Question Pool The p-Block Elements

The p-Block Elements - SAMAGRA Question Pool & Answers | Class 12

Kerala Syllabus SAMAGRA SCERT SAMAGRA Question Pool for Class 12 Chemistry The p-Block Elements

Qn 1.

Which is the element present in group 15 of periodic table showing oxidation state from -3 to +5?

Answer)

Nitrogen
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Qn 2.

How ammonia is prepared in laboratory? What is the chemical change happening when ammonium hydroxide solution is added drop wise to excess into a copper sulphate solution? (Give equations wherever necessary.)

Answer)

Ammonia is prepared in laboratory by treating ammonium salts with caustic soda or calcium hydroxide. 2NH₄Cl + Ca(OH)₂ → 2NH₃ +
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Qn 3.

phosphorous is the second element in the 15 th group of the periodic table.

Which are the two important halides of phosphorous?
How they are prepared?
Explain with equations, their action with moisture.

Answer)
1. PCl₃ and PCl₅.
2. PCl₃ is obtained by passing dry chlorine over heated white
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Qn 4.

How ozone is prepared? Give any two oxidizing reactions of ozone.

Answer)

Ozone is prepared by passing a slow dry stream of oxygen through a silent electrical discharge.

3O₂ →
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Qn 5.

The most important oxoacid of nitrogen is Nitric acid.

Name the other two oxoacids of nitrogen.
With the help of balanced chemical equations, explain the reaction of Cu with dilute and concentrated nitric acids.

Answer)
1. Hyponitrous acid(H₂N₂O₂) and Nitrous acid ( HNO₂)
2. 3Cu + 8 HNO_3(dilute)
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Qn 6.

Heating white phosphorous with concentrated NaOH in an inert atmosphere of CO₂ gives a compound used in Holme’s signals. Name the compound. Write the balanced equation showing the reaction.

Answer)
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Qn 7.

An oxide of nitrogen which is brown in color and paramagnetic, on cooling becomes another oxide which is diamagnetic liquid or solid. Identify the two oxides and write the equation showing the change.

Answer)
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Qn 8.

Why the first element in groups 15, 16, 17 and 18 of the periodic table show abnormal properties compared to rest of the members?

Answer)

This is due to the small size, high electronegativity, high ionization enthalpy and non-availability of d
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Qn 9.

Which inter halogen compound is used in the production of UF₆ , a compound that is used in the enrichment of U²³⁵.

Answer)

ClF₃
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Qn 10.

Deacon’s process is used for the manufacture of ------------ .

Answer)

Chlorine
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Qn 11.

Name the process used for the large scale preparation of Nitric acid.

Answer)

Ostwald’s process
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Qn 12.

Name the compound of phosphorus which is used in Holme’s signal.

Answer)

Phosphine
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Qn 13.

The compound of 15^th group element which is used as a refrigerant is------ .

Answer)

Ammonia
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Qn 14.

The strongest hydrohalic acid is -----------

Answer)

Hydriodic acid
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Qn 15.

Name the important oxoacids of nitrogen and write their chemical formulae.

Answer)

1. Nitrous acid : HNO₂

2. Nitric acid : HNO₃

3. Hyponitrous acid :
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Qn 16.

Nitrogen does not form pentahalides. Why?

Answer)

Nitrogen has no vacant d-orbital
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Qn 17.

Why dintrogen (N₂ ) is inert at room temperatuer?

Answer)

Due to high bond dissociation enthalpy of N-N triple
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Qn 18.

Expain the manufacture of ammonia?

Answer)

Ammonia is manufactured by Haber's process.In this nitrogen gas is mixed with hydrogen gas. High Pressure and low temperature favours the formation of ammonia .
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Qn 19.

Write a method to prepare very pure nitrogen (N₂) in the laboratory

Answer)

By the thermal decomposition of Barium azide or sodium azide

Ba( N₃ )₂ → Ba + 3
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Qn 20.

Thermal stability of hydrides of group 15 elements decreases from NH₃ to BiH₃ . Why ?

Answer)

Down the group from N to Bi atomic size increases and bond dissociation enthalpy of M-H bond decreases.Hence thermal stability
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Qn 21.

Write three anomolous properties of nitrogen compared to other elements of group 15

Answer)

1. Nitrogen can form stable p pi - p pi multiple bonds

2. Nitrogen is diatomic gas while others are polyatomic solids

3. Catenation tendancy in
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Qn 22.

In group 15 stability of +5 oxidation state decreases down the group. Give reason

Answer)

It is due to Inert pair effect. Inert pair effect increases down the group and +3 oxidation state becomes more stable down the
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Qn 23.

In group 15 stability of +5 oxidation state decreases down the group. Give reason

Answer)

It is due to Inert pair effect. Inert pair effect increases down the group and +3 oxidation state becomes more stable down the
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Qn 24.

First ionisation enthalpy of Nitrogen is higher than Oxygen. Why?

Answer)

due to the stable outer ns²np³ electronic configuration.of nitrogen , s level is fully filled and p level is exactly half
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Qn 25.

Which allotropic form of phosphorous is more reactive?

Answer)

White phosphorus
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Qn 26.

What are the products obtained by the thermal decomposition of sodium azide.

Answer)

Thermal decomposition of sodium azide gives dinitrogen gas and metallic sodium
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