Chemistry 1 Marks Question

2.

Because Fluorine is the most electronegative element.

Due to its polymeric structure, red phosphorus is much less reactive than white phosphorus or white phosphorus is under strain.

3.

4.

Due to “inert pair effect” or because lower oxidation state becomes more stable for Bi than Sb.

Nitrogen has three unpaired electrons and one lone pair of electrons, therefore, it can form three covalent bonds and one coordinate bond.

In pentahalides, the oxidation state is +5 and in trihalides, the oxidation state is +3. Since the metal ion with a high charge has more polarizing power, pentahalides are more covalent than trihalides.

Due to the presence of a lone pair of electrons on the sulphur atom, sulphurous acid can be easily oxidised to sulphuric acid. Therefore, it acts as a reducing agent.

Acid fog is formed, which is difficult to condense.

Fluorine is the most electronegative element and cannot exhibit any positive oxidation state. Other halogens have d-orbitals and therefore, can expand their octets and show +1, +3, +5 and +7 oxidation states also.

Pt is a noble metal and does not react very easily. All other elements, Zn, Ti, Fe, are quite reactive. Hence, oxygen does not react with platinum (Pt) directly.

Both the S-O bonds are covalent and have equal strength due to resonating structures.

The elements present in Group 18 have their valence shell orbitals completely filled and, therefore, react with a few elements only under certain conditions. Therefore, they are known as noble gases.

In the order of increasing acid strength in water (i.e., aqueous solution) HI is strongest acid while HF is the weakest acid.
This is because as moving down the group size increase and hence weaken the bond as a result more availability of hydrogen.
H - F < H - Cl < H - Br < H - I

This is because fluorine is more electronegative than oxygen.

Chalcogens means ore forming. The elements of Group 16 are called chalcogens because many metals are found as oxides and sulphides and a few such as selenides and tellurides.

Both, nitrogen (N) and chlorine (Cl) have electronegativity of 3.0. However, only
nitrogen is involved in the hydrogen bonds (e.g., NH3) and not chlorine. This is due to smaller atomic size of nitrogen (atomic radius = 70 pm) as compared to chlorine (atomic radius = 99 pm), therefore, N can cause greater polarisation of N-H bond than Cl in case of CI-H bond.Consequently, N atom is involved in hydrogen bonding and not chlorine.

The halogens are strong oxidising agents due to low bond dissociation enthalpy, high electronegativity and large negative electron gain enthalpy.

As the size of the noble gas increases, van der Waals forces of attraction increase accordingly and hence the boiling points increase from He to Rn.

No, because F atom has no d-orbital and therefore it cannot expand its valance shell. Further, three big sized Cl atoms cannot be accommodated around a small F atom.

Due to extra stable half-filled p-orbitals electronic configurations of Group 15 elements, larger amount of energy is required to remove electrons compared to Group 16 elements.

The halogens are coloured because their molecules absorb light in the visible region. As a result of which their electrons get excited to higher energy levels while the remaining light is transmitted. The color of halogens is the color of this transmitted light.

Noble gases have only Van der Waals’ radii while others have covalent radii. As van der Waals’ radii are larger than covalent radii, hence, noble gases have comparatively large atomic sizes.

Helium is used as a diluent for oxygen in modern diving apparatus because of its very low solubility in blood.

This is because 1, 2 or 3 electrons from the 5p-orbitals can be excited to empty 5d-orbitals and thus making 2, 4 or 6 half-filled orbitals available for bond formation.

Atomic size increases from sulphur to polonium, therefore, tendency to gain two electrons decreases.

Orthophosphoric acid contains three O-H groups and hence undergoes extensive H-bonding.