Class 11th

Carbon monoxide (CO), sulphur dioxide (SO₂) and oxides of nitrogen (NO₂).

Mixing of soil or rock particles in water is called siltation.

Green chemistry can be applied as mentioned in the following examples:

(i) In dry-cleaning, use of liquefied CO₂ in place of tetrachloroethene.

(ii) In bleaching of paper using hydrogen peroxide instead of chlorine.

(iii) In the manufacture of chemicals like ethanal using environment-friendly chemicals and conditions.

PCBs are polychlorinated biphenyls. They are contaminants of water. They are used as fluids in transformers and capacitors

Organic pollutants in water

3.53. They have filled s-orbitals and hence do not tend to accept an additional electron. That is why energy is needed if an extra electron is to be added. Therefore, the electron gain enthalpies of Be and Mg are positive.

(a) warm, dry and sunny climate.

3.52. Ionization enthalpy represents the energy required to remove an electron from an isolated gaseous atom in its ground state. Nitrogen has a greater ionization enthalpy than that of oxygen due to its exactly half-filled p-orbitals.

(d) Chlorofluorocarbons (CFCs) are man-made industrial chemicals used in air conditioning etc.