P Block Elements

Question 1

The main use of dinitrogen is in the manufacture of ammonia and other industrial chemicals containing nitrogen eg

Answer 1

calcium cyanamide

Question 2

Statement 1: Nitrogen also finds use where an inert atmosphere is required (e.g., in iron and steel industry, inert diluent for reactive chemicals).
Statement 2: Liquid dinitrogen is used as a refrigerant to preserve biological materials, food items and in cryosurgery.

Answer 2

Both statements are true

Question 3

Assertion: NO2 forms a dimer structure
Reason: NO2 contains odd number of valence electrons. It behaves as a typical odd molecule. On dimerisation, it is converted to stable N2O4 molecule with even number of electrons.

Answer 3

Both are true and correct explanation

Question 4

Statement 1: Laboratory grade nitric acid contains ~ 68% of the HNO3 by mass and has a specific gravity of 1.504.
Statement 2: The major use of nitric acid is in the manufacture of ammonium nitrate for fertilisers and other nitrates for use in explosives and pyrotechnics

Answer 4

Both are true

Question 5

Statement 1: Nitric acid is also used for the preparation of nitroglycerin, trinitrotoluene and other organic nitro compounds.
Statement 2: Other major uses are in the pickling of stainless steel, etching of metals and as an oxidiser in rocket fuels.

Answer 5

Both are true

Question 6

Statement 1: The spontaneous combustion of phosphine is technically used in Holme’s signals.
Statement 2: Containers containing calcium carbide and calcium phosphide are pierced and thrown in the sea when the gases evolved burn and serve as a signal. It is also used in smoke screens.

Answer 6

Both are true

Question 7

What happens when H3PO3 is heated?

Answer 7

orthophophorous acid (or phosphorous acid) on heating disproportionates to give orthophosphoric acid (or phosphoric acid) and phosphine.

4H3PO3———>3H3PO4. +. PH3

acids in +3 oxidation state of phosphorus tend to disproportionate to higher and lower oxidation states.

Question 8

Assertion: H2S is less acidic than H2Te. Why?
Reason: Due to the decrease in bond (E–H) dissociation enthalpy down the group, acidic character increases.

Answer 8

Both are correct and correct explanation

Question 9

Which form of sulphur shows paramagnetic behaviour?

Answer 9

In vapour state sulphur partly exists as S2 molecule which has two unpaired electrons in the antibonding π* orbitals like O2 and, hence, exhibits paramagnetism.

Question 10

Assertion: Although electron gain enthalpy of fluorine is less negative as compared to chlorine, fluorine is a stronger oxidising agent than chlorine.
Reason: It is due to
(i) low enthalpy of dissociation of F-F bond
(ii) high hydration enthalpy of F–

Answer 10

Both are true and correct explanation

Question 11

poisonous gases such as phosgene
tear gas
mustard gas

Answer 11

COCl2

CCl3NO2

ClCH2CH2SCH2CH2Cl

Question 12

Assertion: When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride.
Reason: Its reaction with iron produces H2.
Liberation of hydrogen prevents the formation of ferric chloride.

Answer 12

Both are correct and correct explanation

Question 13

Statement 1: Inter halogen compounds can be used as non aqueous solvents.
Statement 2: Interhalogen compounds are very useful fluorinating agents. ClF3 and BrF3 are used for the production of UF6 in the enrichment of 235U.

U(s) + 3ClF3(l) → UF6(g) + 3ClF(g)

Answer 13

Both are correct