Chemistry 2 Marks Questions

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1. Due to sterically protected sulphur atom.
2. Because Xe is with the lowest ionization enthalpy among the rest (except Rn which is radioactive).

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1. This is due to the ability of oxygen to form multiple bonds to metals.
2. This is because the energy required for the promotion of electrons inXenon is very high./Energy factor does not favour VB approach.

White phosphorus is more reactive due to its discrete tetrahedral structure and angular strain.

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1. Cryolite lowers the melting point of alumina. Or Molten cryolite dissolves alumina.
2. Carbon monoxide forms a volatile complex with nickel which on heating de-composes to gives pure nickle.

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Fluorine and oxygen are the most electronegative elements and hence are very reactive. So, they form compounds with noble gases, particularly xenon.

Air contains a large amount of nitrogen and the solubility of gases in liquids increases with increase in pressure. When sea divers dive deep into the sea, large amount of nitrogen dissolves in their blood. When they come back to the surface, solubility of nitrogen decreases and it separates from the blood and forms small air bubbles. This leads to a dangerous medical condition called bends. Therefore, air in oxygen cylinders used for diving is diluted with helium gas. This is done as He is sparingly less soluble in blood.

Noble gas are stable so they cannot form molecules In case noble gas from molecule the force of attraction that acting is vander waal force.
On other hand, other element form covalent bond and it is well known that vander waal radii is larger than covalent radii. Thus noble gases have comparatively large atomic sizes.

As we move from S to Se, the atomic size increases and hence the strength of E-E bond decreases. Thus, S-S bond is much stronger than Se-Se bond. Consequently, S shows greater tendency for catenation than selenium.

1. Oxidation state: Fluorine shows oxidation state of – 1 only. It does not show any positive oxidation state. Other halogens show oxidation states such as +1, +3, +5, +7 also.
2. Extra-ordinary reactivity: Fluorine is extraordinary most reactive element. This is due to F—F bond energy is very low as compared to that of other halogen molecules.

The oxidation state of Cl in perchloric acid is +7 while that of S in sulphuric acid is +6. Greater the oxidation state of central atom, more readily the O-H bond breaks and hence stronger is the acid.

Freons or chlorofluorocarbons (CFCs) are aerosols that accelerate the depletion of ozone. In the presence of ultraviolet radiations, molecules of CFCs break down to form chlorine-free radicals that combine with ozone to form oxygen.

Neon lights are visible from long distances even in fog and mist and hence neon is generally used for warning signals.

Catenation is much more common in phosphorous compounds than in nitrogen compounds. This is because of the relative weakness of the N-N single bond as compared to the P-P single bond. Since nitrogen atom is smaller, there is greater repulsion of electron density of two nitrogen atoms, thereby weakening the N-N single bond.

Passivity is attained by formation of a thin film of oxide on iron.

Neon and argon is inert gas because they are more stable than other.Uses of Neon:

1. Neon is mainly used in fluorescent lamps of tubes for advertising purposes. These are known as neon signs and can be seen at long distances even when there is a fog. Neon actually produces an orange red glow in the tube and on mixing with the vapours of other gases, glows or signs of different colours can be obtained.
2. It is used in filling sodium vapour lamps.
3. It is used in safety devices for protecting certain electrical instruments (voltmeters, relays, rectifiers etc.)

Uses of Argon:

1. It is used in metal filament electric lamps since it increases the life of the tungsten filament by retarding its vapourisation.
2. A mixture of argon and mercury vapours is used in fluorescent tubes.
3. It is used to create an inert atmosphere for welding and for carrying certain chemical reactions.

NO has an odd number of electrons (11 valence electrons) and hence is paramagnetic in the gaseous state. But in liquid and solid states, it exists as a symmetrical or asymmetrical dimer and hence is diamagnetic in these states.