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Advanced MCQs :
Which of the following molecules includes nitrogen atom having oxidation state equal to –2?
a) N2
b) NH2OH
c) N2H 4
d) NH3
N 2 O 4 ΔH = negative. The condition at which the conversion of NO
Given that 2NO 2 2
to N2O4 becomes more and more are :
a) lower temperature and lower pressure
b) lower temperature and higher pressure
c) higher temperature and higher pressure
d) higher temperature and lower pressure
Which of the following statements regarding nitrogen molecule is not correct?
a) Amongst the homonuclear diatomic molecules of second period, the bond dissociation
enthalpy is maximum in case of N2 molecule.
b) Amongst the homonuclear diatomic molecules of second period, the bond length is minimum
in case of N2 molecule.
c) Nitrogen molecule is paramagnetic in nature.
d) Only at high temperatures, nitrogen molecule reacts with metals and non metals forming
ionic and covalent nitrides.
Concept Explanation :
(a) General introduction :
1. Occurrence : First four elements are called as ‘chalcogens’ i.e. ore forming elements.
Oxygen : (1) Oxygen is the most abundant of all the elements on the earth. Oxygen
forms about 46.6% by mass of earth crust.
(2) Dry air contains 21.0% of oxygen by volume.
Sulphur : (1) Sulphur occurs less abundantly. It is only 0.03-0.1%.
(2) Sulphur in the combined form exists mainly as sulphates, gypsum
CaSO4.2H2O, epsum salt MgSO4, 7H2O, baryte BaSO4 and sulphides
like zinc blende ZnS, galena PbS, copper pyrities CuFeS2.
(3) It is found that very small quantity occurs as H2S (Hydrogen sulphide)
in volcanoes, hot springs, in meteorites, etc.
(4) Onion, garlic, mustard, eggs, proteins, hair and wool, the organic materials
also contain sulphur.
Selenium and tellurium occur as metal selenides and tellurides in sulphide ores.
Polonium is radioactive.
Group 16 consists of oxygen (O), sulphur (S), selenium (Se), tellurium (Te) and polonium
Chapter - 7 p – Block Elements
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