Ncert Solutions Chemistry Class 11th

This is mainly due to the large number of industries and power plants in the nearby areas. Acid rain has vapours of sulphuric acid dissolved in it. When it comes in contact with various statues or monuments, the acid reacts chemically with marble (calcium carbonate).
CaCO₃ + H₂SO₄ à CaSO₄ + H₂O + CO₂

As a result, the monument is being slowly disfigured, and the marble is getting discoloured and lustreless.

3.26. 

CO₂ is mainly responsible for the greenhouse effect. Other greenhouse gases are methane, nitrous oxide, water vapours, CFCs (chlorofluorocarbons) and Ozone.

Tropospheric pollution occurs due to the presence of undesirable solid or gaseous particles in the air. The following are the major gaseous and particulate pollutants present in the troposphere:

1. Gaseous air pollutants: These are oxides of sulphur, nitrogen and carbon, hydrogen sulphide, hydrocarbons, ozone and other oxidants.

2. Particulate pollutants: These are dust, mist, fumes, smoke, smog etc.

3.25. Isotopes have same number of electrons and protons, only the number of neutrons is different. The atomic number remains the same and only atomic mass differs. Hence the ionization energy of the isotopes of a chemical element remains the same.

Environmental chemistry is a branch of environmental studies. Environmental studies deal with the sum of all social, economical, biological, physical and chemical interrelations with our surroundings. Environmental chemistry deals with the study of the origin, transport, reactions, effects and fates of chemical species in the environment

3.24.  (a) Gain of an electron leads to the formation of an anion. The size of an anion will be larger than that of the parent atom because the addition of one or more electrons would result in increased repulsion among electrons and decrease in effective nuclear charge.

(b) Loss of an electron from an atom results in the formation of a cation. A cation is smaller than its parent atom because it has former electrons while its nuclear charge remains the same.

3.23. On Pauling scale, the electronegativity of nitrogen is 3.0 which indicates that it is quite electronegative. But it is not correct to say that the electronegativity of nitrogen in all the compounds is 3. It varies with the atoms that N is bonded with. For example, in NH₃, N has a different electronegativity than N in NO₂

3.22. Electron gain enthalpy refers to tendency of an isolated gaseous atom to accept an additional electron to form a negative ion. Whereas electronegativity refers to tendency of the atom of an element to attract shared pair of electrons towards it in a covalent bond.