List of top Chemistry Questions

Draw the structure of the semicarbazone of acetone.

\[ \text{A black-brown coloured solid }(A)\text{ when fused with }KOH\text{ in the presence of air, produces a dark green compound }(B)\text{ which on electrolytic oxidation in alkaline medium gives a dark purple coloured compound }(C).\text{ Identify }(A),(B)\text{ and }(C).\text{ Write the reactions involved.} \]

Name two coordination compounds which are important in biological systems.

Define Ambidentate Ligand with one example.

Calculate emf of the following cell at \(298\,K\) : \[ Cr(s)\,|\,Cr^{3+}(aq,\;0.1\,M)\,||\,Fe^{2+}(aq,\;0.01\,M)\,|\,Fe(s) \] (Given : \[ E^\circ_{Cr^{3+}/Cr}=-0.74\,V, \] \[ E^\circ_{Fe^{2+}/Fe}=-0.44\,V, \] \[ \log 10 = 1 \] )

The rate of the chemical reaction doubles when the temperature is raised from \(298\,K\) to \(308\,K\). Calculate activation energy \((E_a)\) for this reaction assuming that it does not change with temperature. (Given : \(R = 8.314\,J\,mol^{-1}\,K^{-1}\), \(\log 2 = 0.30\))

Assertion (A) : All aliphatic aldehydes give a positive Fehling’s test. Reason (R) : Aliphatic aldehydes are reduced by Fehling’s reagent.

Assertion (A) : Highest oxidation state of Mn is +7 in first series of transition elements. Reason (R) : Transition metals exhibit variable oxidation states.

Assertion (A) : p-nitrophenol is more acidic than phenol. Reason (R) : Nitro group is an electron-withdrawing group, it stabilises phenoxide ion by dispersal of negative charge.

Primary, secondary and tertiary alcohols can be distinguished by :

Which of the following ligands forms a chelate complex ?

Identify the polysaccharide among the following :

The polypeptide chain in a protein has amino acids linked with each other in a specific sequence. This specific sequence of amino acids is called :

Consider the following compounds : \[ C_2H_5NH_2,\quad (C_2H_5)_2NH,\quad C_6H_5CH_2NH_2,\quad NH_3,\quad C_6H_5NH_2 \] The correct increasing order of the above compounds on the basis of their basic strength is :

Assertion (A) : D (+) – Glucose is dextrorotatory in nature. Reason (R) : (+) represents dextrorotatory nature and D represents the configuration.

Consider the following reaction and identify A and B : \[ CH_3Cl + NaI \xrightarrow[\text{dry acetone}]{} A + B \]

Half-life (\(t_{1/2}\)) of a first order reaction is 1386 s. The value of rate constant is :

Actinoids show larger number of oxidation states :

The correct formula of Hinsberg’s reagent is :

The major product of carbylamine reaction is :

Which of the following reagents are used to prepare primary amines by Hoffmann bromamide degradation reaction ? \[ (i)\quad \begin{array}{c} O\\ || \end{array} R-C-NH_2 \] \[ (ii)\quad NaOH \] \[ (iii)\quad Br_2 \] \[ (iv)\quad CHCl_3 \]

Which of the reactions is used in the conversion of a ketone into hydrocarbon ?

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. \[ \text{Given : } \log 2 = 0.30,\; \log 3 = 0.48,\; \log 4 = 0.60 \]

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.

An antifreeze solution is prepared by dissolving 31 g of ethylene glycol (Molar mass = 62 g mol$^{-1}$) in 600 g of water. Calculate the freezing point of the solution. (K$_f$ for water = 1.86 K kg mol$^{-1}$)