Carbon hydrides of the type C_n H_{2n + 2} are electron precise hydrides. Because they have atom with exact number of electrons to form covalent bonds.
Thus, they do not behave as Lewis acid or base. Since they have no tendency to accept or lose electrons.

Alkenes are rich source of loosely held \(\pi \) electrons, due to which they show electrophilic addition reaction. Electrophilic addition reactions of alkenes are accompanied by large energy changes so these are energetically favourable than that of Electrophilic substitution reactions.
In special conditions alkenes also undergo free radical substitution reactions.
In arenes during electrophilic addition reactions aromatic character of benzene ring is destroyed while during electrophilic substitution reactions of areans are enegetically more favourable than that of electrophilic addition reaction.
That's why alkenes prefer to undergo electrophilic addition reaction while arenes prefer electrophilic substitution reactions.

When an aqueous solution of borax is acidified with HCl, boric acid is formed.
\(Na_{ 2 }\underset { Borax }{ B4 } O_{ 7 }+2HCl+5H_{ 2 }O\rightarrow 2NaCl+4H_{ 3 }\underset { Boric \ acid }{ BO_{ 3 } } \)
Boric acid is a white crystalline solid. It is soapy to touch because of its planar layered structure. Boric acid is a weak monobasic acid. It is not a protonic acid but acts as a Lewis acid by accepting electrons from a hydroxyl ion.
\(B(OH)_{ 3 }+2HOH\rightarrow [B(OH)_{ 4 }]^{ - }+H_{ 3 }O^{ + }\)

Hydrogen is a gas at room temperature. Because of it occupying large volume, it is difficult to transport it either by rail or by road. However, by cooling and applying high pressure, gaseous \({ H }_{ 2 }\) can be converted into liquid \({ H }_{ 2 }\)which has much smaller volume and hence, can be transported easily. Thus, the basic property of hydrogen which is useful for hydrogen economy is that it can be converted into a liquid by cooling under high pressure.

When compression is carried out in infinite steps with change in pressure, it is a reversible process. Work done on the gas is represented by the shaded area.

The energy which arises due to motion of atoms or molecules in a body is known as thermal energy.It is a measure of average kinetic energy of the particles.It increases with increases with increase in temperature.

Nuclear charge is defined as the net positive charge experienced by an electron in a multielectron atom. The higher the atomic number, the higher is the nuclear charge. Silicon has 14 protons while aluminium has 13 protons. Hence, silicon has a larger nuclear charge of (+14) than aluminium, which has a nuclear charge of (+13). Thus, the electrons in the 3p orbital of silicon will experience a more effective nuclear charge than aluminium.
\({ 13 }^{ Al }={ 1s }^{ 2 },{ 2s }^{ 2 },{ 2p }^{ 6 },{ 3s }^{ 2 },{ 3p }^{ 1 }\)
\({ 14 }^{ Si }={ 1s }^{ 2 },{ 2s }^{ 2 },{ 2p }^{ 6 },{ 3s }^{ 2 },{ 3p }^{ 2 }\)

In a hydrogen atom, the energy of an electron is determined by the value of n and in a multielectron atom, it is determined by n + 1. hence, for a given principal quantum, electrons of s,p,d and f-orbitals have different energy (for,p,d and f = 0,1,2 and 3 respectively).

\(2A+4B\longrightarrow 3C+4D\)
According to the given reaction, 2 moles of A rect with 4 moles of B.
Hence, 5 moles of A will react with 10 moles of
\(b\left( \frac { 5\times 4 }{ 2 } =10moles \right) \)
Limiting reagent decide the amount of product produced. According to the reaction, 4 moles of B produces 3 moles of C.
6 moles of B will produce\(\frac { 3\times 6 }{ 4 } =4.5\) moles of C.