of

∴ Product formed by mol of will be neutralised by mol of

Molarity of solution is

is present in solution

is present in of solution.

Question 52:

White phosphorus reacts with chlorine and the product hydrolyses in the presence of water. Calculate the mass of obtained by the hydrolysis of the product formed by the reaction of 62 g of white phosphorus with chlorine in the presence of water.


of white phosphorus produces of

62g of white phosphorus has been taken which is equivalent to .

Therefore will be formed.

Mass of

Developed by: