Chemistry

The necessary conditions for a molecule to be aromatic are:

• It should have a single cyclic cloud of delocalised n-electrons above and below the plane of the molecule.
• It should be planar. This is because complete delocalization of n-electrons is possible only if the ring is planar to allow cyclic overlap of p-orbitals.
• It should contain Huckel number of electrons, i.e., (4n + 2) n-electrons where n = 0, 1, 2, 3 etc.
  A molecule which does not satisfy any one or more of the above conditions is said to be non-aromatic.

Benzene is a resonance hybrid of two canonical forms. In the resonance hybrid, all the six pi electrons are completely delocalized. This results in resonance stabilization.

1.45 For fcc unit cell, a=2√2?.

Here, a is the edge length and r is the atomic radius (0.144 nm).

a = 2√2 *0.144 = 0.407 nm

Hence, the length of a side of a cell is 0.407 nm.

The structures of cis- and trans-isomer of hex-2-ene are:

The boiling point of a molecule depends upon dipole-dipole interactions. Since cis-isomer has higher dipole moment, therefore, it has higher boiling point.

3.40. Within a period, the oxidising character increases from left to right. Therefore, among F, O and N, oxidising power decreases in the order: F > O > N. However, within a group, oxidising power decreases from top to bottom. Thus, F is a stronger oxidising agent than Cl. Further because O is more electronegative than Cl, therefore, O is a stronger oxidising agent than Cl. Thus, overall decreasing order of oxidising power is: F > O > Cl > N, i.e., option (b) is correct.

A combustion reaction is a reaction in which a substance reacts with oxygen gas, there is a formation of carbon dioxide, water with the evolution of light and heat.

(i) 2C₄H₁₀ (g) +13 O₂ (g)?8CO₂ (g)+10H₂O (g) + Heat

(ii) 2C₅H₁₀ (g) +15 O₂ (g)?10CO₂ (g)+10H₂O (g) + Heat

(iii) 2C₆H₁₀ (g) +17 O₂ (g)?12CO₂ (g)+10H₂O (g) + Heat

The ozonolysis of 4-Ethylhex-3-ene gives propanal and pentan-3-one.
The structural formula of the alkene (4-Ethylhex-3-ene) is as shown.

(i) Write the structures of propanal and pentan-3-ene with their oxygen atoms facing each other, we have,

 

(ii) Remove oxygen atoms and join the two fragments by a double bond, the structure of the alkene is

1.44 Ge is group 14 element and In is group 13 element. Hence an electron deficient hole is created and therefore, it is p–type.
2. B is group 13 elements and Si is group 14 elements, there will be a free electron. Hence, it is n-type

3.39. In a period, the non-metallic character increases from left to right. Thus, among B, C, N and F, non-metallic character decreases in the order: F > N > C > B. However, within a group, non-metallic character decreases from top to bottom. Thus, C is more non-metallic than Si. Therefore, the correct sequence of decreasing non-metallic character is: F > N > C > B > Si, i.e., option (c) is correct.

(i) An aldehyde with molar mass of 44 u is ethanal, CH₃CH=0

(ii) Write two moles of ethanal side by side with their oxygen atoms pointing towards each other.

 

(iii) Remove the oxygen atoms and join them by a double bond, the structure of alkene 'A' is

As required, but-2-ene has three C—C, eight C—H a? bonds and one C—C? -bond.