Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

Complete the following:

\[\ce{C6H5NO2 ->[Sn/HCl] A ->[Br2/H2O] B ->[NaNO2/HCl][273 - 278 K] C ->[HBF4][Δ] D}\]

KMnO₄ is coloured due to ______.

The CFSE of [CoCl₆]^3– is 18000 cm^–1 the CFSE for [CoCl₄]^– will be ______.

Give reason for the following:

During the electrophilic substitution reaction of haloarenes, para-substituted derivative is the major product.

Give reasons for the following observation:

Aniline is acetylated before nitration reaction.

Give reasons for the following observation:

Aniline does not react with methyl chloride in the presence of anhydrous AlCl₃ catalyst.

Write the reaction occurring at anode and cathode and the products of electrolysis of aq KCl.

Why \[\ce{HCl}\] should not be used for potassium permanganate titrations?

What is the effect of pH on dichromate ion solution?

Using crystal field theory, write the electronic configuration of d⁵ ion, if Δ₀ > P.

What is the spectrochemical series?

What is the difference between a weak field ligand and a strong field ligand?

What is crystal field splitting energy?

Why tryptophan is an essential amino acid?

Complete the following ionic equation:

\[\ce{Cr2O^{2-}7 + 2OH^- ->}\]

Assertion (A): Chlorobenzene is resistant to electrophilic substitution reaction.

Reason (R): C-Cl bond in chlorobenzene acquires partial double bond characters due to resonance.

Four half-reactions, I to IV are shown below:

1. \[\ce{2Cl^- -> Cl2 + 2e^-}\]
2. \[\ce{4OH^- -> O2 + 2H2O + 2e^-}\]
3. \[\ce{Na^+ + e^- -> Na}\]
4. \[\ce{2H^+ + 2e^- -> H2}\]

Which two of these reactions are most likely to occur when concentrated brine is electrolysed?

In the two tetrahedral structures of dichromate ion, ______.

How can the activating effect of the −NH₂ group in aniline be controlled?

On the basis of Crystal Field theory, write the electronic configuration for the d⁵ ion with a strong field ligand for which Δ₀ > P.