Chapter 4 Chemistry XII

Question 4.1: How does nitrogen differ from other elements of its groups?

Answer: Main differences of Nitrogen from other elements of its group are given below

Nitrogen is gas while other elements of its group are solid
Nitrogen forms diatomic molecule while other members from tight atomic molecule
Nitrogen does not show allotropy but other elements show allotrops.
Nitrogen forms multiple bonds while other elements do not form but compound.
Nitrogen does not form complex while other elements form complexes due to the available d- orbitals.

Question 4.2:Why does Aqua regia dissolve gold and Platinum?

Answer: A mixture of concentrated nitric acid(1 part by volume) and concentrated HCL (three part by volume) is called aquaria it is used to dissolve gold and Platinum.
3HCL + HNO3 -- >NOCl + Cl2 + 2H2O

2NOCl -->2NO + Cl2

Diu to liberated chlorine gold and Platinum are converted into there is water soluble salt.

2Au+ 3Cl2 -- >2AuCl3

Question 4.3: Why the element of group vi a other than oxygen show more than 2 oxidation States.

Answer: Except oxygen other members of group VIA show variable valences. For example, SCL2, SCL4 and SCL6. The + 2 oxidation state of S is shown due to 2 electrons in P orbitals. The + 4 oxidation state is shown when 2 electrons from p-orbitals are promoted to the next d-orbital. The +6 is shown when one electron is excited to next d-orbital.

Question 4.4: Write down a comparison of properties of oxygen and sulphur?

Answer:

Similarities

Both sulphur and oxygen are non metals.
Both oxygen and sulphur has same valence shell electron configuration of ns2, nP4.
Both oxygen and sulphur show allotropy.
Both are usually divalent.
Both form atomic molecule
Both are found in free and combined states.
Both combined with metals in the form of divalent anion
Both combined with non metals and form covalent compounds

Dissimilariteis

Oxygen is gas but sulphur is a solid at ordinary temperature.
Oxygen has two allotrops and but sulphur has 3 allotrops( alpha, beta and gamma farms)
Oxygen is a paramagnetic but sulphur is diamagnetic
Oxygen helps in combustion but sulphur is itself combustible
Oxygen is sparingly soluble in water but sulphur is insoluble in water.
Oxygen does not react with water water sulphur reacts with steam on very small scale 2H2O + 3 - > 2 H2S + SO2

Oxygen does not react with acid but sulphur reacts with concentrated nitric acid and concentrated sulphuric acid.
Oxygen does not react with alkalies while sulphur reacts with alkalis to farm sulphide and thiosulphate.
Oxygen shows Oxidation state of -2 but sulphur shows of state of -2 + 2 + 4 + 6.

Question 4.5: What is is meant by fuming nitric acid

Answer: Concentrated nitric acid saturated by nitrogen peroxide (NO2) is called fuming nitric acid it is prepared by bubbling and CO2 gas through concentrated nitric acid it is more powerful oxidising agent than concentrated nitric acid.

Question 4.6: Give the advantage of contact process for manufacture of sulphuric acid?Answer: Using contact process,

H2SO4 of any desired concentration can prepared.
H2SO4 produced has a very high degree of purity.
H2SO4 produced can be used for analytical purpose and for preparation of chemical explosive and medicine.

Question 4.7:Why is SO3 is dissolved in H2SO4 and not in water?
Answer: S3 is completely soluble in 98% sulphuric acid turn gives oleum. Then oleum is diluted with water to get H2SO4 of any desired concentration. On the hand, when SO3 is dissolved in water, then acid mist is formed. It is the reason that SO3 is dissolved in H2SO4 not I hot water

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