List of top Chemistry Questions

Answer the following case-based questions on biomolecules: \[ (a)\;\text{Write the name of basic building units of proteins and nucleic acids. How can you differentiate between fibrous and globular proteins on the basis of their structures?} \] \[ (b)(i)\;\text{What products would be formed when a nucleotide from DNA containing thymine is hydrolyzed?} \] OR \[ (b)(ii)\;\text{Write one structural difference between DNA and RNA.} \] \[ (c)\;\text{Give one example each of a fat-soluble vitamin and a water-soluble vitamin.} \]

An antifreeze solution is prepared by dissolving \(31g\) of ethylene glycol \((M=62g\,mol^{-1})\) in \(600g\) of water. Calculate the freezing point of the solution. \[ K_f\text{ for water}=1.86K\,kg\,mol^{-1} \]

Give reasons for the following: \[ (a)\;\text{Although chlorine is an electron-withdrawing group, yet it is ortho-, para-directing in electrophilic aromatic substitution reactions.} \] \[ (b)\;\text{Aryl halides cannot be prepared by reacting phenol with concentrated halogen acids or phosphorus halides.} \] \[ (c)\;\text{Chloroform is stored in closed dark coloured bottles.} \]

Answer the following questions about the complexes \([NiCl_4]^{2-}\) and \([Ni(CN)_4]^{2-}\): \[ (i)\;\text{Write the hybridization involved in each case.} \] \[ (ii)\;\text{Which of them is the inner orbital complex and which one is the outer orbital complex?} \] \[ (iii)\;\text{Compare their magnetic behaviour.} \] \[ \text{Atomic number: }Ni=28 \]

How do you explain the following? \[ (a)\;\text{Presence of a straight chain in glucose} \] \[ (b)\;\text{Presence of five }-OH\text{ groups in glucose which are attached to different carbon atoms} \]

The half-life period of a radioactive element is \(1.5\times 10^{10}\) years. Calculate the time in which the activity of the element is reduced to \(75\%\) of its original value. \[ \text{Given: }\log 2=0.30,\quad \log 3=0.48,\quad \log 4=0.60 \]

State Kohlrausch's law of independent migration of ions. With the help of a curve, explain why it is not easy to determine \(\Lambda_m^\circ\) for weak electrolytes by extrapolating the concentration--molar conductivity curve, as it is for strong electrolytes.

For a reaction \(A+B\rightarrow\) products, the rate law is: \[ Rate=k[A][B]^{\frac{3}{2}} \] Write the overall order of the reaction. Can this reaction be an elementary reaction? Give reason.

Explain why, on addition of 1 mol of KCl to 1 litre of water, the boiling point of water increases, while addition of 1 mol of methyl alcohol to 1 litre of water decreases the boiling point.

Write IUPAC names of the following coordination compounds:
(i) [PtCl_2(en)_2]SO_4
(ii) (NH_4)_2[CoF_4]

Assertion (A): Aromatic primary amines cannot be prepared by Gabriel phthalimide synthesis. Reason (R): Gabriel phthalimide synthesis is used for the preparation of primary aliphatic amines.

Assertion (A): Order of reaction is applicable to elementary as well as complex reactions. Reason (R): Order of a reaction is an experimental quantity.

For the compound having molecular formula \(C_4H_9Br\), write:
(a) the isomer which is most reactive towards S_N1 displacement.
(b) the isomer which, on reacting with Na metal in dry ether, gives 2,5-dimethylhexane.

Assertion (A): Separation of Zr and Hf is difficult. Reason (R): Because Zr and Hf lie in the same group of the periodic table.

On hydrolysis, which of the following carbohydrates gives only glucose?

Assertion (A): Phenol is less acidic than 4-methylphenol. Reason (R): The presence of an electron releasing group in phenol makes it less acidic.

The mole fraction of a solute in \(2.0\) molal aqueous solution is:

For a reaction \(3A \rightarrow 2B\), the rate of reaction \(+\dfrac{d[B]}{dt}\) is equal to:

On electrolysis of very dilute aqueous solution of NaCl using platinum electrodes:

Among the following, which is the strongest base?

The boiling point of an azeotropic mixture of water and ethanol is less than that of pure water and ethanol. The mixture shows:

In aqueous solution, \(Cr_2O_7^{2-}\) ion converts to which of the following in alkaline medium?

According to Werner's theory, the primary valencies of the central metal atom:

Which of the following reagent is used to distinguish between \((C_2H_5)_2NH\) and \((C_2H_5)_3N\)?

The oxidation number of Co in \([Co(en)_3]_2(SO_4)_3\) is: