In DNA and RNA, nitrogen atom is present in the ring system. Can Kjeldahl method be used for the estimation of nitrogen present in these? Give reasons.
DNA and RNA have nitrogen in the heterocyclic rings. Nitrogen present in rings, azo and nitro groups cannot be converted into $\left(\mathrm{NH}_4\right)_2 \mathrm{SO}_4$. That's why Kjeldahl method cannot be used for the estimation of nitrogen present in DNA and RNA.
If a liquid compound decomposes at its boiling point, which method (s) can you choose for its purification. It is known that the compound is stable at low pressure, steam volatile and insoluble in water.
If a compound decomposes at its boiling point but is steam volatile, water-insoluble and stable at low pressure, steam distillation can be used for its purification. This technique is applied to separate substances which are steam volatile and immiscible with water.
"Stability of carbocations depends upon the electron releasing inductive effect of groups adjacent to positively charged atom involvement of neighbouring groups in hyperconjugation and resonance."
Draw the possible resonance structures for 
and predict which of the structures is more stable. Give reason for your answer.
The given carbocation has two resonance structures.
Structure (II) is more stable because both the carbon atoms and the oxygen atom have an octet of electrons.
"Stability of carbocations depends upon the electron releasing inductive effect of groups adjacent to positively charged atom involvement of neighbouring groups in hyperconjugation and resonance."
Which of the following ions is more stable? Use resonance to explain your answer.
Carbocation $(A)$ is more stable than carbocation (B). Carbocation. $(A)$ is more planar and hence is stabilised by resonance while carbocation (B) is non-planar and hence it does not undergo resonance. Further, double bond is more stable within the ring in comparison to outside the ring.
"Stability of carbocations depends upon the electron releasing inductive effect of groups adjacent to positively charged atom involvement of neighbouring groups in hyperconjugation and resonance."
The structure of triphenylmethyl cation is given below. This is very stable and some of its salts can be stored for months. Explain the cause of high stability of this cation.
In triphenylmethyl cation, due to resonance, the positive charge can move at both the $o-$ and $p$-position of each benzene ring. This is illustrated below
Since, there are three benzene rings, hence, there are, in all, nine resonance structures. Thus, triphenylmethyl cation is highly stable due to these nine resonance structures.